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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]

In this paper, a disk laser welding was developed to join 3-mm thin-Sect. 30Cr3 ultra-high-strength steel which was widely used in aerospace. The microstructure and mechanical properties of welded joint were investigated in detail. The results indicated that the recommended laser linear energy range were between 150 and 165 J/mm to guarantee that the melting width was up to 1 mm as well as less oxidation, spatter, and depression on the weld. Meanwhile, for the as-welded (AW) condition, the base metal (BM) consisted of ferrite matrix with distributing small spherical carbides, also known as spherical pearlite. While, the fine grained region, coarse grained region, and weld metal were all composed of martensite. However, the partially transformed region mainly consisted martensite with a little of spherical pearlite. Meanwhile, the average grain sizes of weld metal, HAZ, and base metal were 1.3 μm, 1.5 μm, and 1.8 μm, respectively. However, for the post-weld heat treatment (PWHT) condition, the whole welded joint was all composed of tempered martensite, and the average grain size of welded joint was about 1.7 μm. The tensile strength of the welded joint was higher than that of the base metal both in the AW and PWHT condition as all the fracture with shrinkage occurred in the BM of the specimens. Additionally, the average yield strength of the AW and PWHT are about 600 MPa and 1700 MPa, respectively. [ABSTRACT FROM AUTHOR]

Titanium alloy extruded profiles with complex cross-section are usually used to manufacture special-shaped structural parts in the aviation industry. In this paper, a Ti-6Al-4 V profile with asymmetric Y shape was manufactured by a direct extrusion process. A comparative study was conducted at the different lubrication conditions, in which the different process deformation mechanisms, resulting microstructures, and mechanical properties of profiles have been investigated by finite element simulation and a series of experiments, i.e., scanning electron microscope (SEM) and electron backscatter diffraction (EBSD). It was revealed that the metal flow is blocked at the narrow die orifice due to the deterioration of lubrication, resulting in the continuous shrinkage defect. The metal deformation coordination mechanism becomes gradually significant due to poor friction contact, which promotes the internal stress in the cross-sectional center to transfer outward to balance the friction at the edge of the orifice, resulting in the reduction of the effective strain in the center. The heat generated by friction weakens the heat exchange behavior between the metal and the die, which helps the profile retain a more uniform temperature field. In the sectional center of the profiles made from the two different lubrications, extrusion with good lubrication results in greater grain/colony refinement due to greater effective strains, and a slightly greater dislocation density was found due to the uniform deformation. The tensile tests revealed that compared with poor lubrication, due to the improvement of Hall–Petch strengthening and dislocation strengthening in the cross-sectional center with good lubrication, the variation range of yield strength and tensile strength is reduced to 11 MPa and 7 MPa, respectively, and the variation range of microhardness is reduced to 44 HV and 32 HV, respectively. The improvement of lubrication not only helps to reduce forming defects but also can obtain uniform mechanical properties. [ABSTRACT FROM AUTHOR]

The spread of 3D printing in many different fields has become eminent. This paper aims to improve the mechanical properties of parts printed by fused deposition modeling technique. Acrylonitrile butadiene styrene (ABS) specimens are printed with custom printing parameters. These parameters give a tensile strength that is 86% of the injection- molded ABS strength, and give one of the best recorded results for 100% infill printed ABS tensile specimens. Furthermore, a post filling technique has been studied. Specimens are printed with inner voids and different densities using slicing software. Void shape is precisely selected to conform to the filling process. High-strength, low-cost thermoset resin is injected through specimens to fill those voids. A tensile test has been performed after the full curing of the resin. A morphology analysis is done. Using this technique strength to printed weight ratio is improved by 151% and the cost is reduced by 51%. [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]

The most advanced metal 3D printing promises to revolutionize the manufacturing industry and has already played their strengths in the field of part repair and surface coating, but they have not yet reached the best operability in the overall manufacturing. The challenge is how to design the process route. Therefore, the entire process of blade design-manufacture-testing was carried out in this paper. The fifth-degree polynomial is used to construct the blade, and on this basis, a CAD model of a thin-walled blade with torsion was established. After the blade was manufactured by LMD, the geometric dimensions and mechanical properties were tested. The test results show that the standard deviation of the blade body part is less than 0.3 mm, which basically meets the design requirements. The Vickers hardness of LDM blades changes continuously along the deposition direction, mainly due to the changes in the structure caused by different cooling rates. The tensile strength of the blade is basically the same in the 0°, 45°, and 90° directions, which is greater than 770 MPa. The elongation in different directions differs more than 5% and has obvious anisotropy, which is mainly caused by the organization structure and the way of unit cell stacking. [ABSTRACT FROM AUTHOR]

Submerged friction stir welding on magnesium (Mg) alloy is investigated with limits in the past. ME20M is an important lightweight Mg alloy with enhanced yield strength and heat resistance that merits further research. In this paper, submerged friction stir welding of ME20M Mg alloy was carried out in different temperatures of cooling water. Three-dimensional numerical was employed to analyze the thermal field under the same weld conditions, and the numerical predictions were compared with the experimental results. The macrostructure, microstructure, tensile properties, and hardness are tested. The results show that the numerical results and the experimental results exhibits the same trends. By increasing the cooling water temperature, the grain size of the weld nugget increased, the tensile strength of the joint decreased, and the microhardness of the weld joint decreased. The largest tensile strength was 170.5 MPa, which was ~ 71.04% of the base metal. The highest and the lowest hardness values of the weld joint were obtained at the cooling water temperature of 15 °C and 75 °C, respectively, in the weld nugget and heat-affected zones. [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]

The present paper aims to study different laser drilling/cutting parameters including laser intensity, cutting speed, and gas pressure in order to achieve minimum surface roughness (Ra), heat-affected zone (HAZ), taper angle (TA), and maximum tensile strength (TS) of the laser-drilled glass fiber-reinforced plastic (GFRP) laminate. Full factorial design of experiment method and analysis of variance were adopted to investigate the effect of each parameter on the responses, and in addition, the surface roughness and tensile strength were compared with that of conventional drilling. The morphology of the laser-drilled holes was studied through the scanning electron microscopy (SEM). It was found that optimum laser drilling parameters can yield higher tensile strength and lower surface roughness in drilled GFRP laminate compared to the conventional drilling. Moreover, multi-response optimization was carried out on the results in order to obtain maximum tensile strength, minimum HAZ, minimum surface roughness, and minimum taper angle. The results revealed that the laser intensity, cutting speed, and assist gas pressure should be set at 2.04 W/cm2, 8 mm/s, and 4 bar, respectively, to obtain higher tensile strength and surface integrity. The results drawn from this study can be applied to improve the surface quality and mechanical properties of laser drilling of FRP materials especially in aircraft part manufacturing. [ABSTRACT FROM AUTHOR]

Additive manufacturing (AM) has various independent parameters that affect the mechanical properties and quality of the produced parts that are not linearly the function of each other. Process parameters in metal AM are very hard to control, analyse and optimise because they affect each other even though they can be independently changed. Changing process parameters in a wide range is not possible due to the formation of problems such as cracks, balling, unmelted powders, porosity and distortion. In this paper, a numerical model to predict the value of tensile strength of selective laser melting (SLM) Ti-6Al-4V parts and analyse the effect of process parameters on the results has been proposed. Taguchi L25 Design of Experiment (DOE) across 125 samples to create a comprehensive and general overview of influential parameters on the build process was investigated. Specifically, parameters included laser power, scan speed, hatch spacing, laser pattern angle and heat treatment (HT). To evaluate and analyse the build process according to established statistical variances, a minimum of five samples based on ASTM standard (for tensile test) were prepared. Heat treatment was added to the DOE to analyse the combined process and post-process effects. Results were compared (cross-validated) against existing values found in the literature and were found to effectively predict and explain the behaviour of tensile strength when changing process parameters. [ABSTRACT FROM AUTHOR]

The aim of this study is to evaluate the effect of printing parameters and their interactions on the mechanical properties of ABS-based specimen, 3D printed by fused deposition modeling (FDM), using the response surface method. The manufacturing direction (X, Y, or Z) and the deposition angle (0°, 30°, or 45°) are analyzed as input factors. The Young modulus, the yield stress, the tensile strength, and the deformation at fracture in tension are considered as responses. An empirical model for each response is built in terms of factors and their interactions. The predicted results are in good coherence with experimental ones. The original contribution of this paper consists in the evaluation of the optimal combination of manufacturing parameters thanks to the MINITAB software. [ABSTRACT FROM AUTHOR]

Additive manufacturing (AM) started as a rapid prototyping (RP) technology to aid in visualizing and validating designs in the design process. However, with the recent improvements in metal AM parts, functional parts can be manufactured using laser-based AM. Currently, metal AM parts have comparable mechanical properties to traditional manufacturing parts. 15-5PH stainless steel and Inconel 718 are two of the most commonly used metals in laser-based AM, and they have a high modulus of elasticity and tensile strength and can be precipitate hardened to increase their strength and hardness by heat treatment. These properties make 15-5PH stainless steel and Inconel 718 suitable for many industrial applications such as aerospace and automotive. However, due to the nature of AM, AM parts usually suffer from anisotropy. In this paper, the mechanical properties such as tensile strength, modulus of elasticity, yield strength, and ductility are investigated at various elevated temperatures up to 350 °C and compared with the mechanical properties at room temperature using specimens printed in three different orientations to capture the effect on the anisotropy. In addition to that, the microstructure of the specimens is studied to investigate the influence of elevated temperature on the specimens. [ABSTRACT FROM AUTHOR]

Incremental sheet forming (ISF) is a promising method for forming metal sheets, by which parts can be manufactured without the use of dedicated dies. However, the process has not been widely used for industrial application due to the unsatisfactory service performance of the formed parts. This paper focuses on improving the thickness distribution and mechanical properties (e.g., hardness, yield strength, and tensile strength) through process optimization. The response surface methodology with a Box-Behnken design is used to investigate how different process parameters affect the thickness thinning and mechanical properties. A set of experiments with 15 tests for pyramid-forming process is performed, and three parameters including step-down size, sheet thickness, and tool diameter are considered. The results show that the maximum thinning rate is lower with larger step-down size and larger tools. In addition, compared with the initial sheet, the values of hardness, yield strength, and tensile strength have been increased considerably due to the strain hardening. The present work provides useful guidance in improving the product quality formed by incremental sheet forming. [ABSTRACT FROM AUTHOR]

In this paper, the effect of additive particles on the mechanical properties of ultraviolet (UV)-cured resin was evaluated based on tensile strength and shear strength. The experimental results showed that the tensile strength was improved with proper particle addition, but the shear strength was always decreased. Moreover, the effects of additive particles on the holding force of diamond abrasive, critical exposure energy, and penetration depth of UV-cured resin were elucidated. The holding force of resin with 15 wt.% Al2O3 addition was found to be higher than that of pure UV resin. Based on the experimentally determined critical UV exposure energy and penetration depth, UV-cured resins with and without additive particles were used to fabricate grinding wheels using additive manufacturing technology. Grinding experiment demonstrated the performance of UV resinoid grinding wheels was significantly improved with the addition of 15 wt.% Al2O3 particles. [ABSTRACT FROM AUTHOR]

The forming temperature of cross-wedge rolling (CWR) usually ranges from 950 to 1150 °C, but reducing the forming temperature has some advantages. This paper presents a comprehensive study of warm and hot cross-wedge rolling by using high-strength bolts as a case. Numerical simulation and experimental trials were conducted to make a detailed comparison of warm and hot cross-wedge rolling. Forming quality, microstructure, and mechanical properties of the rolled rods were investigated using scanning electron microscopy (SEM) and tensile testing. The results show that the rolling force and torque of warm cross-wedge rolling (WCWR) are more than three times greater than those of hot cross-wedge rolling (HCWR), and the workpiece rolled by WCWR shows more pit and stacking defects but fewer central cavities. The dispersing spheroidized cementite on ferrite matrix generated in WCWR results in decreased hardness and tensile strength of the rolled rods and a significant increase of elongation, which improves subsequent machinability. [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]

Weld line problem which occurs in polymer parts produced by plastic injection method and affects appearance and strength on a large scale was researched in this paper. The three parameters affecting operation were called injection pressure, injection time, and packing pressure which influence the quality of weld line on the polymer products were researched. A joint which enables two different parts used in different places to be joined together and its subjection to a certain loan were discussed. Considering the usage area of the part, composite of glass fiber reinforced polyamide (PA 6 GFR 30) was chosen as the material, and the design process of the part was implemented. Samples were prepared by altering the determined injection parameters. Weld line of the produced samples were subjected to tensile strength test. Their structure parts were examined under the SEM, and the results were gathered. [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]

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]

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 article investigated the effects of friction stir additive manufacturing (FSAM) process parameters on the microstructure and mechanical properties of copper. The FSAM tool plunge depth, tilt angle, and rotational and traverse velocities are considered as variables. Material flow, internal defects, hardness, and mechanical properties are analyzed on FSAM samples. The results show that the FSAM of copper is very sensitive to process parameters, and incomplete deposition can happen during FASM with inappropriate process parameters. The microstructure of the printed layer tolerates a thermo-mechanical cycle during the process and reheating after depositing new layers. In the center of the print, an ultra-fine grained zone formed called the re-stirring area. The highest strength printed sample achieved at 3° degree tool tilt, 0.25-mm plunge depth, 2000-rpm rotation, and 16-mm/min traverse speed that has ~85-HV hardness and 205-MPa tensile strength. [ABSTRACT FROM AUTHOR]

In this study, a numerical model was developed using the Smoothed Particle Hydrodynamics (SPH) method in ANSYS-Autodyn-2D to investigate the bonding phenomenon of the AZ31B-Al5052 explosive joint. The experimental bonding interface shows straight and wavy structures consistent with the simulation. X-ray diffraction (XRD) detected the development of an intermetallic (Al12Mg17) compound at the interface. Due to substantial plastic deformation, the microhardness of post-weld AZ31B (92 HV) and Al 5052 (85 HV) close to the interface was increased by 21% and 25%, respectively. The shear strength (111 MPa) and ram tensile strength (173 MPa) of the AZ31B-Al5052 weld were greater than the weaker parent alloy. The pressure, velocity, and temperature developed during the AZ31B-Al5052 explosive welding were determined by simulation and correlated with the empirical relations. [ABSTRACT FROM AUTHOR]

This experimental study investigates the effects of process parameters for 3D printing polylactic acid (PLA) samples on both the mechanical properties obtained and the energy consumption in the fused deposition modelling (FDM) process. The explained experimental activities provide an in-depth evaluation of all the strategies adopted in different temperatures and scan speed strategies. The results, extracted in tensile strength, ultrasonic inspection (UT), and specific energy consumption (SEC), highlight the printing parameters that mainly affect the mechanical characteristics of the final workpieces and the energy consumption to find an appropriate energy-saving energy strategy for the PLA additive manufacturing process. The results indicate a more excellent uniformity of the molded material, reducing the printing time and total energy consumption at high speeds (V = 110 mm/s) and one level of temperature (T = 215 °C). A new efficiency index has been introduced to release guidelines to pursue the best setup compromise. [ABSTRACT FROM AUTHOR]

Austenitic stainless steel was subjected to multiple laser peening (LP) with high coverages and the gradient structures and corresponding mechanical behaviors were investigated in detail. Body-centered cubic α′ phase and hexagonal-close packed ε phase martensite induced by peening deformation accumulate in multiple LPed 304 austenitic stainless steel surface layer with the increasing coverage. In samples with 240 layers multiple LP, high density martensite in block and twins can be observed. The EBSD results show that the γ → ε → α′ martensitic transformation can be noticed to occur in grain boundaries and twins. Martensitic transformation volume fraction, twin volume fraction and hardness of multiple LPed 304 SS exhibit gradient characteristic from the top surface to substrate. The hardness of the specimens increased with the peening coverage near the top layers, and the influence of laser peening on hardness gradually vanished until 2 mm in depth, the tensile strength increased while the tensile elongation decreased, resulting from a peak power density of 8.19 GW/cm2. Multiple laser peening can be utilized as a solution to modify the mechanical performances by tailoring the gradient structure. Among the investigating range, the optimal multiple LP layers is suggested as 80 where both a relative high strength and ductility can be obtained. [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]

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]

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]

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]

Additive manufacturing (AM) is becoming increasingly popular since it offers flexibility to produce complex designs with less tooling and minimum material at shorter lead times. Wire arc additive manufacturing (WAAM) is a variant of additive manufacturing which allows economical production of large-scale and high-density parts. The WAAM process has been studied extensively on different steels; however, the influence of process parameters, specifically wire feed speed (WFS), travel speed (TS), and their ratio on bead geometry, microstructure, and mechanical properties, are yet to be studied. The present work aims at closing this gap by using the WAAM process with robotic cold metal transfer (CMT) technology to manufacture high-strength structural steel parts. For that purpose, single-bead welds were produced from HSLA steel by varying WFS between 5 and 10 m/min and the WFS to TS ratio between 10 and 20. Those variations produce heat inputs in the range of 266–619 J/mm. The results have shown that the wire feed speed to travel speed ratio is the major parameter to control the heat input. Increasing heat input increases characteristic bead dimension, whereas it reduces the hardness. In the second part of experiments, two single-bead walls were deposited via the parallel deposition strategy and one multiple-bead wall was produced using the oscillation strategy. The tensile properties were tested along two directions: parallel and perpendicular to deposition directions. For the yield strength and tensile strength, the difference between horizontally and vertically tested specimens was smaller than the standard deviations. On the other hand, the total and uniform elongation values exhibit up to 10% difference in the test direction, indicating anisotropy in ductility. Those tensile properties were attributed to repeated thermal cycles during the WAMM process, which can cause heat transfer in multiple directions. The yield strength of the multiple-bead wall produced via oscillation was lower, whereas its ductility was higher. The tensile properties and hardness differences were found to correlate well with the microstructure. [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]

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]

Active-passive filling friction stir repairing (A-PFFSR) was employed to eliminate the casting defects in the ZL210 aluminum alloys. Based on a six-spiral-grooves pinless tool, effects of rotating velocity on microstructures and mechanical properties of the repaired joints were investigated. The casting defects were firstly drilled into taper holes by a tool with a threaded pin, and then the keyhole defect was successfully filled with the materials surrounding the keyhole and an extra filler via the A-PFFSR. Increasing rotating velocity was propitious to improving frictional heat and material flow, which enhanced joint surface integrity and eliminated interfacial defects. However, the extremely high heat input induced by the rotating velocity of 1800 rpm easily led to the severe joint softening. When the rotating velocity was 1600 rpm, the maximum tensile strength of sound repaired joints was approximately equivalent to that of base ZL210 alloys, realizing the quasi repairing of the ZL210 aluminum alloys. [ABSTRACT FROM AUTHOR]

Radial-additive friction stir repairing (R-AFSR) was proposed to repair exceeded tolerance holes. Here, AZ31 Mg alloys were selected as the primary research object. Good metallurgical bonding appeared in the repaired zones due to atom diffusion induced by thermo-mechanical behaviors. The diameter of the exceeded tolerance hole was reduced from 10 to 8 mm. The stir zone and partial thermo-mechanically affected zone were characterized by fine and equiaxed grains. The average grain size in the stir zone was less than 10 μm, attributing to high microhardness values. A high-quality repaired joint with the maximum tensile strength of 183 MPa was achieved, equivalent to 93.8% of the joint with the standard hole for AZ31 Mg alloys. Compressive shear strength and compression rate of the repaired joint reached 58.4 MPa and 26.1%, up to 75% and 74.6% of the joint with the standard hole. The fracture surface morphologies exhibited the typical ductile fracture. Therefore, R-AFSR has great prospects to repair the exceeded tolerance holes. [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]

Fused deposition modelling is an additive manufacturing technology that is widely employed to produce good quality products with complex geometries at a low cost and with efficient manufacturing and delivery logistics. The mechanical properties can be enhanced by studying the numerous FDM parameters and by using new materials. In this work, was studied the mechanical properties tensile strength, flexural strength, and impact energy of 3D printed parts manufactured with FDM technology and PLA-graphene raw material by varying the infill and layer thickness parameters using a statistical technique CCD—central composite design. Due to the layered production process, 3D printed parts exhibit anisotropic behaviour. In the tests, the flat orientation and honeycomb infill pattern were maintained. The results showed that the mechanical properties improve as the linear layer thickness parameter increases. The behaviour was different in each test for the linear infill parameter. The mechanical properties, tensile strength and flexural strength, increased as the infill increased, while impact energy decreased as infill increased. The relationship between mechanical properties and printing time/weight was also evaluated. [ABSTRACT FROM AUTHOR]

A polymer matrix (epoxy) composite was produced using cow bone particles as reinforcement, and different mechanical tests were performed to evaluate the composite workability. The cow bone (CB) was washed, air dried, and carbonized at a temperature of 750 °C after which they were milled into powder and screened to particle sizes of 150 μm, 300 μm, and 600 μm. The milled cow bone particles were varied from 10 to 60 wt%, and composite materials were produced from them. The mechanical properties of the composites examined include tensile strength, impact strength, and hardness. The effect of carbonization on the mechanical properties of the developed composites was studied in this research. The results show that smaller particles have the best properties. Optimum results were also obtained as the filler loading increased to a value of 40 wt% before decreasing. Better enhancement of property was obtained for the carbonized composites for tensile strength and hardness values, but uncarbonized composites gave better impact strength. The various results obtained are equivalent to those of other agro-waste materials generally used in polymer composite production. Thus, this work shows that cow bone particles can be a useful material for polymer composites production for various mechanical applications. [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]

Refill friction stir spot welding (RFSSW) has been used to weld 6061-T6 aluminum alloy, and keyhole free joints were successfully obtained. Effect of tool rotation speed on microstructure and mechanical properties of joint was investigated. The joint was divided into four zones, i.e., the base material (BM), heat-affected zone (HAZ), thermo-mechanically affected zone (TMAZ), and stir zone (SZ) according to microstructural evolution. Defect was not found on the surface of welded joint, but inner defects of partial bonding, bonding ligament, hook, and voids were observed within the welded joint. The microhardness of HAZ and TMAZ was lower than that of the BM, while the maximum microhardness was obtained in the SZ of welded joints. With increasing tool rotation speed from 1100 to 1700 rpm, microhardness decreased with increasing grain size in the weld. The maximum tensile shear failure load of 7522 N was obtained for the joint under tool rotation speed of 1500 rpm. Two different failure modes of plug fracture and tensile-shear mixed fracture were observed during the tensile shear tests. [ABSTRACT FROM AUTHOR]

Multi-pulse tempering (MPT) on the resistance spot welding (RSW) is a considerable method to improve the quality of spot weld joints. For its uncertain tempering temperature and large temperature fluctuation, some stable sequential coupling finite element (FE) models for RSW and MPT of DP590 dual phase steel are developed to control the tempering temperature and further determine the experimental parameters. The nugget shape and size of simulation are verified by experimental observation, and the effects of MPT on microstructure, microhardness, and mechanical property during tensile-shear loading condition are experimentally investigated. The results show that MPT and its tempering temperature have no effect on the tensile-shear failure mode and have slight impact on nugget size and tensile-shear peak load. Besides, MPT leads to lower nugget hardness and better mechanical properties of spot weld joints than that of ordinary RSW due to the formation of a tempered martensite, and the higher tempering temperature expands these effects of MPT. However, the extent of the impact by MPT temperature on microstructure and mechanical property of spot weld joints is inferior to that of the impact by the MPT process itself. [ABSTRACT FROM AUTHOR]

Evaluation on mechanical properties of a riveted structure with electromagnetic riveting was performed experimentally in this work. The effect of rivet tail dimension on mechanical properties and microstructure evolution were investigated by controlling deformation. The possibility of substituting a riveted structure for a bolted structure was explored by the contrast analysis. Results showed that dislocation slip in the adiabatic shear band was a main deformation mechanism of rivet tail. The rivet tail dimension mainly determined pull-out strength and failure mode of the riveted structure, and the optimal height of rivet tail was 5∼6 mm for this riveted structure. The maximum bearing loads of shear tests and pull-out tests were 23.3 and 35.0 kN, respectively. Both shear strength and pull-out strength of riveted structures exceeded that of bolted structures, where the bolt has similar tensile-loading capacity as the rivet shaft. In contrast to the bolted structure, the load-to-weight ratio values of the riveted structure for shear test and pull-out test were improved by 22.64 and 66.10 %, respectively. [ABSTRACT FROM AUTHOR]

In this work, a new water bath friction stir spot welding (WB-FSSW) process was developed. The effects of dwell time on the microstructures and mechanical properties of the WB-FSSW-welded AZ31 magnesium alloy joints were investigated by microstructural observation, tensile tests, and microhardness tests. It was found that compared with those of ordinary FSSW welds, the WB-FSSW welds have poorer tensile shear force, almost equal tensile shear strength per unit area τ and higher microhardness mainly due to the narrower bonded zone width of the hooks and microstructures in the welded joints, respectively. Moreover, with the increase in the dwell time, the microhardness and the tensile shear strengthen per unit area τ of the WB-FSSW-welded joints increased firstly and then decreased because of the fluctuant evolution of grain size of α-Mg and the volume fraction of the β-MgAl. The optimal dwell time for the WB-FSSW welding was from 10 to 15 s whereby the finest grains and the highest mechanical properties of the welded joints can be achieved. [ABSTRACT FROM AUTHOR]

A 6061-T6 aluminum alloy was self-reacting friction stir welded by using the specially designed tool with unequal shoulder diameters at a constant welding speed of 150 mm/min to investigate the effect of rotation speed on microstructure and mechanical properties of the joints. Excessive flash on the bottom surface of the joint and groove defects on both surfaces of the joint were formed when the lower shoulder diameter was much smaller. The suitable shoulder sizes were determined as 16 and 18 mm in lower shoulder diameter and upper shoulder diameter, respectively. The grain size and the dislocation density in the weld nugget zone (WNZ) increased with increasing rotation speed. The tensile strength of joints first increased with increasing rotating speed and then decreased remarkably as a result of the formation of void defect. The joints welded at lower rotation speeds were fractured in the thermal mechanically affected zone (TMAZ). However, the fracture locations of the defect-free joints were changed to the heat affected zone (HAZ) at higher rotation speeds. [ABSTRACT FROM AUTHOR]