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3D-printed artefacts are becoming more common, and the effect of printing parameters on their properties is key to their performance in applications. Although parameters like build orientation and raster direction are well-studied the effect of layer thickness is less well-known. This study determines the influence of layer thickness on the mechanical properties of polylactic acid (PLA) and acrylonitrile butadiene styrene (ABS) 3D printed specimens made with fused filament fabrication (FFF). Samples were printed with differing layer thicknesses and tensile tested according to ASTM D638. The study also found that when increasing the layer thickness the mechanical properties of the specimens for both ABS and PLA decreased. When it came to ultimate tensile strength, the effect of layer thickness on PLA was more significant than on ABS. Considering the mechanical properties as well as aspects such as printing time and simplicity of printing, an optimum print setting could be determined. The study found that PLA was more significantly affected by the change in layer thickness compared to ABS. [ABSTRACT FROM AUTHOR]

Currently, in pipe welding, it is nearly difficult for a human welder to weld the whole circumference of a pipe in a single uninterrupted pass using MIG welding causing inconsistencies in weld quality around the welded pipe. The aim of this study was to develop an automated orbital pipe MIG welding system and to optimize welding parameters for enhancing ultimate tensile strength and Rockwell hardness of mild steel 1020 grade pipe. Three levels of variation were applied to the four input parameters that were chosen. Nine experiments were carried out using orthogonal array of L9. In this experimental investigation, the highest ultimate tensile strength (UTS) of 411.2 MPa and Rockwell hardness (RH) of 95 HRB were achieved at 110 A of current, 24 V of voltage, welding gun travel speed of 30 cm/min, and 3 mm of arc length. For modeling the orbital pipe MIG welding process experimental input parameters and response results, a hybrid artificial neural network and genetic algorithm (ANN-GA) model was constructed. This model was used to forecast and optimize UTS and RH, as well as the process factors that go with it. The results indicated that the ANN-GA model could predict the output responses with a mean square error of 5.06e-05. During optimization, a 4–9-2 network trained with neural network of back propagation by Bayesian regularization approach was determined to have the greatest prediction capability, with maximum UTS and RH of 417.857 MPa and 96.5364 HRB, respectively. From the confirmation tests, the average results of 412.7 MPa of UTS and 95 HRB of HR were obtained. The percentage of errors between the ANN-GA predicted optimal responses' results and the confirmatory experimental results were found 1.23% and 1.59% for UTS and RH, respectively. [ABSTRACT FROM AUTHOR]

This research aims to evaluate Al-Al joints fabricated by overcasting liquid 2024 Al alloy onto Zn-electroplated 2024 Al alloy solid inserts followed by solidification under pressure. The effects of three most influencing process parameters including squeeze pressure, die temperature and melt temperature on the mechanical properties of as-casted and aged overcast joints were investigated. Response surface methodology with central composite design was employed for experimental design and development of empirical models. The observed responses in this research include ultimate tensile strength and hardness. Adequacy and validity of the developed models were verified through ANOVA and confirmation experiments, respectively. For both as-casted and aged overcasting conditions, the results revealed melt temperature as the most significant process parameter affecting ultimate tensile strength and hardness followed by die temperature and squeeze pressure. The comparative analysis of the two conditions suggested aged overcasting as the better alternative which resulted in 5.7~9.8 and 3.6~12.4% improvement in ultimate tensile strength and hardness, respectively. [ABSTRACT FROM AUTHOR]

Typical additive manufacturing (AM) processes for producing metal and ceramic parts are highly energy-consuming and expensive to install and maintain. On the other hand, material extrusion AM (MEAM) technologies are conventionally used to produce polymeric parts but only marginally to process metallic materials. A feasible alternative is to process polymeric filaments loaded with metal particles. Debinding and sintering processes are then required to join the metal particles and obtain the final parts. In recent years, highly filled metal filaments consisting of a polymer loaded with a high concentration of metal powder have been commercialized for this purpose. In this study, the printability of a commercial CuSn12 filament was investigated by evaluating the influence of the process parameters on the density, shrinkage, porosity, and mechanical properties of the additively manufactured samples using a low-cost desktop 3D printer. Parameters such as the flow rate and ironing had the greatest influence on the density of the green samples. The correct selection of these parameters may reduce shrinkage after sintering. Furthermore, the obtained bronze had a notable ultimate tensile strength (mean value of 107 MPa), high stiffness (E values range from 38 to 50 GPa), and a greater elongation at break (mean value of 13%) than that of cast bronze of the same CuSn12 type. In this case, the extrusion pattern and ironing had the most significant influence on the final mechanical performance. The study provides insights into the use of highly filled bronze filaments combined with MEAM to produce functional parts for engineering applications. [ABSTRACT FROM AUTHOR]

This study proposed the direct extrusion and continuous-shear deformation (DECS) process for the co-extrusion of Mg-AZ31B/Al 6063, aiming to prepare high-plasticity Mg/Al composite sheets. The effect of extrusion temperature on the microstructure and mechanical properties of the Mg/Al composite sheet was systematically studied. The results show that Mg/Al composite sheets with no voids or cracks at the interface were successfully prepared by the DECS process. The microstructure of the Mg layer at different extrusion temperatures primarily consists of equiaxed fine grains, with grain sizes of 7.29 μm, 8.98 μm, and 9.88 μm at 330℃, 360℃, and 390℃, respectively. The Mg layer exhibits a typical extrusion texture, with the c-axis of most grains parallel to the transverse direction (TD). With the increase in extrusion temperature, the c-axis of some grains deviates from the TD toward the normal direction (ND). The Al layer mainly consists of elongated deformed grains and fine dynamically recrystallized (DRXed) grains distributed along the extrusion direction (ED). The AZ31 Mg alloy with refined grains maintains the ultimate tensile strength of the Mg/Al composite sheet, while the Al matrix enhances its plasticity. At 330℃, the Mg/Al composite sheet shows an ultimate tensile strength of 244.48 MPa ± 4.35 and an elongation of 39.42% ± 0.06. The influence of the bonding layer thickness on the shear and tensile properties of the composite sheet was studied, revealing that increasing the bonding layer thickness reduces the shear strength of the Mg/Al composite sheet but positively affects its tensile strength. [ABSTRACT FROM AUTHOR]

Investigations of the rolling modes of plates from an experimental aluminum-magnesium alloy with a scandium content of 0.10–0.11 wt.%, corresponding to the chemical composition of the 1580 alloy, were carried out in laboratory and industrial conditions. It has been found that alloying of this material with scandium within the indicated limits leads to a significant grain refinement in the cast ingot and an increase in the strength properties of deformed semi-finished products. Based on the results of physical modeling of the rolling process, rational reduction modes are proposed, which made it possible to obtain deformed semi-finished products with the required level of mechanical properties. Based on the results of physical and computer modeling of the rolling process, rational reduction modes are proposed for pilot studies, which made it possible to obtain deformed semi-finished products with the required level of mechanical properties. At the same time, the power parameters of rolling did not exceed the allowable values of the force and rolling moment for the QUARTO 2800 rolling mill. To assess the formation patterns of the metal structure necessary to obtain high-quality plates, a metallographic analysis of the structure of cast and deformed semi-finished products from an experimental alloy was carried out. The results were used to test the reduction modes during sheet rolling and to adjust the casting parameters of experimental ingots. Annealing has practically no effect on the level of mechanical properties of plates obtained under production conditions in a hot-deformed state, while the ultimate tensile strength in the longitudinal direction is 388–389 MPa, the yield strength is 245–247 MPa, and the elongation to failure is 18.0–18.8%. After cold rolling, the plates have the following mechanical properties: ultimate tensile strength 413–414 MPa, yield strength 386–372 MPa, and elongation to failure 5.2–6.6%. Based on the results of the research, recommendations were formulated for the development and implementation of an industrial technology for rolling plates from alloy 1580 with a thickness of 31.5–45 mm from ingots with a thickness of 300–450 mm. [ABSTRACT FROM AUTHOR]

The primary purpose of this research is investigating the effect of increasing temperature on mechanical properties and formability of Al 5083 produced by equal channel angular rolling (ECAR) process. The present work also aims to study the feasibility of increasing temperature as an approach for solving the ductility problem of ultrafine-grained Al 5083, although some strength of the material might be sacrificed. So, the quantitative and qualitative analysis of the effect of temperature increase on mechanical properties and formability has been done. In this paper, the ECAR process has been performed at three different temperatures (i.e., 25 °C, 200 °C, and 300 °C(. Then, the investigation of mechanical properties such as yield strength, ultimate tensile strength, and microhardness after each pass of the ECAR at different temperatures has been performed. The results showed that by applying the ECAR process at a specified temperature, the mechanical and microhardness properties of the samples improved, while elongation to fracture reduced. At ambient temperature, and after the 3rd pass of the ECAR process, yield strength, ultimate tensile strength, and microhardness compared with the annealed sample increased by 94%, 19%, and 52%, respectively. Also, the mechanical properties of samples after the ECAR process in a specified pass at different temperatures have been evaluated. The obtained results showed that by increasing temperature, the yield strength, ultimate tensile strength, and microhardness of the samples decreased, but the elongation to fracture as well as the forming limit diagram (FLD) improved. The results illustrated that by applying the ECAR process at a specified temperature, the level of the FLDs moved downward. Also, the FLDs after the 3rd pass of the ECAR at different temperature have been compared. The results showed that the FLD0 (the major forming limit strain in-plane strain mode) at a temperature of 200 °C and 300 °C compared with the ambient temperature increased by 5% and 20%, respectively. [ABSTRACT FROM AUTHOR]

Submerged arc welding (SAW), renowned for its high deposition rate and superior weld quality, is the go-to method for joining thick metals in heavy structures. However, industry beams and columns welded with SAW can exhibit detrimental defects like undercut, porosity, and burn-through, significantly impacting weld properties. This study addresses this challenge by presenting a multi-objective optimization approach for SAW parameters on AISI 1020 mild steel. Aiming to optimize tensile strength, hardness, and bead width, the study employs Taguchi's design of experiments and couples the multi-objective Jaya algorithm with an artificial neural network (ANN). This synergistic combination yielded optimal process parameters: 417 A welding current, 20.7 mm electrode stick-out, 33.7 V voltage, and 505.8 mm/min transverse speed. These settings translated into exceptional weld characteristics, with ultimate tensile strength reaching 427 MPa, hardness of 73.9 HRB, and bead width of 14.29 mm. Confirmation tests further validated these findings, demonstrating minimal error and solidifying the effectiveness of the optimization approach. This research paves the way for enhanced weld quality and process control in heavy structural applications. [ABSTRACT FROM AUTHOR]

This paper investigates the mechanical properties of AA2024 joints welded using the Friction Stir Welding (FSW) process, with a particular focus on comparing joints made with and without the inclusion of a commercially pure copper sheet between the edges being welded. The study aims to understand the influence of weld heterogeneity on the mechanical properties of FSW joints. Various joints were fabricated with a copper interlayer, and optimal process parameters—rotational speed, advancing feed, and tool geometry—were identified. Mechanical tests, including Rockwell B and Vickers hardness (HV) tests, as well as tensile tests, were conducted on both homogeneous and heterogeneous joints. The results showed that the presence of copper significantly affected the hardness distribution, particularly in the weld nugget. Heterogeneous joints demonstrated a notable increase in HV at the nugget and a reduced weld-affected area on both the advancing and retreating sides. The study found a strong correlation between process parameters, tool geometry, and the Ultimate Tensile Strength of the joints. Optimal mechanical properties were achieved in heterogeneous joints welded at 800 rpm and 40 mm/min with an 18 mm tool, resulting in a joint efficiency of 73%. These parameters differed significantly from those optimized for homogeneous joints, which were 1200 rpm and 100 mm/min with a 16 mm tool. It was also observed that exceeding 1000 rpm in rotational speed and 70 mm/min in feed speed is not advisable for heterogeneous welds. Future research should explore varying amount of copper and other materials, as well as different interposition methods, to further understand their effects on the mechanical properties of FSW joints. [ABSTRACT FROM AUTHOR]

Nowadays, H13 steel is commonly utilized in processes such as pressure die casting, extrusion, and drop forging as well as in tube and glass manufacturing, however with limited manufacturability. The current research focuses on the effects of crucial process-related additive manufacturing parameters on the mechanical behavior of H13 hot work tool steel manufactured by the selective laser melting (SLM) additive manufacturing (AM) technique. The investigated parameters were the scan speed, the laser power, and their output volumetric energy density (VED) on the mechanical and morphological properties utilizing tensile and nanoindentation tests as well as scanning electron microscope (SEM). The results of this study revealed that it is possible to manufacture H13 steel parts with high mechanical performance using the SLM additive manufacturing technique. Specifically, the ultimate tensile strength reached a peak value at 1836 ± 48 MPa, while the yield tensile strength was found at 1468 ± 30 MPa. These parts are comparable to those made with conventional materials. A die part made using SLM was tested in the aluminum extrusion process on an 18 MN extrusion press producing acceptable quality extrudates and verifying its functionality and resilience under the high pressure and temperature of the extrusion process. [ABSTRACT FROM AUTHOR]

In friction stir welding, geometrical and motion features of the tool or pin greatly influence the interaction between the tool and workpiece as well as the resulting joint microstructure and mechanical properties. In order to enhance the material flow by optimizing the tool geometrical features, a new strategy was proposed in this study to introduce eccentric motion by offsetting the pin from the tool shoulder, and thin Al–Mg-Si aluminum alloy plates were friction stir welded by varying the pin eccentricity. The material flow and mixing characteristic were analyzed by optical microscope and tracer material method. The grain size and micro-texture of the stir zone were analyzed by electron backscatter diffraction. Uniaxial tensile tests and digital image correlation were conducted to evaluate the mechanical properties and observe the in situ strain evolution. The results show that pin eccentricity has a positive effect on promoting the material flow and grain refinement in the stir zone. The texture intensity was increased as pin eccentricity was introduced, and the dominant texture component converted from C {001} < 110 > (without eccentricity) to B / B ¯ {112} < 110 > when eccentric pin was used. However, no discerning change can be seen in the thermal history between samples. Despite the variation in softening of the stir zone with eccentricity, the ultimate tensile strength change was negligible. The average ultimate tensile strength reached approximately 198 MPa regardless of the pin eccentricity, and all joints fractured at the heat-affected zone. However, the softened stir zone caused by pin eccentricity resulted in an obvious increase in the joint elongation. It can be concluded that pin eccentricity significantly improved the material flow and grain refinement in the stir zone as well as enhanced the toughness of the weld joint. [ABSTRACT FROM AUTHOR]

Lightweight bent aluminum profiles are widely utilized in transportation fields. In this paper, the torsional channel self-bending extrusion process (TCSE) was adopted to machine AA6063 bent aluminum profiles in a single operation to verify the process's feasibility. Effects of extrusion parameters on the curvature, microstructure, and mechanical properties of the profiles were researched, and the extrusion process was simulated. The results show that the extruded profiles had good curvature stability. The grains were equiaxed in the cross longitudinal section, and the grain size at the outside diameter (OD) position was smaller than the inside diameter (ID) position. When the difference in deformation temperature at the OD edge was above 31 K, a smaller peripheral coarse grain (PCG) layer was formed at the OD edge with a thickness of about 400 μm, resulting in reduced hardness. The Mg2Si particles served as the main strengthening phase, which increased in number and decreased in size with increasing billet temperature and extrusion speed. Increasing the billet temperature and speed improved the mechanical properties of the material, with an increase in average hardness of 55.9% and 19.5%, and ultimate tensile strength (UTS) of 12.5% and 7.1%, respectively. By comprehensively considering the factors of extrusion load, microstructure, and mechanical properties, the optimum bent profile for different curvatures was determined. When a large curvature (≥328.67 mm) was required, it was preferred to increase the billet temperature. When a smaller curvature (≤328.67 mm) was required, it was advisable to increase extrusion speed. [ABSTRACT FROM AUTHOR]

In the present work, the effect of build-up orientation angle and printing speed on mechanical properties of 17-4 PH stainless steel components realized by Bound Metal Deposition technology was investigated. Furthermore, the presence of microscopical and macroscopical defects was analyzed as a function of the printing parameters investigated. To this purpose, tensile specimens, printed with different build-up orientation angles (0°, 45°, and 90°) and printing speeds (15, 30, 45, and 60 mm/s), were tested at room temperature to evaluate the mechanical properties as a function of the process parameters. Furthermore, stereo optical microscopy and scanning electron microscopy coupled to energy dispersive X-ray spectroscopy were used, respectively, to observe the macroscopical and microscopical defect presence on the 3D printed parts built with different build-up orientation angles and printing speeds. It was demonstrated that the build-up orientation angle and printing speed significantly affect the mechanical properties and the surface finish of 3D printed components, as well as the presence of micro-defects due to the layer-by-layer filament deposition. In particular, the build-up orientation angle of 45° confers less mechanical to the specimens than the other two orientations investigated, both in terms of ultimate tensile strength, yield strength, and modulus of elasticity. Furthermore, high print speeds do not significantly contribute to a worsening of mechanical performance but influence the surface finish which is characterized by greater printing defects. [ABSTRACT FROM AUTHOR]

This paper investigates the cold spray additive manufacturing of a thick wall made of pure Al powder with a granulometry of + 45–15 μm with a size d50 = 26.95 µm. A high wall with vertical lateral faces is obtained without clogging, using a compensation building strategy and gas pressurization at 30 bars, 400°C. Layer by layer, using a suitable set of deposition parameters, the profile of the deposit grows without a lack of material at the lateral edges and then produces the near-net shape 3D wall. However, a structural characterization shows an issue of pore development and low mechanical properties. A porosity with a typical pore size range of 6–100 µm is observed from the bottom zone to the top zone of the wall, with a random occurrence and with a fraction of pores up to 8%. The distribution of the pore size shows a high fraction of fine pores (6–10 µm) up to ~ 70%. There can be a weak fraction (~ 0.04%) of larger pores (130–200 µm) and such pores appear as a continuous connexion of pores within the deposit due to a bad stacking and a bad bonding of particles during the additive growth. These detrimental defects ease the brittle mechanical behaviour of the wall during a tensile test. An intergranular-like fracture is observed with some trace of dimples but the brittle stress/strain curve until rupture suggests a predominant failure by cleavage due to the porosity. The fracture strain is less than 2%. The ultimate tensile strength and the elastic modulus are limited to about 50 MPa and about 50 GPa, respectively. [ABSTRACT FROM AUTHOR]

This work is an attempt to fabricate aluminum (AA 5049) matrix composites (AMCs) reinforced with electrospun polyacrylonitrile (PAN) nanofibers and consisting of exfoliated graphite nanosheets (EGNS/PAN) by utilizing friction stir processing (FSP) to improve the mechanical characteristics of AA 5049. The electrospinning method was used for fabricating PAN and EGNS/PAN nanofibers. The average diameter of the electrospun PAN nanofibers is 195 ± 57 nm, and after EGNS incorporation is 180 ± 68 nm. Dynamic recrystallization was the main process in the microstructure evolution of the stir zone during the FSP with PAN and EGNS/PAN nanofibers. According to PAN and EGNS/PAN nanofibers were used in the FSP procedure, the grain size reduced as a result of the pinning effects. PAN and EGNS/PAN nanofiber reinforcement enhanced the hardness to 89 and 98 Hv, respectively. Also, the ultimate tensile strength was raised to 291 MPa and 344 MPa, respectively. Tensile strength and hardness of the stir zone increased during the FSP with PAN and EGNS/PAN nanofibers due to the higher density of the strengthening mechanisms of grain boundaries and dislocations. The mechanical characteristics of AA5049 can be enhanced by the procedure of incorporating nanofibers, making them an ideal choice for applications in the automotive and aerospace industries. [ABSTRACT FROM AUTHOR]

This research aims to investigate the effects of as-casted and proposed in situ heat-treated squeeze casting of Al-3.5 % Cu alloy. The effects of squeeze pressure, melt temperature and die temperature on ultimate tensile strength, percentage elongation and hardness were modelled and analysed for as-casted and in situ heat-treated squeeze casting using the Box-Behnken design. Response surface methodology was used for experimental design, empirical modelling and analysis. Adequacy and validation of the developed models were verified using ANOVA and confirmation experiments, respectively. The results revealed squeeze pressure as the most significant input variable followed by die temperature under as-casted and in situ heat-treated squeeze casting conditions. The comparative analysis suggested in situ heat-treated squeeze casting conditions as the best alternative which resulted in 7.9~11, 6.7~25.7, and 2.2~7.7 % improvement for ultimate tensile strength, percentage elongation and hardness, respectively. A considerable increase in mechanical properties provided a great evidence to reveal a new technique for foundry men to enhance the quality of squeeze casted Al-Cu alloys. Furthermore, the empirical model will aid practitioners to predict the desired mechanical properties prior to examination. [ABSTRACT FROM AUTHOR]

Friction surfacing (FS) is a solid-state layer deposition process for metallic materials at temperatures below their melting point. While the bonding of the deposited layers to the substrate is proven suitable for coating applications, so far the mechanical properties of additively manufactured stacks have not been systematically investigated. In particular, the effect of successive deposited FS layers, i.e., repetitive thermo-mechanical loading, on the interface properties as well as anisotropy and strength of the deposited stack is unknown. For this purpose, the mechanical properties of FS deposited multi-layer stacks from dissimilar aluminum alloys have been investigated, characterizing layer-to-layer as well as layer-to-substrate bonding interfaces via micro-flat tensile testing. Furthermore, directional dependencies in the stack and failure mechanisms are analyzed. The results show a homogeneous, fine-grained microstructure with average grain sizes between 4.2 and 4.6 μ m within the deposited material. The resulting tensile properties with no significant directional dependency present an ultimate tensile strength between 320 and 326 MPa exceeding the strength of the AA5083 H112 consumable base material. No difference was obtained in terms of layer-to-layer or layer-to-substrate interface strength. Furthermore, homogeneous hardness was observed within the deposited structure, which is in the range of AA5083 base material's hardness of 91 HV. The results indicate that the FS process in conjunction with the material used is suitable for additively generated structures and highlight the potential of this solid-state layer deposition technology. [ABSTRACT FROM AUTHOR]

The rheological, mechanical, and electrical properties and structure of rods and wires made of aluminum alloy concentration of 1% REM (0.6% Ce and 0.4% La) are investigated and presented. The rods were produced by combined rolling-extrusion (CRE) from two different types of billets: casting into a mold 14×14 mm and into electromagnetic mold (EMM) Ø12.5 mm. A database of the DEFORM 3D complex was created for computer modeling of the CRE process. The tensile strength of rods Ø9 and 5 mm obtained using CRE method is 120–140 MPa and elongation to failure is 15–26% for billets from EMM. For billets 14×14 mm, the ultimate tensile strength is 112–125 MPa, which is comparatively lower than that of rods made from round billets (elongation to failure is 26–34%). The plastic properties of the final wire Ø2 mm from a round billet after EMM are higher than wire Ø2 mm from a billet obtained by casting into a mold 14×14 mm. Rods after CRE from both types of billets are characterized by fairly high ductility. To obtain Ø2-mm wire from rods, no intermediate annealing was required. The values of electrical resistance are taken from 0.02271 to 0.0301 Ω‧mm2/m for rods from 12.5-mm billets and from 0.02776 to 0.03413 Ω‧mm2/m for rods from billets 14×14 mm. The electrical resistance values for wire Ø2 mm from billets 14×14 mm are higher than for wire obtained from rods after EMM. Microstructure shows that the final wire after CRE from billet in EMM has a more extensive structure than after CRE from billets with dimensions of 14×14 mm. [ABSTRACT FROM AUTHOR]

The joining of titanium and stainless steel is challenging with conventional filler metals due to the formation of Fe-Ti intermetallic compounds (IMCs). Therefore, a filler that is compatible with both metals is necessary to avoid these IMCs and enhance the mechanical properties of Ti-SS joint. This research aims to investigate the effect of novel Nb-Cu composite filler on mechanical and microstructure properties of TA7-SS304 dissimilar hybrid composite joints using gas tungsten arc welding (GTAW) process. The mechanical properties: ultimate tensile strength (UTS) and micro hardness have been analyzed and assessed through the microstructure of weld interfaces and fracture zones. Results revealed that welding current (I) affects the UTS significantly whereas micro hardness is greatly influenced by welding speed (Ws). The maximum UTS of 293 MPa and micro hardness of 100 HV as well as minimum tensile residual stresses of 180 MPa and 170 MPa on SS 304 and TA7 sides, respectively have been attained at optimal parameters of I = 40 A, Ws = 150 mm/min and GFR = 18 lit/min. SEM and EDS analysis showed that presence of Cu and Nb solid solutions in the fusion zone contributed to improvement in UTS. Ductile fracture surface with no prominent defects is obtained at optimal combination, while brittle fracture with voids and cavities is observed for low-strength joints. X-ray diffraction analysis depicted that the formation of TiFe, Ti2Fe, and TiFe2 compounds and direct mixing of base metals have been successfully inhibited by using Nb-Cu composite filler which improved the Ti-SS bonding. [ABSTRACT FROM AUTHOR]

Dissimilar weldments of AISI 316 and Monel 400 are extensively used in boiler feed water heaters where the weld roots are exposed to high pressure and hot corrosive environments. In this research, metallurgical and mechanical properties of dissimilar weldments of AISI 316 and Monel 400 obtained by pulsed current gas tungsten arc welding (PCGTAW) and constant current gas tungsten arc welding (CCGTAW) processes were compared. The heat input rate and filler wire were same in both welding techniques. Metallurgical properties are studied by employing optical microscope (OM) and scanning electron microscope (SEM). Mechanical properties of dissimilar weldments are determined by tension test and Vickers hardness. The metallurgical study has revealed fine grain structures with clear grain boundaries at the heat-affected zone in PCGTAW weldment. The ultimate tensile strength in PCGTAW and CCGTAW weldments was observed as 554 and 542 MPa, respectively. The ratio of yield strength to ultimate tensile strength is higher in PCGTAW weldment than CCGTAW weldment. The weldment developed by using PCGTAW technique has shown a higher microhardness value at HAZ of both the base metals than the weldment developed in CCGTAW technique. [ABSTRACT FROM AUTHOR]

The double-pass butt welding process was carried out on 9-mm-thick 2014-T4 aluminum alloy T-joints by stationary tool shoulder friction stir welding (STS-FSW). Microstructure changes were analyzed by grain and EBSD, combined with the evolution of the precipitation phase, to explore the influence of regulations of different process parameters on T-joints' mechanical properties. Defect-free T-butt joints were obtained within the rotational speed range of 400–500 rpm and the welding speed range of 100–140 mm/min. Due to severe dynamic recrystallization, the weld nugget zone exhibits fine equiaxed grain characteristics, with a grain size of approximately 10 μm. The degree of recrystallization and deformation in the weld nugget overlapped zone (WNOZ) did not significantly change, and the grain size of WNOZ was approximately 4 μm. T-joints' hardness has an uneven distribution, and the hardness is greatest in the weld nugget zone at 110–125 HV. The T-butt joints have the weakest hardness at the skin and stringer in the TMAZ, approximately 70–80 HV. The ultimate tensile strength of the skin and stringer in the T-butt joints is equivalent to 85% and 59.6% of the base material. According to the fitting of a quadratic polynomial with multiple variables, it is found that the maximum tensile strength of the skin and stringer can only be achieved when the thermal input is within a reasonable range. The fracture is a ductile fracture with numerous dimples visible on the fracture surface. The tensile fracture of the specimen is analyzed by the finite element method. T-butt joints exhibit lower stress concentrations during the tensile test than T-fillet joints. [ABSTRACT FROM AUTHOR]

The laser-based powder bed fusion of metals (PBF-LB/M) offers a variety of advantages over conventional processing techniques and the possibility to recycle and reuse powder increases its sustainability. However, the process and resulting part properties are influenced by a variety of factors including powder recycling grade and residual oxygen content of the process atmosphere. Especially in terms of reactive materials like Ti-6Al-4V, oxidation during processing and recycling determines process stability and reproducibility. This work therefore focusses on the influence of the conventionally varied processing parameters as well as atmosphere residual oxygen content process and powder recycling on the microstructure and mechanical properties. For this purpose, the design of experiments approach is used and by evaluation of regression models, effect sizes and interactions are given. Additionally, two different etching techniques were employed to reveal different aspects of the microstructure. While no significant influence of powder recycling and residual oxygen on the microstructure could be observed, they both significantly influence the mechanical properties. A maximum hardness of 470 HV0.1, a maximum ultimate tensile strength of 1252.3 MPa, and a maximum elongation at break of 17.8 % were obtained. The results demonstrate the importance of the processing atmosphere's residual oxygen content and of taking into account the changing powder characteristics during recycling as well as its effect on the part properties. [ABSTRACT FROM AUTHOR]

Samples of AA5086 aluminium alloy were welded by gas tungsten arc welding (GTAW) with alternating current using three different shielding gases. The samples were welded with pure argon (Ar), a mixture of argon and helium (Ar + He) and a new mixture composed of argon, nitrous oxide and oxygen (Ar + N2O + O2). The effect of the shielding gas on the residual stresses and on the mechanical and microstructural properties of the welded joints was evaluated and compared with the base metal. The new gas mixture produced compressive residual stresses in the longitudinal and transverse directions in the weld metal. Tensile test of welded joints indicated similar values for yield strength and ultimate tensile strength; however, these values were lower compared to the base metal. The new gas mixture provided a welded joint with hardness values in the weld metal and heat-affected zone close to the base metal values and with greater magnitude compared to samples welded using pure argon and mixture of argon and helium. Microstructural characterisation performed by optical and scanning electron microscopy showed that the new mixture produced welded joints with lower porosity. [ABSTRACT FROM AUTHOR]

This paper studied the combined effects of matrix-to-reinforcement particle size ratio (PSR) and SiC volume fraction on the mechanical properties of extruded Al-SiC composites. A powder metallurgy technique (PM) of cold pressing at 500 MPa followed by hot extrusion at 580 °C was adopted to produce Al/SiC composite. Aluminum powder of size 60 μm and silicon carbide with different sizes, i.e., 50, 20, and 8 μm, were used. Three different volume fractions of SiC were employed, i.e., 5, 10, and 15 %, for each investigated size using a constant extrusion ratio of 14.36. The effect of matrix-to-reinforcement PSR on the reinforcement spatial distribution, fabricability, and resulting mechanical properties of a PM-processed Al/SiC composite were investigated. It has been shown that small ratio between matrix to reinforcement particle size resulted in more uniform distribution of the SiC particles in the matrix. As the PSR increases, the agglomerations and voids increase and the reinforcement particulates seem to have nonuniform distribution. In addition, the agglomerations increased as the volume fraction of the SiC increased. It has also been shown that homogenous distribution of the SiC particles resulted in higher yield strength, ultimate tensile strength, and elongation. Yield strength and ultimate tensile strength of the composite reinforced by PSR (1.2) are higher than those of composite reinforced by PSR (7.5), while the elongation shows opposite trend with yield strength and ultimate tensile strength. [ABSTRACT FROM AUTHOR]

Mechanical properties and tensile fracture behavior of normal 7075 aluminum alloy produced by rheoforming were investigated. The rheoforming applies limited angular oscillation (LAO) technique for semi-solid slurry preparation and rheological squeeze casting with transverse moving injection feed semi-solid slurry. The microstructures of as-cast rheoformed 7075 alloy are composed of fine spherical α-Al grains with average size of 26 μm surrounded by eutectic mixture. T6 heat treatment (solution treatment for 4 h at 838 K (465 °C) and aging for 12 h at 393 K (120 °C)) causes a slight increase of grain size and the formation of fine semi-coherent precipitation of η′ phase in α-Al matrix. Good elongation to fracture (10.1%, which is quite close to the wrought target (11%)) is obtained for rheoformed 7075 alloy after T6 heat treatment, with average yield strength of 461 MPa and average ultimate tensile strength of 514 MPa. Pores and voids are main defects observed in rheoformed 7075 alloy. The fracture surface of as-cast rheoformed 7075 alloy consists of large and deep dimples showing the growth and coalescence of voids. After T6 treatment, the fracture surface is composed of large dimples, flat areas containing super-fine dimples and tear ridges. Pores are present in the form of large dimples in fracture surface. The crack initiates at pores and propagates by the coalescence of pores and voids. [ABSTRACT FROM AUTHOR]

This investigation aims to make clear the relationships among geometric features, macrostructures, microstructures, and mechanical performances of the weld bead in the gas metal arc welding (GMAW) process for ASTM A606 type IV weathering steel. The results indicate that with the increase of welding heat input, the geometry of the top reinforcement and penetration increases proportionally until reaching the peak value, and then declines with the further increase of welding heat input; while the values of bottom reinforcement increase continuously with the increase of welding heat input. The average ultimate tensile strength (F), maximum displacement (L), and failure energy (E) of the welded joint produced by the moderate welding heat input are 10.27 kN, 1.88 mm, and 13.55 J, respectively, which are obviously larger than those obtained by the insufficient welding heat input (F: 8.33 kN, L: 1.20 mm, and E: 7.10 J). Although the mechanical properties of the welds achieved by the overlarge welding heat inputs present comparable levels (F: 9.73 kN, L: 1.86 mm, and E: 13.51 J), their standard deviation is much higher. Acicular ferrite, grain boundary ferrite, side plate ferrite, Widmanstätten ferrite, and pearlite are noticed in the fusion zone (FZ), while the coarse grain heat-affected zone (CGHAZ) is composed of upper and lower bainite, grain boundary ferrite, Widmanstӓtten ferrite, polygonal ferrite, and pearlite. As the welding heat input increases, the pre-austenite grain width in the FZ and CGHAZ decreases. The descending order of the microhardness distributed in the welded joints is fusion line, CGHAZ, FZ, fine grain heat-affected zone (FGHAZ), and base metal. In addition, the microhardness values of FZ and CGHAZ decline with the rise of the welding heat input. Nonetheless, no apparent links are found between the microhardness levels of the FGHAZ and welding heat input. [ABSTRACT FROM AUTHOR]

The hydro-assisted tube pressing (HATP) process is a new severe plastic deformation method that is proposed in this paper to improve the mechanical properties of long tubes. The pressured fluid between the tube and die eliminates the friction force between the tube and die and, thereby, decreases the required forming force. This facilitates the production of high-strength relatively long tubes. In the current study, this process was applied to a commercial pure copper tube during six passes at room temperature. Then, the hardness, tensile and electrical properties, and also microstructure of the samples were investigated. With increasing the number of passes, the grain size of the copper tube decreased. After two passes of the HATP process, the values of yield strength and ultimate tensile strength increased from 150 and 223 MPa to 347 and 366 MPa, respectively, and the total elongation decreased from 32 to 10%. After four passes, the tube hardness significantly increased from 81 to 132 HV, and a homogeneous distribution of hardness was obtained along with the tube thickness. The electrical conductivity of the copper tube decreased by 3% after two passes. Also, the effective plastic strain and the required processing force were investigated using the Abaqus commercial finite element software. It is concluded that the required force and the strain distribution are independent of the tube length. The hydro-assisted tube pressing method potentially can be used in the industrial production of long tubes with high mechanical strength and electrical conductivity. [ABSTRACT FROM AUTHOR]

Cross wedge rolling (CWR) has unique advantages in the production of shaft preforms with refined grains and improved mechanical properties. Considering the sensitivity of Ti-6Al-4V(TC4) alloy to heat treatment temperature, the effect of different initial deformation temperatures (IDTs) on the forming quality, mechanical properties, and microstructure evolution of the TC4 alloy lower arm preforms in CWR forming was studied in this work. The flow stress curves of TC4 alloy in the two-phase region were obtained by isothermal compression experiments. The Arrhenius constitutive model was established and applied to DEFORM-3D finite element (FE) software to simulate the CWR forming process of TC4 alloy lower arm preforms. The forming quality of TC4 alloy parts was compared and analyzed by 3D FE simulation and experiment. And their mechanical properties at room temperature were tested by tensile test. The results showed that the rolled part has well forming quality (no steps and necking defects) and higher geometric dimension accuracy at the IDT 885°C. Moreover, with the increase of IDT, the radial force and torque in the rolling process decrease. In addition, there were no internal defects in the parts rolled by different IDTs, because the die gap reduces the number of alternating cycles of tensile-compressive stress in the rolled workpieces. Compared with the initial state, the microstructure was refined. When the IDT is 885 °C, the ultimate tensile strength (UTS), yield strength (YS), and elongation (EI) of the parts were 987 MPa, 924 MPa, and 16.8%, respectively, which was able to ensure the mechanical performance requirements of the lower arm preform. The results provide theoretical guidance for the actual production of lower arm preform by CWR. [ABSTRACT FROM AUTHOR]

In this work, the effect of material location and tool deviation on global and local mechanical behavior of dissimilar AA2024/AA7075 friction stir weld joints was investigated. The results showed that increasing the tool deviation value up to 1 mm towards the soft material, fixed in the advancing side, improved the material mixing quality and enhanced the grain refinement in the stir zone. It was found that the highest ultimate tensile strength was obtained when the AA7075 alloy was fixed in the retreating side for 1-mm tool deviation towards the AA2024 alloy. Above this deviation value, a gradual decrease of the global mechanical properties of the weld joints was noticed. The digital image correlation (DIC) technique coupled to tensile testing revealed an improvement of local strain in the stir zone as well as the heat-affected zones of the dissimilar joints when the AA2024 alloy was positioned in the advancing side. [ABSTRACT FROM AUTHOR]

The effects of process parameters on microstructure and mechanical properties of the 316L stainless steel helical micro-diameter spring (316L HMDS) fabricated by selective laser melting (SLM) were explored. By optimizing SLM process parameters, the near-full density (> 99%) SLM-316L HMDS can be manufactured. The SLM-316L HMDS exhibits typical layered morphology consisting of micron-sized melt pools and columnar grains whose growth orientations are consistent with the temperature gradient. Lower hatch space reduces the formation of voids, resulting in better density, elongation, and ultimate tensile strength of the SLM-316L HMDS. The form angle significantly affects the yield strength and ultimate tensile strength, and obvious dimples appear on the fracture surface, demonstrating toughness fracture. The experimental results establish the correlation between the process parameters of SLM and the microstructure and macro-mechanical properties of the SLM-316L HMDS. [ABSTRACT FROM AUTHOR]

With increasing demand of high strength to low weight ratio materials, aluminum alloys are getting more commercial importance. Investment casting process following by directional solidification has the capability to produce cast parts with minimum or no grain boundary. These cast parts can perform even at elevated temperatures with improved mechanical properties, especially creep. Owing to these embedded capabilities, directional solidification process is preferred over conventional casting procedures for aluminum alloys. Properties of directionally solidified components highly depend on input parameters. This research aimed to develop the mathematical models for the prediction of ultimate tensile strength (UTS), percentage elongation, and hardness of directionally solidified Al-4.3% Cu alloy. A series of experiments were performed to investigate the effects of grain selector parameters including spiral thickness, spiral diameter, spiral pitch, and spiral rotations using Box-Bhenken design. For the adequacy and validity of mathematical models, analysis of variance (ANOVA) and confirmation experiments were performed, respectively. Spiral thickness was observed as most effective parameter affecting UTS, percentage elongation, and hardness followed by spiral pitch and spiral diameter. Microstructural analysis reveals that grain boundaries disappeared at low level spiral thickness and pitch and high level of spiral diameter and rotations. In comparison with base metal, percentage improvement in UTS, percentage elongation, and hardness ranging from 37.5~93.9%, 20.5~81.3%, and 37.6~85.3%, respectively, has been observed. Innovation in this research is the mathematical modeling of mechanical properties for Al-4.3% Cu alloy using directional solidification process. [ABSTRACT FROM AUTHOR]

Aluminum–copper alloys are widely employed in automobile and aerospace industries owing to their marvelous mechanical and physical attributes. But the major hindrance in their application is that these materials are more susceptible to casting defects such as porosity, hot tears, and shrinkage occurring during solidification. The said issues have a negative impact on the mechanical properties of the casted materials and thus limit their use. Squeeze casting is a promising choice for these materials that has an ability to manufacture near-net shape parts with superior surface finish and better mechanical properties. Although, the potential of this method is tested for a variety of materials, but its capability for casting AA2026 alloy is yet to be comprehensively explored which is the primary focus of this research. Three key parameters of squeeze casting process, namely squeeze pressure, die temperature, and pouring temperature are selected for investigating their influence on surface roughness, ultimate tensile strength, and hardness using response surface methodology. Experimental results are analyzed using analysis of variance to find the control factor's significance and adequacy of models. It has been found that squeeze pressure is the most influencing parameter for surface roughness whereas for ultimate tensile strength and hardness, pouring temperature is the major contributing factor. SEM analysis is carried out to reveal the micro-details of the fractured samples. In addition to finding optimal ranges of control variables (using contour plot analysis) for each response individually, a multi-response optimization has also been carried out using desirability approach. Furthermore, mathematical models are also developed and validated through confirmatory tests. The results of confirmatory runs depict that the proposed models have a high degree of prediction accuracy. [ABSTRACT FROM AUTHOR]

Inconel718 maintains excellent mechanical properties at high temperatures of 700 ℃ and has a wide range of applications in aerospace, high-performance turbines, and other fields. However, the use of improper laser process parameters makes the Inconel718 obtained by the directional energy deposition method have poor performance and defects, and there are currently fewer studies on the regulation of the mechanical properties of the preparation of Inconel718 by directed energy deposition. In this paper, the influencing regulation of laser process parameters of laser power, scanning speed, hatch spacing, layer thickness, and forming direction on the microstructure and mechanical properties of Inconel718 prepared by directional energy deposition is investigated by single-factor test method. The mechanical properties of Inconel718 obtained by directional energy deposition and forge are compared. The results show that, among the five laser process parameters, the laser power and forming direction have significant effect on the mechanical properties of Inconel718 obtained by directional energy deposition, while the scanning speed, scanning spacing, and layer thickness have less influence on its mechanical properties. Compared with Inconel718 prepared by ordinary forge, the tensile strength of Inconel718 obtained by directed energy deposition is reduced by 7.64%, the hardness is increased by 23.55%, the impact strength is reduced by 17.6%, and the plasticity is reduced obviously. Good mechanical properties can be reached from the Inconel718 obtained by the directional energy deposition method. [ABSTRACT FROM AUTHOR]

By using N-methyl-2-pyrolidone (NMP) and tetrahydrofuran (THF) solvents, the yield of two-dimensional material graphene as carried out via a technique called liquid exfoliation, phases including dispersal of preponderant material (graphite), sonicating the elevated surface tension solvents and decontamination for the eradication of impurities and remnant were implied in this yield. Now, these progressions were implemented by the use of bath Sonicator, ultracentrifuge, and probe Sonicator. Few-layer graphene (FLG) was originated which fused into intricate architecture (polymer matrix) in order to yield nano-composites of polystyrene and graphene via the technique of solution forming at contrasting filler loadings. The study of the upshot of graphene nano-filler, at divergent wt% ages of graphene’s exfoliation at scanty percolation, i.e., (EG) (i = 0, 0.1, 0.3, 0.5, 0.7, 0.9) on mechanical, microstructural, thermal, and electrical properties of polystyrene matrix, was carried out. This was done with the help of atomic force microscopy (AFM), four-probe method, X-ray diffraction (XRD), scanning electron microscopy (SEM), and universal testing machine (UTM). The 1-μm occurrence of two-dimensional sheets of graphene was marked by the SEM outcomes, whereas the composite system that contains polystyrene crests and graphene planes was ascertained via XRD testing. The 0.757-nm thickness which clearly specified the two-dimensional sheets was reckoned by AFM. The maximum increase, in mechanical properties including ultimate tensile strength (UTS), modulus of elasticity (E), and percentage elongation at break point, was 74.75, 150, and 68.65% respectively as related to the pure sample of polystyrene that was accounted in this research at scanty percolation (EG = 0.9 wt%). These properties are the function of filler loading. Electrical conductivity and electrical resistivity were evaluated; an intensification of 121.26% at 0.9% in electrical conductivity of filler loading as related to pure polystyrene was accounted whereas the electrical resistivity was diminished up to 121.19% at the identical filler loading. The ultimate increase in the thermal conductivity was 123.71% at concentration 0.9 wt% of the filler as confirmed by thermal conductivity outcomes. The better dispersion of the filler in the matrix and higher interfacial contact between the filler and polymer create these increasing trends. [ABSTRACT FROM AUTHOR]

Synthesis of few layered graphene (FLG) was done by liquid exfoliation method using N-methyl-2-pyrrolidone (NMP) and tetrahydrofuran (THF) solvents. Prepared samples of polystyrene matrix at different wt% ages of exfoliated graphene at low percolation, i.e., exfoliated graphene (EG) (i = 0, 0.1, 0.3, 0.5, 0.7) were characterized using scanning electron microscopy (SEM), atomic force microscopy (AFM), and X-ray diffraction (XRD) and mechanical properties which are ultimate tensile strength (UTS), modulus of elasticity (E), and percentage elongation were calculated by universal testing machine (UTM). SEM results witnessed presence of 2D sheets of graphene sheets while XRD identified polystyrene peaks and graphene planes in composite system. AFM clearly quantified the thickness of graphene sheets would be 0.757 nm. Increase in UTS, E, and percentage elongation at break is a function of filler loading and maximum increase in those properties is 52.66, 462.28, and 112.5% as compared to those of pure polystyrene sample that was recorded in this experimentation. This increasing trend of properties depends upon high interfacial contact between filler and polymer and better dispersion of filler in matrix. By increasing the wt% age, filler leads to agglomeration of sheets which tend to decrease in percentage elongation as obtained at concentration of EG = 0.5 wt% in samples. [ABSTRACT FROM AUTHOR]

This study aims to explore the Bauschinger effect and mechanical properties of 5754 aluminum alloy and their relationship through parts manufactured by incremental forming technology. Pyramidal parts with five different wall angles were formed using incremental forming after which tensile samples from each of the parts were prepared and tested. The experimental results indicated that the Bauschinger effect existed during incremental forming of the aluminum alloy. It was also found that the level of the Bauschinger effect, yield strength, and ultimate tensile strength increased with the expanding wall angle. Compared with the influence of the Bauschinger effect, the work hardening plays a leading role in the change of mechanical properties. Based on the study results, the formulas for predicting the mechanical properties at different wall angles are obtained. Understanding the Bauschinger effect and mechanical properties can help to guide incremental forming simulation and process development of parts manufactured by incremental forming. [ABSTRACT FROM AUTHOR]

In the present work, feasibility study on dissimilar friction stir welding (FSW) of immiscible materials of St37 and Al 2024 is fully investigated. Towards that end, three tool rotational speeds of 224, 355, and 450 rpm along with three traverse speeds of 20, 25, and 31.5 mm/min were employed to achieve optimum FSW parameters. Besides, effects of process parameters on microhardness and tensile properties of the joints were studied as well. Optical microscopy (OM), scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS) were also executed to investigate the microstructure and the brittle intermetallic compounds (IMCs) within the stir zone (SZ) which revealed the presence of FeAl IMCs within this region. Lowering the rotational speed led to further diminution of IMCs and resulted in superior mechanical properties. Increasing the rotational speed raised the microhardness values of the SZ due to the grains refinement and increase of the IMCs. Additionally, increasing the traverse speed raised the ultimate tensile strength of the joints due to the reduction of IMCs and also the annealing effect of the heat input. The highest ultimate tensile strength of 331.5 MPa was obtained at rotational and traverse speeds of 224 rpm and 31.5 mm/min, respectively. [ABSTRACT FROM AUTHOR]

Niobium is an important material for high temperature applications, in space, in superconductors or in chemical process constructions. Laser-based powder bed fusion of niobium (PBF-LB/M/Nb) offers new opportunities in design, though it is still an expensive technique. The build-up rate is an important factor for economical manufacturing using PBF-LB/M/Nb. It is largely influenced by variation of process parameters, affecting the heat flow during the manufacturing process. In this work, an empirical model for PBF-LB/M/Nb is developed. Based on this model, manufacturing parameter sets using different volume build-up rates are predicted and confirmed. They enable the manufacture of parts with homogeneous and crack-free microstructure with more than 99.9% relative density. Tensile and hardness tests of specimens, which were manufactured using different parameter sets, are performed to determine the effects of the build-up rate—and thus the heat flow during manufacturing—on different mechanical properties. The ultimate tensile strength and yield strength of as-manufactured specimens reach values up to 525 MPa and 324 MPa, respectively, while the elongation at break ranges between approximately 8 and 16%. The Vickers hardness of all specimens was in the range of 149 ± 8 HV0.1. In addition, the microstructure of the manufactured samples is investigated by means of light as well as scanning electron microscopy. [ABSTRACT FROM AUTHOR]

Metal powder hot embossing (MPHE) is a low-cost micromanufacturing technique that can produce metallic parts with aspects in micron scale. In this study, scanning electron microscopy (SEM) is employed for evaluating the shape retention and the homogeneity of microstructure of replicated geometries into AISI 316L powder feedstock by the secondary electron imaging (SEI) and the backscattered electron imaging modes, the distribution of chemical composition by the electron-dispersive spectroscopy (EDS) mapping, and grain structures by the electron backscatter diffraction technique. Moreover, the SEI and EDS techniques completed the failure analysis of tensile tests. Nanoindentations were also performed to assist phase identification analysis in the densified microstructure. Different geometries in the micron scale (micro wall half-reservoirs, micro channel half-flanges, convex and concave micro gear configurations, and micro tensile specimens) were selected for replication. Shaping limitations were attributed to the geometry, convex or concave, and the stiffness of the die. Micro gear and micro wall configurations were shaped using a stiffer elastomer (T = 230 °C and P = 11.3 to 14 MPa for 45 min) and a metallic die (T = 170 °C and P = 11.3 MPa for 10 min), respectively. The shaping of concave geometries was achieved regardless of the metal powder concentration, 60 and 65 vol.%. Densified parts retained the replicated micro configurations after long periods of thermal debinding and sintering, with densification above 95%. The chemical composition in sintered parts was homogeneous. The microstructure was principally composed of austenitic grains. The 316L stainless steel sintered part produced through MPHE presented an ultimate tensile strength of 458 ± 15 MPa, similar to that of a wrought AISI 316L alloy; the fracture type in the micro tensile specimen was ductile. [ABSTRACT FROM AUTHOR]

The success of laser-foil-printing (LFP) additive manufacturing depends critically on the laser welding of sheet metals onto the substrate or the previous layer during the part fabrication process. The welding can be generally categorized into two modes: conduction mode and keyhole mode. In this study, 304L stainless steel parts fabricated by the LFP process using the two laser welding modes are compared. The porosity, microstructure, and tensile properties of the fabricated parts in these two modes are measured and compared in the laser scanning direction (X) and part building direction (Z). The parts fabricated in the conduction mode have a higher density than those fabricated in the keyhole mode. On the tensile properties, both yield strength (YS) and ultimate tensile strength (UTS) have insignificant differences statistically based on the ANOVA analysis between the tensile specimens fabricated with the two welding modes by the LFP process. However, the conduction-mode parts have higher elongation than the keyhole-mode parts in both the X and Z directions, and the difference is especially significant in the Z direction. By using the electron backscattered diffraction (EBSD), it was found that the much higher ductility for the conduction-mode parts in the Z-axis direction is mainly due to the distinct grain boundary interface density in the Z-axis direction between the two welding modes. [ABSTRACT FROM AUTHOR]

Cylindrical parts with inner ribs (CPIR) of magnesium alloy have increasingly become a research focus to adapt the continuous improvement of lightweight requirement. The hot power spinning (HPS) method was proposed to form the magnesium alloy CPIR, and the microstructures, textures, and mechanical properties of blank and spun workpiece at cylindrical wall (CW) and inner rib (IR) were analyzed experimentally. The results show that the average grain size at CW and IR of spun workpiece is refined from 2.49 μm of blank to 1.88 μm and 2.11 μm, respectively. The c-axis of most grains at CW and IR of spun workpiece is deflected from tangential direction (TD) to radial direction (RD) by 90° and 72°, respectively. Compared with blank, the elongation at CW and IR of spun workpiece is increased by 52.2% and 39.8%, respectively. The yield strength and ultimate tensile strength of IR are basically the same as those of blank, while those of CW are decreased by 6.5% and 3.9%, respectively. The difference of macro fracture directions of tensile specimen of blank and spun workpiece is resulted from the change of grains c-axis direction and the increase of grain freedom degree around c-axis. [ABSTRACT FROM AUTHOR]

The structure and properties of cold-rolled strips with a thickness of 3 mm from an experimental aluminum alloy 1580 with a lower scandium content of 0.03% (wt.) relative to the grade of the aluminum alloy and a 5083 similar alloy without scandium were studied. Ingots obtained at the laboratory installation of semicontinuous casting of the foundry department of the Siberian Federal University (Siberian Federal University, Russia, Krasnoyarsk) were used. The preparation of ingots for rolling included milling up to sizes of 40 × 100 × 145 mm and annealing according to a two-stage mode: at a temperature of 350 °C for 3 h (first stage) and at a temperature of 425 °C for 4 h (second stage). Hot rolling was carried out in the laboratory of the Department of Metal Forming at the Siberian Federal University at a temperature of 450 °C on a two-roll hot rolling mill with a roll diameter of 330 mm and a barrel length of 520 mm to a thickness of 5 mm, which corresponded to a total reduction of 88% with a single reduction of 2–5%. For cold rolling, a two-roll sheet rolling mill with a roll diameter of 200 mm and a barrel length of 400 mm grade LS 400 AUTO was used. Rolling was carried out to a thickness of 3 mm with a single reduction of 2–5%, and then the strip was annealed. The results of determining the mechanical properties by tension by the universal LFM400 machine showed that with an increase in the annealing temperature in the range from 250 to 350 °C for 3 h, ultimate tensile strength of the cold-rolled strips of aluminum alloy 1580 decreases from 385 to 365 MPa. For aluminum alloy 5083, a decrease in this strength characteristic is also observed from 345 to 320 MPa. A decreasing tendency with increasing annealing temperature was also observed for the conditional yield strength Rp, and over the entire range of annealing temperatures, the values ​​of Rp for strips of alloy 1580 were higher than for alloy 5083 by 35–40 MPa, which amounted to 14–17% The values ​​of the plastic properties, for which the value of the elongation to failure was analyzed, were close throughout the range of annealing temperatures for both alloys. The results of the analysis of micro- and fine structure allowed to conclude that an increase in the strength properties of cold-rolled and annealed sheets from the experimental alloy 1580, compared with alloy 5083, is a consequence of the addition of scandium in the experimental alloy 1580, which leads to an increase in the temperature of recrystallization of the alloy, preserving it contains a subgrain structure and dispersion hardening caused by precipitation of Al3(Sc, Zr) phase particles during the decomposition of a solid solution. [ABSTRACT FROM AUTHOR]

Ecological impact of improper disposal of growing agricultural waste is huge. These low cost, renewable, and biodegradable materials can be utilized in production of eco-friendly polymer composite. However, further property enhancement can be achieved by hybridization. This work evaluated the feasibility of enhancing the properties of Bambara nut shell particulate (BNSp) reinforced polyester composite by incorporation of clay. Ultimate tensile strength (UTS) of 23.98 MPa was recorded for the hybrid composite of 3 wt% clay + 12 wt% BNSp compared to 19.86 MPa for 12wt% BNSp polymer composite. DMA analysis showed a damping factor of 0.586 at 89.51 °C for 3 wt% clay + 12 wt% BNSp composite. Clay addition modifies and improves the properties of agro-waste reinforced polymer composites with clay/BNSp/polyester composite exhibiting higher mechanical properties compared to the BNSp reinforced polyester composite due to the ability of the clay to insert themselves between the layers of the polyester matrix. This work also showed that Bambara nut is a potential low-cost filler material for polymer composites and can be used in areas requiring medium strength but lightweight materials. [ABSTRACT FROM AUTHOR]

Squeeze overcasting has emerged as an attractive option for casting of Al alloys in terms of mechanical properties. The attainment of the desired magnitude of these properties is challenging in overcasting due to the involvement of a number of process parameters. In this study, the effects of insert preheat temperature (TI) along with pouring temperature (TP), and squeeze pressure (PS) on the mechanical properties of squeeze overcast AA2026-AA2026 joint were investigated. Experimental results revealed that the squeeze pressure is the most prominent factor affecting the ultimate tensile strength (UTS) while micro-hardness (MH) is significantly influenced by the pouring temperature. Maximum values of UTS (315 MPa) and MH (130 HV) were achieved at a PS of 120 MPa, TP of 780 °C, and TI of 250 °C. Energy dispersive X-ray (EDX) analysis witnessed that TI has also a significant role in determining the quality of bond between the substrate and the melt. Scanning electron microscopy (SEM) depicts that the morphology of the fractured surface has a sound influence on both selected responses. Both the strength and hardness are noticed better if the fractured surface possesses the flat-faced morphology. Furthermore, an empirical regression model was developed using response surface methodology (RSM) design and validated through eight confirmatory experiments. RSM integrated multi-objective optimization genetic algorithm (MO-GA) was deployed to optimize the UTS and MH. The comparative results obtained from RSM and MO-GA demonstrated that the deviation in experimental and predicted values is less than 5%. [ABSTRACT FROM AUTHOR]

Metal 3D printing has gained a lot of attention among industries since it offers a practical solution to problems rising during the manufacturing of parts and components with complex geometry. This is an additive technology that eliminated several fabrication steps and at the same time reduces material waste during the manufacturing process. However, in all additive manufacturing technologies, the final properties of the parts are determined by the operational process parameters. In this study, several machine learning algorithms were examined to characterize the effects of the printing process parameters on relative density, hardness, yield strength, and tensile strength in manufactured parts. It was possible by using "Big Data" collected from a large number of previously published articles on the application of laser powder bed fusion (LPBF) for the 3D printing of 316L stainless steel samples. Among different process parameters, laser power, laser energy density, and scanning speed were proven to have the largest effects directly on the physical and mechanical properties of LPBF-processed parts. Six different classification models and five support vector machine regression-based models were tested to find the most accurate prediction algorithm. To validate the obtained results from the applied machine learning models, a set of 316L specimens were produced using LPBF technology using a random set of process parameters. The physical and mechanical properties of 3D printed samples were tested and compared to the ones predicted from the optimum models from machine learning analysis. The results were in great agreement, which shows the high accuracy of the developed machine learning algorithms in this study. [ABSTRACT FROM AUTHOR]

This paper deals with the direct recycling of EN AW 2011 aluminum alloy turning chips into semiproducts utilizing forward hot extrusion process. The main goal of this study is to obtain mathematical models that will relate the process parameters of direct recycling to mechanical properties of final semiproducts. Influence of chip size, compaction force, and extrusion temperature on mechanical properties was investigated using Box-Behnken experimental design. The study has shown that the most influential factor on mechanical properties was extrusion temperature. Chip size does not affect both ultimate tensile strength and yield strength and on the other hand, compaction force does not influence on both ultimate tensile strength and percent elongation. Optical microscopy revealed cracks and inhomogeneities for all samples extruded on 300 °C in contrast to those extruded on 500 °C which showed no voids or cracks. Optimal recycling process parameters that would give maximal mechanical properties were found. [ABSTRACT FROM AUTHOR]

The isothermal forging of a cast Mg-5.89 wt.% Zn-0.79 wt.% Y-0.32 wt.% Zr magnesium alloy was carried out to form the tank cover. The forming process of isothermal forming is studied by finite element model simulation and experiment. Based on the optimum isothermal forging process, the isothermal forging experiments of the cast Mg-Zn-Y-Zr magnesium alloy tank cover were successfully conducted. The results show that the experimental results such as forming load are in good agreement with the calculated ones. The tank cover forging with complete die fill and without fold defect can be obtained by utilizing the optimum isothermal forging process. The mechanical properties of the tank cover show a significant improvement over those of original materials, and the tank cover exhibits an ultimate tensile strength of 302 MPa, a yield strength of 209 MPa, and an elongation of 13%. [ABSTRACT FROM AUTHOR]

The present study has investigated the influence of calcium process control agent on the microstructure and mechanical properties of powder metallurgy processed samples fabricated by milling and spark plasma sintering technique. The microstructure of spark plasma sintered Ti-6Al-4V with 0.3 wt% Ca (Ti-6Al-4V-0.3Ca-M) samples revealed fine grain structure compared to sintered unmilled (Ti-6Al-4V-UM) samples. The average grain size values of sintered Ti-6Al-4V-0.3Ca-M and Ti-6Al-4V-UM samples are 8 and 60 μm, respectively. The spark plasma sintered Ti-6Al-4V-UM exhibited a yield strength (YS) of 875 ± 10 MPa, ultimate tensile strength (UTS) of 1057 ± 2 MPa, and % elongation (% El) of 15 ± 2. The spark plasma sintered Ti-6Al-4V-0.3Ca-M exhibited higher YS of 964 ± 9 MPa, UTS of 1153 ± 7 MPa, and lower % El of 6 ± 1 when compared to mill annealed Ti-6Al-4V alloy (YS 899 MPa, UTS 978 MPa and %El 15). The higher strength of Ti-6Al-4V-0.3Ca-M sintered samples could be attributed to the fine grain structure and the presence of interstitial elements in the matrix. In contrast, the lower strength of Ti-6Al-4V-UM can be ascribed to its coarse grains. [ABSTRACT FROM AUTHOR]

A series of experiments of high-power fiber laser-arc hybrid welding of pure copper was carried out. It could be seen that the microstructure of weld metal was obviously coarsened, and the columnar grain spacing at fusion zone and the massive grain size at heat-affected zone were both linearly increased with the increase of heat input. The weld conductivity decreased with the increase of heat input because the widening weld increased the microstructure nonuniformity of test samples. The heat input as well as welding parameter has no obvious effect on the ultimate tensile strength (UTS) of cross-weld but has obvious effect on the elongation. The UTS of all the welds was 200 MPa or so. The elongation was bigger than 20% when the heat input was in the optimization range from 250 to 380 J/cm. The decrease of the elongation was attributed to either high porosity at insufficient heat input or coarser grain at excessive heat input. [ABSTRACT FROM AUTHOR]