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This research aims to analyze the welding of 1 mm thick NiTinol sheets using an autogenous double pulse tungsten inert gas (DPTIG) welding process. The effect of heat input (HI) on bead geometry, microstructure, hardness, tensile strength, phase transformation temperature (PTT), and corrosion behavior was studied. The lower (111.25 J/mm), and higher (120.14 J/mm) HI produced an average grain size of 26 μm and 36 μm, respectively. The microstructure of the fusion zone (FZ) had coarser columnar grains with intermetallic phases such as Ni3Ti, and TiO2. The grain size in the FZ increased with the increase in HI. Sample P (111.25 J/mm) showed a higher hardness of 280.54 HV and tensile strength of 566 MPa due to a higher proportion of austenite phase (99.4%), the smaller grain size of 26 µm, a larger fraction of high angle grain boundary (HAGB) of 75.8%, and higher kernel average misorientation (KAM) value of 4.93. Compared to base metal (BM), sample P (111.25 J/mm), and sample S (120.14 J/mm) exhibited a reduction in tensile strength of 19.14% and 32.29%, respectively. The decline in hardness and tensile strength was attributed to the formation of intermetallic phases, a decrease in the Ti/Ni ratio, coarser grain formation, and a decrease in HAGB fraction and KAM values. The fractured tensile samples showed a mixed mode of fracture with dimples and cleavage facets. Compared to BM, Sample Q (118.05 J/mm) exhibited lesser variation in temperature hysteresis values for austenite and martensite temperatures, with a deviation of 0.4°C and 3.1°C, respectively. All the welded samples had better corrosion behavior than the BM due to a higher Ti/Ni ratio. [ABSTRACT FROM AUTHOR]

Additive mixed friction stir welding can be an innovative and novel method for enhancing the friction stir welding process. Thus, this research aimed to investigate nano Al2O3 effects on the mechanical and microstructure of FSWed joints using Al alloys AA2024-T351/AA7075-T651. The experiments were performed based on response surface approach based CCD twenty run with varying three factors: tool rotational speed (A: 800-1,200 rpm), welding speed (B: 20-60 mm/min), tool plunge depth (C: 0.2-0.4 mm) and fixed volume percentages of Al2O3 nano-particles (8%). Mechanical performances such as tensile, yield, and hardness tests have been performed and microstructural properties have been analyzed through SEM and microscopy. The statistical analysis shows that the tensile strength can be significantly affected by rotational speed (A), welding speed (B), tool plunge depth (C), interaction (AB, BC, AC), and quadratic term A², B² in the FSW process; yield strength was influenced considerably by main, interaction, and quadratic terms; main factors and quadratic terms A², B² and C² significantly influenced hardness values. The fracture test revealed that the joints with Al2O3-reinforced AA2024-T351/AA7075-T651 alloys were more ductile and less brittle. The optimal conditions for FSW, tool rotational at 1,146 rpm, weld speed at 60 mm/min, and 0.4mm plunge depth were responsible for higher tensile strength of 169 MPa, yield strength of 145 MPa, and micro-hardness values of 89 HRB due to the uniform nano-particle dispersions and better material mixing. [ABSTRACT FROM AUTHOR]

This work optimizes the current (I), voltage (V), flow rate (F), and arc gap (G) of the gas tungsten arc welding (GTAW) of the Ti40A titanium alloy to decrease the heat input (HI) and improve the ultimate tensile strength (TS) and micro-hardness (MH). The radial basis function network (RBFN) was utilized to present performance measures, while weighted principal component analysis (WPCA) and an adaptive nondominated sorting genetic algorithm II (ANSGA-II) were applied to estimate the weights and generate optimal points. The evaluation via an area-based method of ranking (EAMR) was employed to determine the best solution. The results indicated that the optimal I, V, F, and G are 89 A, 23 V, 20 L/min, and 1.5 mm, respectively. The improvements in the TS and MH were 1.2 % and 19.8 %, respectively, while the HI was saved by 18.4 %. The RBFN models provided acceptable accuracy for prediction purposes. The ANSGA-II provides better optimality than the conventional NSGA-II. The HI, TS, and MH of the practical GTAW Ti40A could be enhanced using optimality. The optimization method could be utilized to deal with optimization problems for not only other GTAW operations but also other machining processes. [ABSTRACT FROM AUTHOR]

This paper explores the optimization of Tungsten-Inert-Gas (TIG) welding process parameters for creating a hybrid structure of Aluminium 6061 and Stainless Steel 304 using a copper filler rod (ER-Cu). The Welding of these two materials has industrial relevance owing to its weight reduction capabilities and environmental benefits. However, Aluminium and Stainless-Steel have different melting points and thermal properties. Aluminium has twice coefficient of thermal expansion and six times coefficient of thermal conductance as compared to Stainless-Steel. This difference often results in residual stresses and brittle intermetallic compounds in the weld region. We have chosen the Welding Current, Welding Speed, and Gas Flow Rate as input parameters, and Ultimate Tensile Strength (UTS) and Micro-hardness as response parameters. We have employed the Response Surface Methodology (RSM) using a Box-Behnken design to evaluate the influence of input parameters on UTS and Micro-hardness. Furthermore, an Analysis of Variance (ANOVA) is conducted to determine the input parameters' significance on the response parameters. Our surface plots demonstrate that UTS improves with increased Welding Current and reduced Welding Speed. Simultaneously, Micro-hardness increases with elevated Welding Speed and decreased current, up to a specific limit. The peak value of UTS (79 MPa) was observed with a Current range of 85-90 A, Speed range of 95-100 mm/min, and Gas Flow Rate of 14.5-15 l/min. On the other hand, maximum Micro-hardness (260HV) was obtained with a Current range of 80-85 A, Speed range of 105-110 mm/min, and Gas Flow Rate of 14.5-15 l/min. This research contributes to improving the manufacturing process of hybrid structures, specifically by optimizing the advantages of both Aluminium and Stainless Steel while addressing the challenges that arise during their combination. The study's conclusions have major consequences for sectors looking to take advantage on the mutually beneficial characteristics of different metals in welding applications. [ABSTRACT FROM AUTHOR]

Additive mixed friction stir welding can be an innovative and novel method for enhancing the friction stir welding process. Thus, this research aimed to investigate nano Al2O3 effects on the mechanical and microstructure of FSWed joints using Al alloys AA2024-T351/AA7075-T651. The experiments were performed based on response surface approach based CCD twenty run with varying three factors: tool rotational speed (A: 800–1,200 rpm), welding speed (B: 20–60 mm/min), tool plunge depth (C: 0.2–0.4 mm) and fixed volume percentages of Al2O3 nano-particles (8%). Mechanical performances such as tensile, yield, and hardness tests have been performed and microstructural properties have been analyzed through SEM and microscopy. The statistical analysis shows that the tensile strength can be significantly affected by rotational speed (A), welding speed (B), tool plunge depth (C), interaction (AB, BC, AC), and quadratic term A2, B2 in the FSW process; yield strength was influenced considerably by main, interaction, and quadratic terms; main factors and quadratic terms A2, B2 and C2 significantly influenced hardness values. The fracture test revealed that the joints with Al2O3-reinforced AA2024-T351/AA7075-T651 alloys were more ductile and less brittle. The optimal conditions for FSW, tool rotational at 1,146 rpm, weld speed at 60 mm/min, and 0.4 mm plunge depth were responsible for higher tensile strength of 169 MPa, yield strength of 145 MPa, and micro-hardness values of 89 HRB due to the uniform nano-particle dispersions and better material mixing.

The stainless steel/aluminum multilayer composites were prepared by one-step explosive welding using ammonium nitrate explosive with two different thicknesses. The microstructure and mechanical properties of the multilayer composites were examined. There is a thin metallurgical melting zone at each bonding interface, consisting mostly of iron and aluminum elements. However, the micro-crack appears in the second metallurgical bonding zone obtained using the explosive of 24 mm thickness. The micro-hardness values at the four bonding interfaces are higher than those of bulk 1060 aluminum and 304 stainless steel. The yield strength of the multilayer composites obtained in the two cases is higher than that of the original 304 stainless steel while the tensile strength is between those of the original 1060 aluminum and 304 stainless steel. Meanwhile, the tensile strength and yield strength of multilayer composites obtained by explosive welding with explosive of 20 mm thickness are relatively higher. [ABSTRACT FROM AUTHOR]

Purpose: This paper aims to accomplish friction stir welding (FSW) of Al–Li alloy AA8090 to determine optimal settings of the process parameters for higher tensile strength and higher micro-hardness (MH) to achieve the objective of adequate butt-joint strength. Design/methodology/approach: An empirical relation is implemented to govern the utmost influence parameters, i.e. tool rotation speed (TRS), tool transverse speed (TTS) and dwell time (DT). Taguchi grey relational analysis (GRA) was applied for multi-response optimization of response parameters. The grey relational grades (GRs) have been calculated for both the responses MH and ultimate tensile strength to get optimal parametric settings. The variance test has been performed to check the adequacy of the model. Findings: The Taguchi L9 orthogonal array design was used in establishing the relation between input parameter and output parameter (tensile and MH). TTS and DT have been predicted to be the two most important parameters that influence the extreme quality features of joints by using friction stir welding. Scanning electron microscopy fractography shows the ductile failure of the welded joints. Originality/value: The experimental trials provided the followings results, maximum ultimate tensile strength (UTS) of 219 MPa and MH 107.1 HV under 1,400 rpm of TRS, 40 mm/min of TTS and 8 s of DT founded the optimum value through GRA. [ABSTRACT FROM AUTHOR]

Automotive monocoque is in need of AA7075 with enhanced strength and hardness properties. Fabrication of Surface Hybrid Composites (SHCs) by Friction Stir Processing is a prominent technique to satisfactorily enhance the aforementioned characteristics. SHCs are formed through different volume proportions of Al2O3/SiC reinforcements. Heat generation during the processing stage shows a linear trend along the longitudinal axis due to the thermal conductivity of AA7075. Microstructure of composites is observed with fine grain formation and homogeneous distribution of reinforcements. X-ray Diffraction pattern confirms the existence of both reinforcements in matrix alloy. Specimens with identical volume ratio of Al2O3 and SiC particles depict the superior micro-hardness of 265 VHN which is 8.5 and 19.08% higher than the individual contribution of reinforcements. This is attributed to the homogeneous settlement of reinforcements and particle pinning with parent matrix. Addition of Al2O3 improves the impact toughness due to its wettability with base AA7075 as a result of Al-Al bond. Incorporation of SiC particles enhances the Ultimate Tensile Strength of the composites by virtue of its high load-bearing capacity. Fracto-graphic analysis of the specimens with different Al2O3/SiC weight ratios indicated the fractures along the breakdown of reinforcement particles. [ABSTRACT FROM AUTHOR]

The aluminum (Al) alloy AA7075 is widely used in various industries due to its high strength-to-weight ratio, which is comparable and replaceable to steel in many applications. However, it has poor resistance to wear and corrosion compared to other Al alloys. The conventional pressure die coating with Cr and cadmium has led to premature failure while the load is applied. It is indeed to develop a novel coating method to improve the mechanical, wear, and corrosion properties of AA7075 Al alloy. In the present investigation, the binary and ternary metals such as zinc–nickel (Zn–Ni), zinc–cobalt (Zn–Co), and nickel–chromium–cobalt (Ni–Cr–Co) are electroplated on the substrate material (AA7075). In order to ensure optimal coating adhesion, the surface of the substrate material was pre-treated with laser surface treatment (LST). The mechanical and corrosion studies have been carried out on the uncoated and coated materials. It is observed from the findings that the ternary coating has higher wear resistance than the binary-coated material. The ternary coating has 64% higher resistance in the non-heat-treated status and 67% higher resistance in the heat-treated condition compared to the uncoated specimens. The tensile strength (MPa) of Ni–Cr–Co on AA7075 pressure die casting (PDC) is higher than the other deposits (582.24 of Ni–Cr–Co > 566.07 of Zn–Co > 560.05 of Zn–Ni > 553.64 of uncoated condition). The presence of a crystalline structure with the high alignment of Co and Ni atoms could significantly improve the corrosion resistance of Ni–Cr–Co coatings on AA 7075 PDC substrates when compared to binary coatings. The scanning electron microscopy (SEM) images, X-ray diffraction (XRD), and X-ray photoelectron spectroscopy findings on the coated materials have been corroborated with the analyses on mechanical and corrosion properties. The XRD analysis of the Zn–Ni binary coating has reported that the diffraction peaks of γ-NiZn3 (831), γ -Ni2Zn11 (330), and 631 with 2θ values 38, 43, and 73° are confirming the presence of Zn–Ni binary deposit on AA7075 PDC substrate. The XRD pattern of Zn–Co-coated material has revealed that the presence of three strong peaks such as Zn (110), Co (111), and CoZn (211) and two feeble peaks such as ε-CoZn3 (220) and ε-CoZn3 (301) are clearly visible. The XRD pattern of Ni–Cr–Co ternary coating has exhibited that the Ni–Cr–Co ternary deposit is a solid solution with a body-centered cubic structure due to the formation peaks at lattice plane such as (110), (220), and (210) with a crystal lattice constant of 2.88 A°. The SEM image for both the binary- and ternary-coated materials has exhibited that the deposited surface has displayed many shallow pits due to hitting by progressive particles. The SEM image has illustrated the presence of Zn–Ni atoms with smaller globular structure. The surface morphology of binary Zn–Co coating on the PDC AA7075 substrate has unveiled the evenly distributed dot-like structure and submerged Co particles in the galaxy of Zn atoms. To understand the effectiveness of bonding by laser texturing, cross-section SEM has been carried out which furthermore revealed the effective adhesion of Ni–Cr–Co on AA7075 PDC; this could also be the reason for the enhancement of microhardness, wear, and corrosion resistance of the said coating.

In the present study, a defect-free dissimilar weld joint of AA5083 and AA6061 was fabricated, and the influence of SiC particles with multi-pass friction stir welding (FSW) on the microstructural evolution and various mechanical behaviors was investigated. A constant tool rotational speed of 950 rpm, traverse speeds of 30 mm/min and tool tilt angle of 1° were used as welding parameters. The results revealed that increasing the number of FSW passes from one to three improved the particles dispersion, which improved the tensile strength, %elongation, and micro-hardness of the FSWed joint via the pinning effect. After implementation of one, two and three FSW passes, the tensile strength of the FSWed joints was observed as 244.31, 251.58 and 266.87 MPa, and the %elongation was observed as 27.4, 29.8 and 32.7%, respectively. Furthermore, the micro-hardness after one, two and three FSW passes was observed to be 116.4, 120.8 and 128.4 HV, respectively. [ABSTRACT FROM AUTHOR]

This study focuses on the effect of three different cooling conditions during multi-scan laser bending of duplex stainless-steel sheet. Results show that the trend of temperature distribution with number of scans is almost similar in all three conditions, but the peak temperature changes. The bend angle, heat affected zone, tensile strength and hardness are significantly affected by the cooling condition. The tensile strength and hardness of scanned specimen is increased compare to base material in all three cooling conditions. The microstructure shows grain refinement and sigma phase formation at the top and bottom surfaces, respectively, in all three cooling conditions. [ABSTRACT FROM AUTHOR]

In the present study, friction stir welding was employed to successfully fabricate a weld joint of dissimilar aluminum alloys AA7075 and AA6061 reinforced with SiC microparticles. The influence of dispersion pattern of different volume fractions of SiC microparticles under different processing parameters such as rotational speed and traverse speed on microstructural and mechanical behavior was examined. The outcomes demonstrated that dynamic recrystallization and pinning effect of dispersed SiC particles in the SZ, resulting in grains refinement. which significantly influenced the tensile strength, strain rate and micro-hardness. FSWed joints reinforced with higher volume fraction of SiC particles revealed higher mechanical properties. Consequently, FSWed joint produced at rotational speed of 1100 rpm and traverse speed of 40 mm/min incorporated with 10% SiC particles exhibits the higher tensile strength of 261.20 MPa with nearly 91% of joint efficiency and maximum micro-hardness of 186.83 HV, which is approximately 10% higher than the hardness of as received AA7075 base material. [ABSTRACT FROM AUTHOR]

The research aimed to find a physical strengthening method for thin-sheet metal parts using an ultrasonic shot peening (USP) method at room temperature. Herein, the influence of the USP treatments on the surface roughness, microstructure, micro-hardness, and tensile strength of the TC2 thin-sheet with a thickness of 0.5 mm was investigated systematically. The results showed that the Ra of the TC2 thin-sheets increased to 0.374, 0.418 and 0.479 μm after the USP treatments with the intensities of 0.189, 0.277 and 0.360 mmA, respectively. Compared with pneumatic shot peening (PSP) of similar Almen intensity, the surface quality of the alloy after USP treatment was significantly improved. The cross-sectional micro-hardness curves of the USP-treated TC2 thin-sheet showed ‘V’ shapes, and the micro-hardness of the surface layer increased as the shot peening intensity increased. When the Almen intensity was 0.360 mmA, the corresponding maximum micro-hardness of the surface layer was 362.9 HV0.025, which was 67.9 HV0.025 larger than that of the initial alloy. The USP treatment also improved the tensile strength of the TC2 thin-sheet, and the tensile strength increased as the shot peening intensity increased. When the Almen intensity was 0.360 mmA, the tensile strength was increased by about 6.23%, reaching 799.3 MPa. Therefore, the USP treatment method is a potential physical strengthening method for thin-walled parts at room temperature.

Purpose: This paper aims to predict the performance of friction stir welded AA8090 joint. Design/methodology/approach: In the present study, Al-Li AA8090 plates are butt joined using friction stir welding (FSW). The experiments are designed and optimized using a Taguchi-orthogonal array. The experiments are conducted at three different process parameters, i.e. tool rotational speed (TRS), tool transverse speed (TTS) and dwell time (DT). The ultimate tensile strength (UTS) and microhardness (MH) are considered as response parameters. In addition, a statistical tool (ANOVA) is used to check the adequacy of experiment results. Findings: The maximum UTS of 220 MPa is obtained at a TRS of 1,400 rpm, tool TTS of 40 mm/min and DT of 15 s. The maximum microhardness is obtained for 1,400 rpm, 25 mm/min and 8 s, i.e. 108.6 HV. The microstructural showed that the minimum grain is observed at the nugget zone. Fractography analysis revealed the ductile behaviour of fractured surfaces. Originality/value: From the reported literature, it has been observed that very limited work is reported on the FSW of AA8090 alloy. Further, the thermal behaviour of welded joint is also observed in this experimental work. [ABSTRACT FROM AUTHOR]

In this research, a defect-free dissimilar weld joint of AA7075-T6 and AA6061-T6 reinforced with Al2O3 nanoparticles was fabricated via friction stir welding (FSW). The influence of tool rotational speed (700, 900 and 1100 rpm), traverse speed (40, 50 and 60 mm/min) with varying volume fractions of Al2O3 nanoparticles (4%, 7% and 10%) on microstructural evolution and mechanical properties were investigated. The augmentation of various mechanical properties is based on the homogeneity of particle dispersion and grains refinement in the SZ of the FSWed joint. The findings revealed that the remarkable reduction in grain size in the SZ was observed owing to the incorporation of Al2O3 nanoparticles produces the pinning effect, which prevents the growth of grain boundaries by dynamic recrystallization (DRX). The increasing volume fraction of Al2O3 nanoparticles enhanced the mechanical properties such as tensile strength, % elongation and micro-hardness. Agglomeration of particles was observed in the SZ of the FSWed joints produced at lower tool rotational speed of 700 rpm and higher traverse speed of 60 mm/min due to unusual material flow. Homogenous particle dispersion and enhanced material mixing ensue at higher rotational speed of 1100 rpm and lower traverse speed of 40 mm/min exhibit higher tensile strength and micro-hardness. [ABSTRACT FROM AUTHOR]

Reinforced magnesium metal matrix nanocomposites (MMMNCs) have piqued the interest of scientific community in recent years. Friction stir processing (FSP) is a known process to achieve the highest level of secondary phase nanocomposites distribution in the base monolithic matrix. In this study, an attempt has been made to synthesize magnesium base AZ61A/n-TiC nanocomposites using FSP and the influence of tool rotational speed on the metallurgical, mechanical, and tribological behavior of the developed composites has been studied. Microstructural examination shows that as tool rotational speed increases, high plastic deformation occurs and heat is generated along with the concomitant shattering impact of rotation, which consequently develops larger grains in the stir zone. However, this also provides thrusts resulting in uniform distribution of the nanoparticles in the base matrix. Microhardness and ultimate tensile strength of the developed nanocomposite were found to be significantly improved when contrasted with the base metal. Lower wear rate was observed for the composite developed at 800 rpm along with the abrasive type of wear mechanism. [ABSTRACT FROM AUTHOR]

Present study introduces effect of forge application and elimination on microstructural and mechanical properties of AISI 316 during friction welding. Temperature measurements, microstructure, micro-hardness, tensile test, scanning electron microscopy and X-ray diffraction were evaluated. Maximum temperature recorded was 819°C while forge was applied between 357°C-237°C. Thermo-mechanically affected zone and highly plastically deformed zone were created at the interface at elimination and application of forge respectively. Ultimate tensile strength decreased and ductility increased when forge elimination compared to forge application. Tensile fracture was occurred adjacent to the welding interface for both cases, though, after forge application, ductile fracture mode and cleavage features through the fingerprints were observed in the fracture morphology. Redistribution and concentration of gamma iron in 111 level after forge application and heat treated of AISI 316. [ABSTRACT FROM AUTHOR]

Tungsten inert gas (TIG) welding is the most commonly used joining process for aluminum alloy for AA6061 and AA7075 which are highly demanded in the aerospace engineering and the automobile sector, but there are some defects occur during TIG welding like micro-crack, coarse grain structure, and porosity. To improve these defects, the TIG welded joint is processed using friction stir processing (FSP).This paper presents the effect of friction stir processing on TIG welding with filler ER4043 and ER 5356 for dissimilar aluminum alloy AA6061 and AA7075. The mechanical characterization, finite element formulation and mathematical equations of heat transfer of TIG + FSP welded joints are investigated using ANSYS Fluent software by adjusting process parameters of FSP. The results show that the maximum compressive residual stress 73 MPa was obtained at the fusion zone (FZ) of the TIG weldment with filler ER4043, whereas minimum compressive residual stress 37 MPa was obtained at stir zone (SZ) of the TIG + FSP with filler 5356. The maximum heat flux 5.33 × 106 W/m2 and temperature 515 °C have observed at tool rotation 1600 rpm with a feed rate of 63 mm/min. These results give a satisfactory measure of confidence in the fidelity of the simulation

In this work, multi-pass friction stir processing (FSP) was successfully applied to AA6061 to reinforce SiC nanoparticles producing defect-free processes. It can be inferred that Nano SiC particles were fragmented totally and uniformly distributed in sixth pass FSP. Agglomeration of SiC particles decreases with increases in the number of FSP pass. In the first pass, the SiC powder with lower formability than the base metal was concentrated inside the groove, so their flow was difficult, and most of them remained at the center of the SZ. The amount of SiC in the surface composite was further decimated after the second pass FSP cycle. At the same time, a progressive and substantial fragmentation of SiC particles ensues after the fourth and sixth passes, respectively, due to improving material mixing and dispersion. The tensile strength of AA6061 exhibited 275.7 MPa, and a percentage strain of 10.9. After implementing multi-pass FSP with nanoparticles of SiC on the AA6061, the tensile properties were enhanced simultaneously as the FSP pass increases. The tensile strength of one pass, two passes, four passes, and six passes was observed as 291.8, 307.5, 330.5, and 348 MPa, respectively, caused by strain-free fine grains during dynamic recrystallization mechanism. In contrast, Vickers's hardness value along the centerline (stir zone) was observed as 101, 119, 125, and 134 HV with 1, 2, 4, and 6 FSP pass, respectively. [ABSTRACT FROM AUTHOR]

The proposed study deals with the joining of AA6061 T6 alloy using a novel geometric square wave tool path pattern for adequate mixing of materials with increased stirring time and enlargement of the deformation zone. Experiments were conducted based on the process parameters to imply the stirring effect like rotation speed 1200 rpm, weaving rate 100 mm/min; and specific step sizes (1.0, 1.5, and 2.0 mm). Results show that the Percentage of variation for achieving the higher tensile strength of 11.3%, micro vickers hardness of 12.8% with a step size of 1 mm compared to the linear weldment. The SEM morphologies of the weldment clarify the formation of IMCs like spheroidal cementite with the zeolitic structure for resulting in higher hardness value. The EDAX results confirm the formation of intermetallic precipitates like Mg2Si that leads the precipitation hardening and grain boundary strengthening. [ABSTRACT FROM AUTHOR]

In this research, copper (Cu) donor material-assisted friction stir welding (FSW) of AA6061-T6 alloy was studied. Cu-assisted FSW joints of AA6061-T6 alloy were prepared at a constant tool rotational rate of 1400 rpm and various welding speeds at 1 mm/s and 3 mm/s. The Cu donor material of different thickness (i.e., 20%, 40%, and 60%) with respect to the workpiece thickness was selected to assist the FSW joining at the plunge stage. It is observed that the downward force generated in the FSW process was gradually decreased after introducing Cu donor material with incremental thicknesses with respect to workpiece at the plunge stage. Post-weld analysis was characterized in terms of microstructure and mechanical properties. The results of microstructure analysis at the stir zone (SZ) show the formation of finer grains due to dynamic recrystallization and plastic deformation. Micro-hardness tests reveal that the hardness decreased from the base metal (BM) to the SZ across the heat-affected zone (HAZ) and thermo-mechanically affected zone (TMAZ). The lowest value of hardness appeared in the TMAZ and HAZ where tensile failure occurs. With increasing welding speed, the average hardness in the SZ decreased due to lower heat input and faster cooling rate. Tensile test plots show no significant change in ultimate tensile strength with or without Cu donor material. Fractography of tensile tested samples shows both ductile and brittle like structure for given welding parameters. This proposed work of FSW with Cu donor material is promising to increase tool life due to the decrement of the downforce during plunge and throughout the welding stage. Meanwhile, the inclusion of donor material did not compromise the weld quality in terms of the mechanical properties and micro-hardness. [ABSTRACT FROM AUTHOR]

In the present study, addition of nano silicon carbide particulates (nSiCp) in the matrix of aluminium alloy 7075 (AA7075) in different weight proportions (0 %, 0.5 %, 1 %, 1.5 %, 2 % and 2.5 %) are done by means of ultrasonic cavitation assisted stir casting technique. The distribution of reinforcing elements was visualized using Field Emission Scanning Electron Microscope (FESEM) image, which reveals that uniform distribution is possible with 1.5 % of nSiCp addition after which agglomeration of nanoparticles is observed. It is observed that with 1.5 % addition of nSiCp mechanical properties gets enhanced, after which it gets reduced. Compared with as cast alloy, tensile strength is improved by 188.17 % and micro-hardness by 48.58 % with a reduction in % elongation by 48.57 % and increase in impact strength by 73.17 % decrease in corrosion rate by 39.44 % is achieved with 1.5 % nSiCp addition with AA7075. Wear resistance tends to improve by 25 % with an increase in the coefficient of friction by 14.18 % with 1.5 % addition of nSiCp. With higher addition of nSiCp above 1.5 %, properties tend to lower due to clustering of nSiCp, which eventually lowers the surface area of nSiCp. [ABSTRACT FROM AUTHOR]

In this work, aluminum matrix composite (AMC) was successfully fabricated by multi-pass friction stir processing (MPFSP) with nanoparticles SiC. A constant rotational tool speed of 1350, feed rate of 65 mm/min, tilt angle of 2° was used to enhance the microstructure and mechanical properties of multi-pass FSP/SiC of AA6082-T6. It can be observed that Nanoparticles SiC were fragmented totally and uniformly distributed in fifth pass FSP. Agglomeration of SiC decreases with increases in the number of passes. The ultimate tensile strength (UTS) of base metal AA6082 exhibited 215.54 MPa, and % strain of 24.91. After implementing multi-pass FSP with nanoparticles of SiC on the AA6082, the UTS was enhanced simultaneously as the FSP pass increases. The UTS of 1st pass, 2nd pass, 3rd pass, 4th pass, and 5th pass was observed as 223.61 MPa, 238.37 MPa, 255.63 MPa, 281.79 MPa and 296.86 MPa, respectively caused by strain-free fine grains during dynamic recrystallization (DRX) mechanism. In contrast, Vickers's hardness value along the centerline (stir zone) was observed as 89, 101, 119, 125, 133 HV with 1st pass, 2nd pass, 3rd pass, 4th pass, and 5th pass respectively.

In this exploration study, friction stir welding of Al-Li 8090 alloys has been accomplished for the optimization of process parameters for determined joint strength. Taguchi's L9orthogonal array (OA) has been used for different three parameters-tool rotational speed, tool traverse speed, and dwell time. To optimize, multi-response had been carried out through Taguchi's-based design of expert. It has been designed for all three responses--ultimate tensile strength, and micro hardness, microstructure. Thermal behaviour analysis shows the temperature variation during friction stir welding at different parameters. Analysis of variance has been used as a tool for obtaining DOE-OA to determine the significant process parameter. Tool traverse speed and dwell time has been predicted the two utmost significant parameters which influence extreme quality features of joint by friction stir welding. Validation of the probable value obtains by confirmation experiments at optimal sets shows the worthy agreement with the values of the experimental outcomes. [ABSTRACT FROM AUTHOR]

• Effect of process parameters is studied under natural and forced cooling conditions during laser bending of mild steel. • Forced cooling has significantly enhanced the deformation during laser bending of mild steel. • Mechanical and metallurgical characterization of laser bent specimens is carried out. • Mechanical properties are improved and a fine grain structure is obtained in the irradiated region. Laser bending is an innovative sheet metal forming technique. Researchers are focusing optimizing the process for enhancing bend angles and mechanical properties. To achieve this, a waiting period between laser scans is vital to re-establish the temperature gradient and improve bend angles. Forced cooling is a critical element in reducing this waiting time. This study investigates the influence of cooling environments (natural and forced cooling) during laser bending of mild steel sheets. It examines the impact of key parameters such as laser power, scan speed, and beam diameter under both cooling conditions. The results reveal that under forced cooling, specific combinations of process variables lead to exceptional outcomes. Notably, a bend angle of 8.81° is achieved with higher laser power (1000 W) and slower scan speed (1000 mm/min) in forced cooling condition. This study also analyzes temperature variations concerning laser power, scan speed, beam diameter, and the number of scans. Furthermore, under forced cooling conditions, an increase in ultimate tensile strength and micro-hardness is observed within the irradiated region. The highest micro-hardness value of 198.5 HV, was attained under forced cooling conditions at 1000 W of laser power and a scan speed of 1000 mm/min. This research underscores the potential of forced cooling mechanisms to significantly enhance laser bending outcomes, encompassing both bend angles and material properties. [ABSTRACT FROM AUTHOR]

Due to loss of structural strengthening at temperatures beyond 250°C, heat-treated aluminium alloys (e.g. AA 6061-T6) weldments are usually characterized with poor mechanical properties including hardness, tensile and impact strengths. In this work, friction stir weldments of AA 6061-T6 reinforced with the additions of SiC, B4C and Al2O3 particles at the joints were produced and investigated for improved hardness, tensile strength and impact strength over the unreinforced weldment. The results showed that the entire reinforced welded joint exhibited improved hardness because of the enhanced metal matrix grain refinement and inherent high hardness of the reinforcement particles. B4C particle addition produced hardest joint of about 81% of the base metal hardness (∼114 HV0.3). The impact energies of the SiC (16.9 J), B4C (16.5) and Al2O3 (12.2 J) reinforced weldments are closer to that of the base metal (18.6 J) compared with the unreinforced weldment (9.6 J). The reinforced weldments showed no significant improvement over the tensile strength of the unreinforced weldment. B4C and SiC reinforcements produced the highest improvements in the hardness (at the joint) and impact strength of the AA 6061-T6 friction stir weldments, respectively. [ABSTRACT FROM AUTHOR]

Tungsten inert gas (TIG) welding is the most commonly used joining process for aluminum alloy for AA6061 and AA7075 which are highly demanded in the aerospace engineering and the automobile sector, but there are some defects occur during TIG welding like micro-crack, coarse grain structure, and porosity. To improve these defects, the TIG welded joint is processed using friction stir processing (FSP). This paper presents the effect of friction stir processing on TIG welding with filler ER4043 and ER 5356 for dissimilar aluminum alloy AA6061 and AA7075. The mechanical characterization, finite element formulation and mathematical equations of heat transfer of TIG þ FSP welded joints are investigated using ANSYS Fluent software by adjusting process parameters of FSP. The results show that the maximum compressive residual stress 73 MPa was obtained at the fusion zone (FZ) of the TIG weldment with filler ER4043, whereas minimum compressive residual stress 37 MPa was obtained at stir zone (SZ) of the TIG þ FSP with filler 5356. The maximum heat flux 5.33 ± 106 W/m2 and temperature 515 °C have observed at tool rotation 1600 rpm with a feed rate of 63 mm/min. These results give a satisfactory measure of confidence in the fidelity of the simulation. [ABSTRACT FROM AUTHOR]

Background: To investigate the effect of complete rupture of the posterior cruciate ligament (PCL) on the biomechanics and histology of the medial collateral ligament (MCL). Materials and methods: Seventy-two male rabbits were randomly divided into two groups: the ruptured group was treated with complete PCL amputation, while the intact group was only subjected to PCL exposure without amputation. Eighteen rabbits were randomly sacrificed at 8, 16, 24, and 40 weeks after the operation, and their specimens were processed for mechanical tensile testing, nano-indentation experiments, hematoxylin-eosin (HE) staining, and picrosirius-polarization staining. Results: There was no significant difference in the length and maximum displacement of the MCL between the ruptured group and the intact group at each time point. The maximum load of the ruptured group was significantly smaller than that of the intact group at 40 W. The elastic modulus and micro-hardness of the ruptured group increased significantly at 24 W and decreased significantly at 40 W. At 16 W and 24 W after PCL rupture, the number of type I collagen fibers and type III collagen fibers in the MCL of the ruptured group was significantly increased compared with that of the intact group. While the type I collagen fibers of the ruptured group were significantly decreased compared with the intact group at 40 W, there was no significant difference in type III collagen fibers between the ruptured group and the intact group. Conclusion: PCL rupture has no significant effect on the mechanical and histological properties of MCL in a short period of time under physiological loading, but the histological and mechanical properties of MCL decrease with time. [ABSTRACT FROM AUTHOR]

In this work, we examine TIG welded joints processed with friction stir processing at tool rotational speeds (TRSs) of 700, 800, 900, 1000, and 1100 rpm, with a constant feed rate of 70 mm/min and tilt angle of 1°. The percentage improvement in the tensile strength of TIG + FSP (TF) weldments was observed to be 78.57 and 75.89%, compared with TIG welded joints with ER4043 and ER5356 filler, respectively, at a TRS of 1100 rpm. A maximum tensile strength of 196 MPa was observed in a TF welded joint with ER5356 filler, and a minimum tensile strength of 98 MPa was observed in the TIG weldment with ER4043 filler. Cleavage facets, tear ridges, and large dimples were observed in fractured specimens of TIG welded joints, whereas fine, equiaxed dimples were observed in TF welded joints. A maximum micro-hardness of 137 HV in the stir zone was observed in TF welded joints at a TRS of 1100 rpm. TF welded joints with ER5356 filler had superior wear resistance compared to TIG and TF welded joints with ER4043 filler. [ABSTRACT FROM AUTHOR]

Joining of dissimilar aluminum alloys are required in many engineering applications. The fusion welding often results in defective weld like porosity, micro cracks, coarse grain structure and high residual stress. To avoid these defects the top surface of Tungsten inert gas (TIG) welded joint are processed using friction stir processing (FSP). In this work, The influences of friction stir processing on the TIG welding with filler wire ER4043 and ER5356 for dissimilar aluminum alloy AA6061 and AA7075 were carried out and investigate the residual stresses and mechanical properties of (TIG+FSP) welded joint and analyze the finite element formulation and mathematical equations of heat transfer and material flow of TIG + FSP welded joint using ANSYS fluent software by adjusting the processing parameters of FSP. The results show that the maximum compressive residual stress 64 MPa were obtained at the fusion zone (FZ) of the TIG weldment with filler ER4043, whereas minimum compressive residual stress 39 MPa was obtained at stir zone (SZ) of the TIG+FSP with filler 5356. The maximum heat flux 5.33 × 106 W/m2 and temperature 511 °C were observed at tool rotation 1300 rpm with feed rate 44 mm/min. These results give the satisfactory measure of confidence in the fidelity of simulation.

The joining of dissimilar materials is required in many engineering and defense applications, and the conventional fusion welding often results in defective welds. The friction stir welding has minimized the welding defects, but not completed. This work focuses on the effect of friction stir processing on TIG-welded joints with filler ER 5356 to improve the mechanical properties of TIG-welded joints. In this paper, the FSP tool pin rotates on an already welded joint by TIG welding to lower the welding load and improve the weld quality by adjusting the processing parameters of friction stir processing. After analyzing the mechanical properties of TIG + FSP-welded joint, computational fluid dynamics-based numerical model was developed to predict the temperature distribution and material flow during TIG + FSP of dissimilar aluminum alloys AA6061 and AA7075 by ANSYS fluent software. The minimum compressive residual stress 18 MPa, maximum tensile strength (281.1 MPa) and hardness (107 HV) were located at the nugget zone of the TIG + FSP weldment at tool rotation speed of 1300 rpm, traverse speed of 30 mm/min and tilt angle 2°. The predicted peak values of temperature at the weld region were calculated and the maximum temperature (505 °C) and maximum heat flux (2.93 × 106 w/m2) were observed at a tool rotation of 1300 rpm. [ABSTRACT FROM AUTHOR]

In this study, AISI D2 tool steel was thixowelded with AISI 304 austenitic stainless steel by using a direct partial remelting technique. The joining parameters (temperature, soaking time, and contact area) have been investigated by studying their effects on the mechanical and metallurgical properties of the thixowelded joint. The joint interfacial microstructures were investigated by optical microscopy, scanning electron microscopy equipped with an EDX analyzer, and x-ray phase analysis was performed to identify the phase evolution. Mechanical characterization was determined by tensile and micro-hardness tests. Maximum tensile strength that was achieved is 635 MPa at 1300 °C, with a 5 mm insert diameter and 10 min holding time. This represents 80% of the D2 base metal strength. The joints were fractured on the D2 base metal side close to the diffusion zone characterized by brittle fracture. Consequently, the joints also achieve a full penetration weld with a smooth and uniform hardness profile. [ABSTRACT FROM AUTHOR]

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• Aluminum 6061-T6 plates were joined with low-carbon galvanized steel by FSSW. • Due to the low process temperature, the steel microstructure did not change. • The intermetallic layer has a direct effect on the quality and strength of the joint. • By increasing the length of pins the tensile strength was improved. Friction stir welding is an efficient method for joining steel and aluminum plates at a point of disturbance. In many studies, the tool is only introduced into the aluminum plate, avoiding penetration into the steel plate due to its high strength and the need for a robust tool. Under such conditions, the created connection usually possesses low mechanical properties. In this research, by increasing the strength of the H13 steel tool through thermal operations, the possibility of penetration and bonding of aluminum 6061 with galvanized low-carbon steel has been provided. Moreover, by penetrating the steel plate, the integration of galvanized layers in the disturbance region has been facilitated. The examined variable parameters include pin length, rotational speed, and tool dwell time. Mechanical properties such as tensile strength, fracture force, and Vickers hardness were investigated. Furthermore, the weld microstructure and intermetallic layers were examined using scanning electron microscopy (SEM) and EDS analysis. Tensile and shear strength increase with an increase in pin length, rotational speed, and tool dwell time. Shear fracture loading showed a decrease with increasing pin length, then reached its maximum value when using long pins, while continuously increased with higher rotational speed and longer tool dwell time. As we approach the center of the weld in both the steel and aluminum parts, smaller grain sizes are observed due to increased plastic deformation, more material mixing, and increased mechanical tool pressure, while in the heat-affected zone, a coarse grain structure forms. Hardness in the aluminum plate decreased in the heat-affected zone and reached its minimum value in the thermo-mechanical-affected zone, then increased to the maximum value in the nugget zone, while hardness changes in the steel plate were uncertain. The most influential parameter on mechanical and microstructural properties was pin length, followed by rotational speed and tool dwell time. [ABSTRACT FROM AUTHOR]

In this study, effects of the process parameters on the mechanical and micro-structural properties of friction stir welded (FSW) joint of AA6061-T6 have been studied. Welding of aluminium alloy by conventional method is difficult. Therefore friction stir welding which is a solid state welding process, is emerging as a preferred method. After experimentation six samples were prepared at different process parameter i.e. rotational speed of 500, 710 and 1000 rpm along with welding speed of 25 and 40 mm/min. Tensile test and micro-hardness test were conducted on the samples to analyze the mechanical properties. Fractured surface of the tensile samples were also examined with field emission scanning electron microscope (FESEM). Microstructure of FSW joints were analysed with the help of optical microscopy (OM) as well as with FESEM. Different aspects of temperature development during the process were investigated using infrared thermal camera. [ABSTRACT FROM AUTHOR]

In the present research, friction stir processing (FSP) of as-cast AZ91-D Mg-alloy has been done to improve its ultimate tensile strength (UTS). Taguchi's L-9 orthogonal array was used to optimize the process parameters for improving the UTS of AZ91-D parent material (PM). The optimum levels of process parameters were found to be 1000 rpm, 50 mm min-1 and 6 passes for the rotational tool speed, transverse speed and a number of passes of FSP, respectively. As per ANOVA results, the number of passes has the highest statistical effect of about 41.3% on UTS. Additionally, the micro-hardness tests were conducted to confirm the process optimization. The FSPed material with optimized parameters showed an enhancement of 24.56 and 77.5% in UTS and micro-hardness as compared to PM respectively. The grain size of FSPed material was observed to be 6.88 times lesser than PM. Microstructure evaluation of optimized FSPed material also confirmed the uniform dispersion of ß-phase (Mg17Al12) resulting in improved properties. [ABSTRACT FROM AUTHOR]

The effects of thermal ageing time and temperature used during heat-treatment were studied on tensile strength, elongation, and microhardness of the laser welded Nb-1%Zr-0.1%C alloy in continuous wave mode. Post-weld heat treatment (PWHT) was carried out by varying the temperature and time in the ranges of (850–1050) °C (that is, about the recrystallisation temperature) and (0.5–4) h (as the weld samples were prepared in the form of sheets), respectively. The grain sizes of fusion zone (FZ), and FZ heat treated at 850 °C for 4 h and that at 950 °C for 2 h were found to be equal to 52.85 μm, 84.89 μm and 116.43 μm, respectively. The segregation of zirconium, carbon and oxygen increased grain boundary energy and induced brittleness to the grain boundary, resulting in loss of ductility. The micro-hardness and Young's modulus values were observed to increase in the FZ compared to that of the base metal (BM), but their decreasing trends were noticed during the heat-treatment due to the grains' softening. For the PWHT samples, the plasticity was found to decrease to about 57% of that of BM. This was attributed to the precipitation of carbides, grain growth, and dislocation pinning during the ageing process. During the heat-treatment of the welded samples, both Yield Strength (YS) and Ultimate Tensile Strength (UTS) were found to decrease to 77% and 86%, respectively, of that of the BM. • Deals with laser welding of Nb-1%Zr-0.1%C alloy. • Studies the effects of heat-treatment on mechanical properties. • Heat-treatment of the weld decreases YS and UTS • Heat-treatment of the weld decreases plasticity. • Heat-treatment decreases the micro-hardness and Young's modulus of the weld. [ABSTRACT FROM AUTHOR]

The purpose of this paper is to optimize the process parameter to get the better mechanical properties of friction stir welded AM20 magnesium alloy using Taguchi Grey relational analysis (GRA). The considered process parameters are welding speed, tool rotation speed, shoulder diameter and plunging depth. The experiments were carried out by using Taguchi's L18 factorial design of experiment. The processes parameters were optimized and ranked the parameters based on the GRA. The percentage influence of each process parameter on the weld quality was also quantified. A validation experimental run was conducted using optimal process condition, which was obtained from the analysis, to show the improvement in mechanical properties of the joint. This study also shows the feasibility of the GRA with Taguchi technique for improvement in welding quality of magnesium alloy.

S136 mould steel with excellent corrosion resistance has been widely applied in the mould industry. However, in order to meet the increasing demands of injection products with complex structure and high quality, selective laser melting (SLM) as a novel manufacturing method is chosen due to its rapid fabricating parts with complex geometric shapes. Further, it is essential to enhance their hardness and wear property to prolong the service life of injection mould. In this work the reinforced S136 mould steel with different TiB 2 contents (0, 0.5, 1.5, 2.5 wt%) are fabricated by SLM. The optimal TiB 2 content is determined to be 0.5 wt%, which the SLM S136 composites show the finest grains and have an enhanced tensile strength (982.8 Mpa), an elevated micro-hardness (761.5 Hv), a reduced coefficient of friction (0.6489) and a considerably low wear rate (0.152 × 10 −4  mm 3 /N m). Here we demonstrate that these superior performances benefited from the novel microstructure, that is, the dispersed TiB 2 nanoparticles bonded with each other in a highly homogeneous way to form refined, continuous and well-distributed ring-like structures, which were comprised of thin “metal-ceramic” interface along the grain boundaries. It mainly contributed to the grains refining and grain boundaries strengthening. [ABSTRACT FROM AUTHOR]

This report presents the results of experimental work on the mechanical properties of coral aggregate concrete (CAC) containing fly ash (FA) and silica fume (SF). The aim of this study was to investigate the effects of FA and SF on the fresh and aged mechanical properties of CAC. Apart from the workability of the fresh concrete, the compressive strength, splitting tensile strength, capillary water sorptivity, chloride penetration, and micro-hardness of the interfacial transition zone (ITZ) were measured. CAC with only ordinary Portland cement as the binder was used as the control mixture. The results indicated that the cohesiveness and water retention of CAC were improved by the addition of FA and SF under the condition of equal slump. CAC showed lower compressive but higher splitting tensile strength, water sorptivity, and chloride penetration compared to normal concrete because of its porous and rough surface and the high water absorption of the coral aggregate itself. FA and SF have different effects on improving the mechanical properties, durability, and structure of the ITZ of CAC. FA had a negative effect on strength at early ages, but significantly enhanced the later-age strength, while SF had a positive effect at all ages. Similar results were obtained in the chloride penetration test. However, it was found that, besides improving the compressive strength and the splitting tensile strength, the combination of FA and SF had a positive effect in reducing the water sorptivity and chloride permeability, as well as improving the micro-hardness in the ITZ, of CAC. The above properties of CAC containing 25% FA and 5% SF as partial replacements for cement are superior to those of CAC containing 5% SF alone. [ABSTRACT FROM AUTHOR]

The microstructural and mechanical behavior of hybrid metal matrix composite based on aluminum alloy 6082-T6 reinforced with silicon carbide (SiC) and boron carbide (B4C) particles was investigated. For this purpose, the hybrid composites were fabricated using conventional stir casting process by varying weight percentages of 5, 10, 15, and 20 wt% of (SiC + B4C) mixture. Dispersion of the reinforced particles was studied with x-ray diffraction and scanning electron microscopy analyses. Mechanical properties such as micro-hardness, impact strength, ultimate tensile strength, percentage elongation, density, and porosity were investigated on hybrid composites at room temperature. The results revealed that the increase in weight percentage of (SiC + B4C) mixture gives superior hardness and tensile strength with slight decrease in percentage elongation. However, some reduction in both hardness and tensile strength was observed in hybrid composites with 20 wt% of (SiC + B4C) mixture. As compared to the un-reinforced alloy, the improvement in hardness and tensile strength for hybrid composites was found to be 10% and 21%, respectively. Reduction in impact strength and density with increase in porosity was also reported with the addition of reinforcement. [ABSTRACT FROM AUTHOR]

This paper presents the results of a study into the production of the layered composite material. The basis of the composite material is high-alloy corrosion-resistant steel and nickel alloy 10Cr18Ni10Ti 06Cr15Ni60Mo15. A promising method of manufacture of such structures is the use of a multi-layer deposition. The use of highly concentrated heat sources to simplify the manufacture of such structures. A study of the technological possibilities of manufacturing laminates plasma arc of direct action of reverse polarity. Plasma arc reversed polarity allows for a minimum penetration or dissolution of the base metal to provide a bimetal with unique combinations of properties. The laminate structure of the composite material obtained by using light microscopy is researched. It is shown that the application of reverse polarity plasma arc current produces defect-free laminates in surfacing of steels and alloys of different classes. The surfacing has a fine structure with the uniform transition from one layer to the homogeneous material and a clear interface between dissimilar materials. The mechanical tests performed on the specimens have shown that the material has good mechanical properties. It combines such indicators as high tensile strength and maintaining a high yield strength and elongation of the resultant laminate is 22%. [ABSTRACT FROM AUTHOR]

Equal-channel angular pressing (ECAP) is a promising method for the processing of metals with an ultrafine-grain (UFG) structure of a few hundred nanometers in size. In this paper, the influence of solution treatment and artificial aging conditions, combined with a severe plastic deformation process on the AlMg3aluminum alloy, was studied. Samples were processed up to six passes with the application of processing route Bc, in which the sample after each separate pass is rotated clockwise by 90 degrees. Optical microscopy and electron backscattered diffraction were used to investigate the microstructure evolution at particular stages of the investigation. To estimate the effect of the process parameters on the change of the strength of the alloy, tensile properties and hardness measurements were determined. [ABSTRACT FROM PUBLISHER]

In this paper, the effects of Co addition on the microstructural evolution and mechanical properties of Ti-Nb based shape memory alloys were systematically studied. The results showed that the addition of Co into Ti-Nb shape memory alloy can tailor its average bond length of atoms and average d orbital energy level, further changing the phase constituents. With increasing Co content from 0.5 at.% to 5.0 at.%, the evolution of phase composition for Ti-Nb based shape memory alloys was as follows: α´´ + β → β + ω → β → α´´ + β → β. In contrast, the volume fraction of α´´ martensite phase in Ti-Nb shape memory alloys with 2.0 at.% Co was obviously higher than that in Ti-Nb shape memory alloys with 0.5 at.%. Moreover, the self-accommodation configuration with a V-shaped and triangular martensite variants were typical morphologies in Ti-Nb-Co shape memory alloy in order to the minimum energy theory. On the basis of solid solution strengthening, the yield strength and maximum tensile strength continuously increased, as the Co content is increased from 0.5 at.% to 3.0 at.%. However, the reduction of yield strength and maximum tensile strength was observed in Ti-Nb-Co shape memory alloy with 5.0 at.% Co owing to the formation of metastable β parent phase. Meanwhile, the largest value of micro-hardness (421 HV) can be optimized by tailoring 1.0 at.% Co as a result of solid solution strengthening and precipitation strengthening. • The phase composition of Ti-Nb-Co alloys with Co increasing is as follows: α´´ + β + →β + ω → β → α´´ + β → β. • The phase constitutes of Ti-Nb-Co can be tailored by changing Co content. • Co addition also has an effect on the grain size of Ti-Nb shape memory alloys. • A higher performance Ti-Nb-Co shape memory alloys with higher strength, good elongation and larger hardness can be obtained by tailoring Co contents. • The higher strength and larger recoverable strain can be achieved in Ti-Nb alloy with 3.0at.% Co. [ABSTRACT FROM AUTHOR]

The grind-hardening process utilizes the heat generated to induce martensitic phase transformation. However, the maximum achievable harden layer depth is limited due to high grinding forces, and the tensile residual stress appears on the ground surface in the grind-hardening process. This paper proposes a new grind-hardening technology using thermal compensation. The workpiece of AISI5140 steel is preheated by electric resistance heating, and ground under the condition of the workpiece temperature 25°C, 120°C, 180°C and 240°C. The grinding force, harden layer depth and surface quality including residual stress on ground surface, surface roughness and micro-hardness are investigated. The experimental results show that a deep harden layer with a fine grain martensite can be obtained with the thermal compensation. The ground workpiece surface produces a certain compressive residual stress, and the residual compressive stress value increases with preheating temperature. As the preheating temperature increases, grinding force slightly decreases, while there is slightly increment of surface roughness. Compared with the conventional grind-hardening process, both the harden layer depth and residual stress distribution are significantly improved. [ABSTRACT FROM AUTHOR]