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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 microstructure of LPBF-NiTi alloy was regulated by switching the heat transfer mode. • The grain morphology of LPBF-NiTi alloy exhibited fine grain at the conduction mode. • The grain morphology of LPBF-NiTi alloy exhibited coarse grain at the keyhole mode. The function-graded NiTi part is one of the greatest potential smart materials due to its superelasticity, shape memory, biocompatibility and the ability of coupling complex functionality. Laser powder bed fusion (LPBF) is a promising method for the preparation of microstructure-gradient NiTi parts. The microstructure of the NiTi alloy prepared by LPBF was tailored by switching the heat transfer modes through the variation of the process parameters. The LPBF-fabricated NiTi alloy with fine grains is obtained in the conduction mode because the laser energy is enough to melt the powder while, the growth of the grains is restricted without enough power. In comparison, the coarse grains penetrating through two or more layers is obtained in the keyhole mode, due to the appearance of the keyholes reheating the previous layers. This work proved the feasibility for the preparation of microstructure-gradient NiTi alloys by LPBF. [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]

In this study, newly developed NiCrB and conventional NiCrTi coatings were produced by arc spraying using compressed air and nitrogen as atomization gases. In this way, four coatings with different oxide contents were produced. The coatings were investigated in terms of their phase compositions, oxygen contents, and microstructures. The results showed that the oxygen contents in coatings were pronouncedly reduced by nitrogen-atomized compared to air-atomized. The oxygen contents in the nitrogen-atomized coatings were about one-fourth of those in the corresponding air-atomized coatings, respectively. No significant oxide phases were observed in the XRD patterns of the nitrogen-atomized coatings. Moreover, the corrosion behavior of the coatings was studied using a hot corrosion test in molten Na2SO4-10 wt.% NaCl salt at T = 800 °C. All coatings were significantly corroded under this test condition. However, NiCrB coatings exhibited higher corrosion resistance than NiCrTi coatings. The NiCrB and NiCrTi coatings prepared by nitrogen atomization corroded more severely in the initial stage than the corresponding coatings prepared by air atomization. The NiCrB coating with air-atomized showed the best corrosion resistance due to the low chromium content and the addition of boron. [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]

In this study, a laser remelting process was applied to the FeCrCoNiTiAl0.6 high entropy alloy coating in order to improve the density and the surface quality of the coating. The coating was fabricated by high-velocity-oxygen-fuel (HVOF) technology. The microstructure and phase composition of the coating were investigated by scanning electron microscopy (SEM), energy dispersive X-ray spectrometer (EDS), X-ray diffractometer (XRD) and confocal scanning laser microscope (CSLM). Moreover, the wear behavior of the coating was evaluated by use of a ball-on-disc test. The coating was denser after laser remelting treatment by eliminating the previous lamellar structure. The microstructure of the laser-remelted coating exhibits two body-centered cubic (BCC) phases, which is different from the HVOF coating. In addition, aluminum oxide formed during laser remelting. Different from the wear mechanism of the HVOF coating, which comprised abrasion and fatigue, the major wear of the laser remelted coating was abrasion. [ABSTRACT FROM AUTHOR]

Hydroxyapatite (HA) is widely used as surface coatings on biomedical metal implants because of its excellent biocompatibility and osteoconductivity. In this study, HA coatings were deposited onto Ti-6Al-4V substrates by micro-plasma spraying and then heat treated at 650 °C in a muffle furnace for 3 h and 6 h. XRD results showed that, the HA peaks were sharper than those of corresponding as-sprayed coatings and the amorphous diffuse background was reduced after heat treatment. The transformation from impurity phases such as tetra-calcium phosphate (TTCP) and tri-calcium phosphate (TCP) and amorphous calcium phosphate (ACP) to crystalline HA occurred during the heat treatment. Moreover, the texture intensity was not increased during the re-crystallization of ACP and the transformation of impurity phases into HA. The SEM results showed that nanograins were formed on the coating surface. In addition, with the increase of the holding time, the nanograins become coarse. • Three kinds of HA coatings with different phase structure were fabricated by micro-plasma spraying. • The effect of heat treatment on the crystallinity, microstructure and surface morphology of HA coatings was investigated. • After heat treatment, nanograins of HA were formed on the coating surface and the nanograins became coarse with the increase of the holding time. [ABSTRACT FROM AUTHOR]

Si-rich Mo-Si-B powders (Mo-62Si-5B at%) were deposited on Nb-Si based alloy by laser cladding assisted with ultrasonic vibration. The obtained coatings mainly consist of MoSi 2 and (Mo, X) 5 Si 3 (X = Nb and Ti). With the introduction of ultrasonic vibration during laser cladding, the lath-shaped MoSi 2 phase transforms into cellular gradually. Meanwhile, the discrepancy on the microstructure of the top region and the bottom region is eliminated gradually, indicating that the cavitation and acoustic streaming of ultrasonic vibration not only refines the microstructure, but also homogenizes the element and phase distribution in the coatings. High-temperature oxidation experiment at 1250 ℃ were conducted to assess the oxidation resistance of the coatings. Compared with Nb-Si alloy, the coated specimens have much lower oxidation weight increase. Furthermore, with the assistance of ultrasonic vibration, the oxidation resistance of the coating is enhanced further. The oxide scales on the coatings consist of two layers: an upper amorphous aluminoborosilica with TiO 2 particles dispersed and a lower crystalline SiO 2 layer. With the introduction of ultrasonic vibration, the microstructure of the coatings is refined, resulting in more phase and grain boundaries in the coatings. Therefore, the diffusion of the elements to the surface is accelerated and the protective oxide scale can be formed quickly. • Si-rich Mo-Si-B coatings were prepared on Nb-Si based alloy by laser cladding assisted with ultrasonic vibration. • The ultrasonic vibration refines the microstructure and homogenizes the phase distribution in the coatings. • The oxide scale on the coatings consists of an upper amorphous aluminoborosilica and a lower crystalline SiO 2 layer. • The ultrasonic vibration improves the oxidation resistance of the coatings because of more phase and grain boundaries. [ABSTRACT FROM AUTHOR]

W-based composites with the different immiscible second phases (Cu and Cu10Sn) were prepared by laser powder bed fusion (LPBF). The immiscible W phase and Cu/α-Cu phases were prone to separate during LPBF. The melted W phase could easily fuse together and form W matrix, and Cu or α-Cu phase distributed within the gaps among W phase. Cu or α-Cu phase can provide a gradient cooling way for the solidification of W phase through the transformation of 'solid-liquid-gas' during LPBF. The evaporation of Cu or Sn accelerated the heat dissipation, which caused the grain refinement of W. Higher thermal conductivity of Cu than α-Cu leads to the relative finer grain size of W phase in W-Cu composite. The heat conduction direction between W phase and Cu/α-Cu also affected the grain morphology. Heat continued transferred from W to Cu/α-Cu induced the columnar grain growth of W, the interlacing distribution of W and Cu/α-Cu made the growth of W columnar grains radiate out from the center Cu/α-Cu phase. Remarkable, cracks were severely restrained in W phase simultaneously although W phase melted completely. This is not only related to improvement of strength and ductility of W caused by grain refinement, but also because of the interlacing distribution of W and Cu/α-Cu phases, which could effectively reduce the stress degree in W phase during LBPF. [Display omitted] • W-Cu and W-Cu10Sn composites with free crack were successfully prepared by LPBF. • W phase formed skeleton structure in both W-Cu and W-Cu10Sn composites. • The addition of Cu/ Cu10Sn induced the grain refinement of W phase. [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]

Pure Copper (Cu) is very difficult to prepare using selective laser melting (SLM) technology. This work successfully prepared the pure Cu with high relative density and high strength by the SLM technology using a surface oxidation treatment. The gas-atomized pure Cu powder was used as the feedstock in this work. Before the SLM process, the pure Cu powder was initially handled using the surface oxidation treatment to coat the powder with an extremely thin layer of Cu2O. The SLMed highly dense specimens contain α-Cu and nano-Cu2O phases. A relationship between the processing parameters (laser power (LP), scanning speed (SS), and hatch space (HS)) and density of Cu alloy in SLM was also investigated. The microstructure of SLMed Cu consists of fine grains with grain sizes ranging from 0.5 to ~30 μm. Tensile testing and detailed microstructural characterization were performed on specimens in the as-SLMed and pure copper state specimens. The mechanical property experiments showed that the specimens prepared by SLM technology containing nano-oxide phases had higher yield strength and tensile strength than that of other SLM-built pure copper. However, the elongation was remarkably decreased compared to other SLM-built pure copper, due to the fine grains and the nano-oxides. [ABSTRACT FROM AUTHOR]

• A new method of non-contact ultrasonic-assisted laser metal deposition was used to perform laser deposition of Fe-based powder with 42CrMoA substrate. • The effects of ultrasonic amplitude (UA) and excitation distance (d) on the depth width of deposition layer, columnar crystal length, grain size and distribution, and mechanical properties were studied. • Due to the cavitation effect of ultrasonic, it effectively refines the grains and promotes the columnar to equiaxed transition (CET) of grains at the interface. Meanwhile, the cracks generated in the deposition layer can be effectively inhibited and the mechanical properties can be improved. • The application of ultrasonic-assisted can effectively improve the mechanical properties of the deposition layer, and the uniformity of mechanical properties is improved. In order to study the effects of ultrasonic parameters on the microstructure and mechanical properties of non-contact ultrasonic assisted laser deposition, Fe-based powder was deposited on 42CrMoA steels with different ultrasonic amplitudes (UA) and excitation distances (d). The results show that the ultrasonic-assisted laser metal deposition (LMD) of Fe-based powder increases depth and width of the deposition layers. Due to the cavitation effect of ultrasonic, it effectively refines the grains and promotes the columnar to equiaxed transition (CET) of grains at the interface. When d = 50 mm, the grain size greater than 8 μm accounts for only 3.1 %, but the ultrasonic vibrations haven't changed the phase type of the structures. With ultrasonic-assisted, the cracks generated in the deposition layer can be effectively inhibited and the mechanical properties can be improved. When d = 80 mm and UA = 30 μm, the average microhardness of the deposition layer reaches 772.9 HV, which is 95.8 HV higher than that without ultrasonic-assisted deposition. When UA = 40 μm, the tensile strength is 1237.9 MPa, which is increased by 26.8 % compared to without ultrasonic-assisted deposition. Compared to without ultrasonic-assisted, the friction coefficient of deposition layers is significantly decreased by 25.5 % with the application of UA = 30 μm. [ABSTRACT FROM AUTHOR]

High-entropy alloys exhibit some interesting mechanical properties including an excellent resistance against softening at elevated temperatures. This gives high-entropy alloys (HEAs) great potential as new structural materials for high-temperature applications. In a previous study of the authors, oxidation behavior of Al0.6CrFeCoNi and Al0.6CrFeCoNiSi0.3 high-entropy alloys at T = 800 °C, 900 °C and 1000 °C was investigated. Si-alloying was found to increase the oxidation resistance by promoting the formation of a continuous Al2O3 layer, avoiding the formation of AlN at T = 800 °C. Obvious phase changes were identified in the surface areas of both alloys after the oxidation experiments. However, the effects of heat treatment and Si-alloying on the phase transition in the bulk were not investigated yet. In this study, Al0.6CrFeCoNi and Al0.6CrFeCoNiSi0.3 high-entropy alloys were heat-treated at T = 800 °C and T = 1000 °C to investigate the effect of heat treatment on microstructure, phase composition and mechanical properties of both alloys. The results show that alloying Al0.6CrFeCoNi with Si caused a phase transition from dual phases consisting of BCC and FCC to a single BCC phase in an as-cast condition. Furthermore, increased hardness for as-cast and heat-treated samples compared with the Al0.6CrFeCoNi alloy was observed. In addition, the heat treatment facilitated the phase transition and the precipitation of the intermetallic phase, which resulted in the change of the mechanical properties of the alloys. [ABSTRACT FROM AUTHOR]

Abstract: A series of Fe–xCr cored wires (x =15, 20, 25, 30, 35 and 40% in weight) were used to produce protective coatings for components used in high-temperature environments by wire-arc spraying. The microstructure, morphology and high-temperature oxidation behavior of the Fe–xCr coatings were investigated. The Fe–xCr coatings presented a homogeneous structure with thin oxide inclusions and low porosity. Thermogravimetric analysis was used to evaluate the high-temperature oxidation behavior of the coatings at a temperature of 650°C under cyclic oxidation conditions. The results showed that all the Fe–xCr coatings exhibited significantly lower weight gain than the uncoated substrate. As Cr content of the coatings increased, the thickness of oxide scales decreased and oxidation resistance improved. [Copyright &y& Elsevier]

Abstract: Butt joints of 3.0mm thick sheets of an Al–Li based alloy have been produced using Nd:YAG laser welding without filler metals. The hardness distribution and microstructure of the alloy and welded joints were investigated. The changes in the grain shapes, grain orientations, microtexture, and precipitates of the fusion zone were analyzed using optical microscope, electron back scattered diffraction (EBSD) and transmission electron microscopy (TEM). The results show that Nd:YAG laser welding leads to a change of the microhardness, grain shape, grain orientations, and a disappearance of the microtexture and precipitates. A narrow band of EQZ along the fusion boundary and a predominantly equiaxed dendritic structure are developed in the fusion zone. The formation of the predominately equiaxed dendritic grains is due to a heterogeneous nucleation mechanism aided by equilibrium A13Zr phases as well as the growth of pre-existing nuclei created by dendrite fragmentation, or by grain detachment resulted from Nd:YAG laser welding processes. In addition, Nd:YAG laser welding produces lower Vickers hardness than that of the base metal due to the decrease in the in quantity of δ′ precipitates in the fusion zone. [Copyright &y& Elsevier]

Almost fully dense AlCrFeNiV HEA consisting of face-centred-cubic (FCC) solid solution and L1 2 nano phase was prepared from gas-atomized alloy powder with optimized selective laser melting (SLM) processing parameters. Microstructure characterization reveals the presence of hierarchical structures including columnar grains, sub-grains, L1 2 nano phase and dislocations in SLMed HEA. Unique columnar grains ranging from several tens of microns up to 200 μm grow along the direction of the temperature gradient. High cooling speed and non-equilibrium solidification during SLM process induced the formation of sub-grains in every columnar grain, accompanied with the heterogeneous distribution of dislocations and L1 2 nano phase. The SLMed AlCrFeNiV HEA exhibited an outstanding combination of high strength (ultimate tensile strength ∼1057.47 MPa) and excellent ductility (plastic strain ∼30.3%). The characteristic hierarchically heterogeneous structure contributes to the increase of strength without losing ductility. The sub-grains contribute significantly to the enhanced strength through dislocation hardening. The excellent ductility is correlated with the progressive work-hardening mechanism regulated by the heterogeneous distribution dislocation and L1 2 nano phase within sub-grains. Image 1 • Almost fully dense AlCrFeNiV HEA was fabricated by SLM. • SLMed HEA consists of FCC phase and L1 2 nano phase. • SLMed HEA shows hierarchically heterogeneous microstructure. • SLMed HEA exhibits high ultimate tensile strength of 1057.47 MPa and plasticity of 30.3%. [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 For the aim of thermal barrier application in vehicle engines, a specific FeCrNbBSiC cored wire of consideration was produced to fabricate amorphous coating by wire-arc spraying. The microstructure and thermal conductivity of the as-deposited coating were characterized in detail. The results show that the FeCrNbBSiC coating (FB coating) primarily consists of amorphous phase owing to the combination of proper composition design and rapid quenching of wire-arc spraying. However, a fraction of crystalline phases coexists with the amorphous matrix, due to the both effects of partially incomplete alloying and continuous annealing. Depending on the expected amorphous structure, thermal conductivity of the developed FB coating is as low as 2.15 W/mK at room temperature, almost half of the referenced 316L stainless steel coating (SS coating, 4.20 W/mK), and displays relatively slow and limited increase with elevated temperature up to 500 °C. By means of temperature distribution analysis, an obviously higher temperature is found on the top surface of FB coating covered piston, which implies a benefit of enhancing heat energy conversion. Simultaneously, the temperature of aluminium alloy substrate could also be reduced by covered coating as the role of thermal insulation. Therefore, the wire-arc sprayed FeCrNbBSiC amorphous coating developed here with excellent thermal barrier performance and economic advantage could be a promising innovation and candidate for metal-based thermal barrier coatings applied in vehicle engines. Highlights • Innovative scheme of metal-based thermal barrier coatings was designed. • Wire-arc sprayed FeCrNbBSiC amorphous coating with high T x was obtained. • Incomplete alloying and continuous annealing result in crystalline phases formed. • Amorphization endows excellent thermal barrier ability for this coating (κ = 2.15 W/mK). • Application of this coating improves power efficiency and protects substrate effectively. [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]

Abstract In this study, an Al 0.6 TiCrFeCoNi high entropy alloy coating was produced by high-velocity-oxygen-fuel spraying. The microstructure and phase composition of the coating were investigated, moreover the hardness and the fracture toughness of the coating were determined. The wear behavior of the coating at different temperatures was evaluated using a pin-on-disc test. The results show that the coating was very dense and consisted of lamellae. Two BCC phases with similar lattice parameters were detected in the as-sprayed coating. The wear of the coating against an Al 2 O 3 counter body was mainly caused by abrasion at all temperatures. The role of fatigue wear increased with increasing test temperature. In addition, tribo-reaction played an important role at the test temperature of T = 500 °C, which led to the lowest friction coefficient of the coating under the given test conditions. Highlights • The wear behavior of Al 0.6 TiCrFeCoNi HVOF coating was investigated at room temperature, T=300°C and T=500°C in detail. • The wear behavior of the coating changed significantly with the increasing test temperatures. • The wear behavior of the coating changed significantly with the increasing test temperatures. • The wear mechanism changed with temperatures, tribo-reaction played an important role at test temperature of T=500°C. [ABSTRACT FROM AUTHOR]

Laser welding of Q235 low carbon steel and 6061 aluminum (Al) alloy was carried out by using a dual beam fiber laser in keyhole welding mode in a steel-on-Al lapped configuration. The influence of processing parameters of power distribution ratios ( R s ) and dual beam laser distances ( d 1 ) on the weld shapes, microstructures of intermetallic compound (IMC) layers, microhardness and tensile resistance of the steel/Al joints was studied. Soundly welded steel/Al joints have been achieved by using dual beam laser keyhole welding at R s   = 0.67 and d 1  = 1.5 mm. The key factor affecting welding defects is the control of the penetration depth of the welds, and good weld shape has been achieved when the penetration depth of the welds is below 700 m. The formation of IMC phases consisted of Fe 4 Al 13 , Fe 2 Al 5 and FeAl 2 phases is only limited to the weld/Al interface when the steel/Al joint has a relatively low penetration depth of the welds in the steel/Al joint. The maximum tensile resistance of the steel/Al alloy joints of 115.6 N/mm is obtained under the conditions of R s  = 0.67 and d 1  = 1.5 mm. The fracture surface reveals a mixed failure occurred in the Al alloy leading to high tensile resistance of the steel/Al joints. [ABSTRACT FROM AUTHOR]