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Friction stir welding (FSW) was introduced to join laser powder bed fusion (LPBF) AlSi10Mg alloys in this study. Microstructure and texture evolution, microhardness distribution and tensile properties of the FSW joints were investigated. The evolution of grain size, grain boundary and misorientation angles distribution, dynamic recrystallization and crystallographic texture in various regions of the FSW joint concerning base metal (BM), thermo-mechanically affected zone (TMAZ), upper part of nugget zone (UPNZ) and low part of nugget zone (LPNZ) was characterized by using electron back-scattered diffraction (EBSD). The analysis reveals a strong texture evolution of shear components on the TMAZ, UPNZ and LPNZ as well as a fully recrystallized grain structure on the UPNZ and LPNZ. Additionally, a gradual evolution in Si-rich eutectic from continuous cellular networks in the BM to totally globularized particles in the UPNZ and LPNZ occurs in the FSW joint. The microhardness rapidly decreases to the TMAZ from the BM through heat affected zone (HAZ) reaching the lowest value of ∼65.0 HV at the TMAZ/NZ boundary. The FSW joint in LPBF AlSi10Mg alloys exhibits an ultimate tensile strength (UTS) of 247 MPa and an elongation-to-failure (EI) of 8.8%. The UTS of FSW joints is reduced compared to the BM, but the EI has been increased by 160%, implying an improvement in tensile ductility. [Display omitted] • Friction stir welding was introduced to weld laser powder bed fusion AlSi10Mg. • New shear textures of F, R-Goss and R-Cube components are developed in the FSW joint. • LAGBs are increased in the TMAZ, and a high fraction of HAGBs is developed in the NZ. • FSW of LPBF AlSi10Mg results in a gradual evolution of Si-rich phase morphology in the joint. • FSW of LPBF AlSi10Mg produces the highest UTS of 247.0 MPa and the maximum EI of 8.8%. [ABSTRACT FROM AUTHOR]

Titanium-tantalum (Ti-Ta) alloy has excellent biomechanical properties with high strength and low Young's modulus, showing great application potential in the biomedical industry. In this study, Ti-Ta alloy samples were prepared by laser powder bed fusion (LPBF) technology with mixed pure 75 wt.% Ti and 25 wt.% Ta powders as the feedstock. The maximum relative density of Ti-Ta samples prepared by LPBF reached 99.9%. It is well-accepted that four nonequilibrium phases, namely, α′, α″ and metastable β phase exist in Ti-Ta alloys. The structure of α′, α″ and β are hexagonal close-packed (HCP), base-centered orthorhombic (BCO) and body-centered cubic (BCC), respectively. X-ray Diffraction (XRD) analysis showed that the α′ phase transformed to the α″ phase with the increase of energy density. The lamellar α′/α″ phases and the α″ twins were generated in the prior β phase. The microstructure and mechanical properties of the Ti-Ta alloy were optimized with different LPBF processing parameters. The samples prepared by LPBF energy density of 381 J/mm3 had a favorable ultimate strength (UTS) of 1076 ± 2 MPa and yield strength of 795 ± 16 MPa. The samples prepared by LPBF energy density of 76 had excellent ductility, with an elongation of 31% at fracture. [ABSTRACT FROM AUTHOR]

The additive manufacturing (AM) 3D printing technique is the most feasible, advanced technology for metal parts that have attracted great attention in the manufacturing industry. AM of titanium alloys by selective laser melting (SLM) is one of the most recent research developments in this field because of its benefits and wide applicability in manufacturing sectors. SLM is an efficient, convenient AM technology that can quickly form complex structures. A well-known titanium alloy named Ti6Al4V, manufactured by SLM, has several practical applications in engineering technology, including cars, space shuttles, and aeronautics. This paper demonstrates the density, sectional morphology, microstructure, and mechanical properties before and after heat treatment of Ti6Al4V alloy sample due to laser power, exposure time, and line spacing. A selective laser melting technology was used to fabricate the Ti6Al4V samples. The results show that the sample defects decreased with the increase in laser power. Moreover, when the laser power was 400 W combined with an exposure time of 30 µs, the sample's tensile strength reached 1203 MPa, almost 300MPa greater than that of ordinary forged Ti6Al4V titanium alloy after annealing. The continuous variation in the line spacing within a certain limit (50-65 µm) could increase the relative density up to 99.59%, which is much better than previously reported results. The tensile fracture of the sample presents a brittle crack. [ABSTRACT FROM AUTHOR]

Zinc (Zn) alloys have recently revolutionized and shown promising usage for degradable biomedical implants (BMI). However, due to the low strength of pure Zn, its application in the biomedical industry was limited. In the current research, an innovative biodegradable Zn-0.4Li-0.4Cu alloy produced by laser powder bed fusion (LPBF) with good mechanical properties was investigated. The Zn-0.4Li-0.4Cu alloy showed superior mechanical properties (tensile strength at 296 MPa, yield strength at 260 MPa, and after heat treatment elongation at 8.3 %), a record for biodegradable Zn alloys, as a consequence of grain refinement, second-phase precipitation of intermetallic compounds, and solid solution strengthening. The impacts of Cu and Li on the microstructures, mechanical behaviors, corrosive behavior and deterioration rate of the Zn-0.4Li-0.4Cu alloy were studied. The addition of Cu and inherent fast-cooling rate of the LPBF process are favorable for promoting the nucleation events, leading to the refinement of grains. In addition, the formation of the second-phase precipitates (CuZn 4 and ZnLi 4) in the matrix was founded to further improve the mechanical properties. Moreover, the alloy showed a consistent degradation manner and a suitable degradation rate of 0.023 mm/year. Based on the findings shown above, the biodegradable Zn-0.4Li-0.4Cu alloy can be a potential candidate for vascular stents and medical applications due to its excellent mechanical properties and adequate degrading behavior. • The Zn-0.4Li-0.4Cu alloy produced by laser powder bed fusion (LPBF) demonstrated exceptional mechanical properties, with a tensile strength greater than 296 MPa, and elongation of 8.3 %. • The superior mechanical properties of the as-LPBF-built Zn-0.4Li-0.4Cu alloy can be attributed to the morphology and distribution of the intermetallic compounds and dislocations. • The novel biodegradable Zn-0.4Li-0.4Cu alloy is a promising candidate for fabricating degradable biomedical implants due to its strength, reasonable ductility, and satisfactory degradation rate. [ABSTRACT FROM AUTHOR]

A dense Cu-10Sn alloy bulk specimen was obtained by optimizing the laser powder bed fusion (L-PBF) processing, and the relative density of the specimen reached 99.7%. The grain morphology was mainly the columnar dendrite and inter-dendritic phases generated along the solidification direction. Tensile testing and detailed microstructural characterization were carried out on specimens in the as-built and heat-treated condition. Under the quasi-static tensile condition, the yield strength (σ0.2), ultimate tensile strength (UTS), and the elongation of the as-built Cu-10Sn specimen were 392 MPa, 749 MPa and 29%, respectively. After the solution treatment at 800 °C for 4 h, and aging treatment at 400 °C for 2 hours, the microstructure of the specimen transformed from the columnar grain to equiaxed grain, the dislocation density decrease, and numerous annealing twins were observed in the heat-treated state. Therefore, the quasi-static tensile yield strength (σ0.2) of the specimen was reduced to 245 MPa. However, the UTS and the elongation were increased to 840 MPa and 56%, respectively, due to the interaction between annealing twins and equiaxed grain. [ABSTRACT FROM AUTHOR]

Purpose: In this research, the highly dense bulk Cu-5Sn alloy specimens were fabricated using selective laser melting (SLM). This study aims to establish the relationship between laser power (LP), scanning speed (SS) and hatch space (HS) with surface roughness (Ra) and density. To obtain Cu-5Sn alloy formed parts with high strength and low surface roughness. The microstructure and mechanical properties of SLMed Cu-5Sn were investigated. Design/methodology/approach: The relative density (RD) was optimized using the response surface method (RSM) and analysis of variance. First, the Ra of SLMed formed specimens was studied to optimize the forming process parameters with a good surface. Then, the dense specimens were studied by ANOVA and the RSM to obtain dense specimens for mechanical property analysis. Findings: Dense specimens were obtained by RSM and ANOVA. The tensile properties were compared with the casted specimens. The yield and ultimate strengths increased from 71 and 131 MPa for the cast specimens to 334 and 489 MPa for the SLMed specimens, respectively. The ductility increased significantly from 11% to 23%, due to the refined microstructure of the SLMed specimens, as well as the formation of many twin crystals. Originality/value: The Ra, RD and mechanical properties of SLM specimens Cu-5Sn were systematically studied, and the influencing factors were analyzed together. This study provides a theoretical and practical example to improve the surface quality and RD. [ABSTRACT FROM AUTHOR]

• Mo-10Si-(0, 5, 10, 15)B (at.%) alloys were prepared by vacuum arc-melting technique. • The effect of B content on phase constitution was discussed and the microstructure evolution was illustrated. • The relationship between the microstructure of the alloys and the mechanical properties was established. • The oxidation resistance of the alloys was evaluated and the mechanism of oxidation resistance was studied. The Mo-10Si-(0, 5, 10, 15)B (at.%) alloys located in Mo ss (Mo solid solution) +Mo 3 Si +T2 (Mo 5 SiB 2) region were prepared by arc melting. The effect of B content on the microstructure, microhardness, fracture toughness and oxidation resistance of the alloys was studied. In the Mo-10Si alloy, there are primary Mo ss and peritectic Mo 3 Si phases. With the addition of B, (Mo ss + T2) binary and (Mo ss + T2 + Mo 3 Si) ternary eutectics emerge in Mo-10Si-(5, 10)B alloys. For Mo-10Si-15B alloy, primary Mo ss disappears and the microstructure is only composed of binary and ternary eutectics. With the increase of B content, the proportion and grain size of Mo ss decrease. The microhardness of alloys increases with the increase of B content due to the increasing intermetallics. The fracture toughness of alloys decreases obviously in single-edge notched three-point bending testing (SENB) and the fracture mode transforms from transgranular fracture to intergranular fracture because of the refinement of Mo ss. In the high-temperature oxidation test at 1250 °C, the oxidation weight loss of the alloys decreases with the addition of B due to the densification of the borosilicate layer. [ABSTRACT FROM AUTHOR]

To obtain compatible properties of low thermal conductivity and high thermal stability, Al 0.6 CoCrFeNiTi high-entropy alloy was designed as a novel candidate of metal-based thermal barrier coatings (MBTBCs). The corresponding high-entropy alloy coatings were fabricated by both high-velocity oxygen-fuel spraying (HVOF) and atmospheric plasma spraying (APS), and then the dependence of thermal insulation properties on microstructure was investigated. The both coatings exhibit a simple body-centered cubic (BCC) structure, but present obvious difference in microstructure and defect characters which relates to the evolution of in-flight particles. Benefit from the extremely low thermal conductivity, the APS-deposited coating can increase 13.24 °C of the surface temperature of piston crown and yield a temperature reduction of 19.00 °C along the thickness direction, which mean a positivity on enhancing the power efficiency of vehicle engines without sacrificing the strength of aluminum alloy components. In virtue of a decoupling method, the crucial effect of microstructure on thermal conductivity is disclosed, thus interpreting the excellent thermal insulation property of APS-deposited coating dominated by grain refinement and disordered BCC structure. The present results demonstrate a great potential of high-entropy alloy coatings as thermal barrier application and provide an inspiration for future works aiming to design these coatings to meet specific engineering needs. • High-entropy alloys were firstly proposed to perform a candidate of metal-based thermal barrier coatings. • Low thermal conductivity and high thermal stability were balanced in APS-deposited Al 0.6 CoCrFeNiTi coating. • The application of Al 0.6 CoCrFeNiTi coating enhanced power efficiency and protected aluminum alloy pistons. • The thermal insulation properties depended on microstructure including grain size and atomic arrangement. [ABSTRACT FROM AUTHOR]

Abstract Cu-10Sn alloy with body-center-cubic (BCC) lattice structure was fabricated through selective laser melting (SLM). The geometry of SLMed BCC lattice Cu-10Sn alloy (rod diammeter ∼300 μm, length ∼700 μm) was in good agreement with the design model. Similar with the nearly full density Cu-10Sn alloy, columnar also constituted the majority parts of the lattice structure Cu-10Sn, but exhibited various morphologies due to the different grain growth orientation under thermal effect. The gowth orientation of columnar grain in the rods oriented to the as-fabricated layer due to the higher thermal conductivity of the as-fabricated layers. Graphical abstract Image 1 Highlights • Cu-10Sn alloy with BCC lattice structure was fabricated through SLM. • The geometry of BCC lattice Cu-10Sn alloy was in good agreement with the design model. • The BCC lattice Cu-10Sn exhibited various grain morphologies under thermal effect. • The gowth orientation of columnar grain in the rods oriented to the as-fabricated layer. [ABSTRACT FROM AUTHOR]

Herein, different heat treatment protocols are adopted to further improve the mechanical properties of the Al–Cr–Fe–Ni–V high-entropy alloy (HEA) fabricated by laser powder bed fusion (LPBF) additive manufacturing (AM). The initial LPBF-processed HEA rendered a combination of high strength (ultimate tensile strength (UTS) of 810.93 MPa) and ductility (fracture elongation (FE) of 35.43%), which could be attributed to the hierarchical microstructure with fine grains, cellular dislocation structure, and L1 2 nano-precipitation. When the annealing temperature is increased from 573 K to 1473 K, the cellular dislocation structure is disappeared, and both L1 2 and B2 phases are progressively precipitated in the FCC matrix. Simultaneously, the tensile strength dramatically increased at the expense of ductility reduced and LPBF-processed HEA demonstrated a high UTS of 1192.84 MPa and FE of 15.32% after annealing at 1173 K. The results reveal that precipitation strengthening plays a significant role in improving the mechanical properties of LPBF-processed HEAs during annealing. For instance, L1 2 and B2 precipitates hindered the dislocation movement and, in turn, enhanced the pinning force of boundary migration. Moreover, the highly coherent and low misfit FCC-L1 2 interfaces minimized the strain accumulation due to the dislocation shear and, thereby, prevented the crack initiation. [ABSTRACT FROM AUTHOR]