Solid-solution Strengthening Effect Research Articles

Surface microstructures and properties of oxide-reinforced FeCrAl matrix composite coatings prepared by laser cladding on a ferritic-martensitic steel

In this work, two oxide-reinforced FeCrAl matrix composite coatings, FeCrAl-Al2O3 and FeCrAl-Y2O3, were fabricated on a ferritic-martensitic steel by laser cladding with their microstructures probed by means of multiple characterization methods. Their cross-sections are found to consist of three zones with distinct microstructure features, i.e. cladding zone (CZ), heat-affected zone (HAZ) and substrate. Their CZs are mainly composed of columnar ferrite (the average grain sizes 7.1 ± 3.9 µm and 6.5 ± 3.8 µm for the FeCrAl-Al2O3 and the FeCrAl-Y2O3 coatings, respectively), with plenty of O-rich particles dispersed inside the ferrite. For the HAZs, they are essentially comprised of markedly refined martensitic laths. The average surface hardnesses of the FeCrAl-Al2O3 and the FeCrAl-Y2O3 coatings are 357.1 ± 8.7 HV and 348.4 ± 26.1 HV, respectively, notably higher than the substrate (264.7 ± 2.7 HV). Such effective hardening is attributed to the combined effect of solid-solution and dispersion strengthening. The wear rates of the FeCrAl-Al2O3 and the FeCrAl-Y2O3 coatings are 37% and 73% lower than the substrate, respectively, demonstrating considerably enhanced wear resistance. After characterizing the worn surfaces, abrasive wear and oxidative wear are confirmed to occur on all the specimens during the wear test. The enhanced wear resistance of both the composite coatings should mainly be related to the high hardnesses produced by their specific microstructural features, and the easier formation of surface oxide films during the wear.

Enhanced thermal stability and mechanical properties of the nanocrystalline multicomponent Fe–(ZrNbMoTa)x alloys

Thermal stability and mechanical property of the multicomponent nanocrystalline Fe–ZrNbMoTa alloys were investigated. Single-phase nanocrystalline Fe–(ZrNbMoTa)x (x = 0.1, 0.2, 0.5 and 1 at. %) alloys were prepared by ball milling and followed by annealing in a set of predesigned condition. It was found that the Fe-based multicomponent alloys possess good thermal stability through 10 h annealing at 900 °C, which is attributed to the thermodynamics effect in the reduction of grain boundary energy caused by multicomponent co-segregation of Zr, Nb, Mo and Ta, and kinetics effect related to sluggish diffusion and Zener pinning of a small amount of second-phase precipitation. Additionally, nanocrystalline Fe–(ZrNbMoTa)x alloys show excellent mechanical properties. The hardness is 738.6 HV, and its yield strength and compressive strength reach up to 3100 MPa and 3600 MPa, respectively. These are attributed to the comprehensive effects of nanocrystalline, solid solution and second phase strengthening.

Effects of atomic size misfit on dislocation mobility in FCC dense solid solution: Atomic simulations and phenomenological modeling

Understanding the interactions between solute atoms and dislocations is essential to developing metallic materials for simultaneously high strength and ductility. Previous studies have majorly focused on the temperature and solute concentration effects on these interactions, excluding the solute atomic size effect; this greatly limits the capacity of design and strength prediction of alloys. In this study, the effects of atomic size misfit on edge dislocation mobility in model random FCC solid solution alloys are investigated by molecular dynamics (MD) simulations. Our results show that dislocation mobilities are atomic size misfit-dependent only when they are larger than a critical value. Additionally, when the atomic size misfit is greater than the critical value, the dislocation motion is controlled by the pinning mechanism. Conversely, when the atomic size misfit is lower than the critical value, the dislocation mobility is unaffected by the solute atoms because of the negligible lattice distortion, however, it is dominated by the phonon drag mechanism as observed in the pure elemental metal. Thus, the drag coefficient, which reflects the dislocation mobility, exhibits different temperature dependences. Based on these observations, a piecewise linear fit relation of the drag coefficient as a function of atomic size misfit and temperature is determined. Finally, the phenomenological dislocation mobility model containing the atomic size misfit and temperature is established. The results can serve to enhance the understanding of solid-solution strengthening effect. The mobility law that derived from the atomic scale can enable accurate DDD simulations at the mesoscale.

Effects of Simulated PWHT on the Microstructure and Mechanical Properties of 2.25Cr1Mo0.25V Steel for a Hydrogenation Reactor

The effect of post-welding heat treatment (PWHT) on the microstructure and mechanical properties of large-thickness 2.25Cr1Mo0.25V steel was investigated through simulated post-welding heat treatment (SPWHT). The results showed that an increase in the SPWHT time decreased the toughness, hardness, and strength of the steel. After Min.SPWHT, the high-temperature tensile strength decreased more significantly, and the damage of Min.SPWHT to the high-temperature tensile strength reached approximately 80% of the Max.SPWHT. The microstructure of the tested steel before and after SPWHT consisted of granular bainite and lath bainite. After SPWHT, intergranular carbides were precipitated as coarsened carbides, carbide clusters, and chains of carbides; alloy element segregation occurred, and the segregation of Mo was the most serious, followed by Cr, and V. The precipitation behavior of the carbides and the increase in the effective grain size caused by the widening of the bainite–ferrite lath worked together and resulted in the decline of the impact toughness; the reduction in the solid solution and precipitation strengthening effects were the main factors in the strength reduction of the tested steel. In the high-temperature tensile tests, defects first appeared around the coarse carbides and carbide clusters. Controlling the size of the intergranular large-size carbides and the degree of cluster precipitation in the NT state structure may be a means of obtaining higher strength of the base metal subjected to PWHT.

Effective combination of solid solution strengthening and precipitation hardening in NiCrFeWTiAl multi-principal element alloys

Face-centered-cubic (FCC) Multi-principal element alloys (MPEAs) have attracted intensive scientific research interest due to their excellent fracture toughness and ductility. Still, the strengths of single-phase MPEAs are unsatisfactory. Although great progress has been made by utilizing multiple strengthening mechanisms, it remains challenging to take advantage of large-atom solutes and nano-precipitates simultaneously because solutes always partition into the precipitates. In the present work, we successfully achieved an effective combination of solid solution strengthening and precipitation hardening in the NiCrFeWTiAl multi-principal element alloys. Our experimental results showed that W is partitioned into the FCC matrix, while Ti and Al tend to exist in the L12 phase. This controlled elemental partitioning leads to a good combination of solid solution strengthening and precipitation hardening effects and results in good tensile properties at temperatures from 25 ℃ to 760 ℃. The strengthening mechanisms were revealed based on the quantified microstructure analysis. The solid solution hardening of all the solute atoms contributes ∼140 MPa in total, but W mainly contributes to solid solution hardening, and L12 precipitates enhance the yield strength by ∼330 MPa through ordering strengthening.

Microstructure and strengthening mechanisms of novel lightweight TiAlV0.5CrMo refractory high-entropy alloy fabricated by mechanical alloying and spark plasma sintering

Lightweight TiAlV0.5CrMo refractory high-entropy alloy (RHEA) with ultra-fine grains was initially fabricated by mechanical alloying (MA) and subsequent spark plasma sintering (SPS). The microstructural evolution, mechanical performance and strengthening mechanisms of the alloys in various processing conditions were systematically characterized. A single body-centered cubic (BCC) solid solution phase with nanocrystalline structure was formed after milling for 30 h. Afterward, the BCC2 and Al2O3 phases were precipitated from the supersaturated BCC structure during the sintering process in the temperature range from 1100 to 1300 °C. The specimen with an average grain size of ∼0.47 µm and an precipitation phase of less than ∼0.15 µm was obtained at sintering temperature of 1200 °C, exhibiting ultra-high micro-hardness of 10.26 GPa, acceptable compressive yield strength of 1825 MPa, outstanding ultimate compressive strength of 2989 MPa and satisfactory plastic strain of 17.8% at room temperature. The excellent mechanical properties of the TiAlV0.5CrMo RHEA were dominantly attributed to the combined effects of inherent solid solution strengthening, grain boundary strengthening and precipitation strengthening. It is anticipant that the process of combining MA and SPS is the effective method to produce novel lightweight and refractory structural material with outstanding performance.

Exploration of homologous substitution element on phase ratio and high temperature properties in high Nb-containing TiAl alloy

To reveal homologous substitution and refined mechanisms, and improve mechanical properties, Ti42Al6Nb 2.5 CxTa alloys were prepared by arc melting. Element distribution, lamellar colony size, length-diameter radio of Ti2AlC phase, tensile properties, and the corresponding influence mechanism were studied. Results show that the relative contents of γ and Ti2AlC phase increase, the content of α2 phase decreases, when Ta content increases from 0 to 2.0 at%. The relative content of B2 phase increases among the lamellar colonies and the length-diameter ratio of Ti2AlC particle decreases. Lamellar colony size decreases from 24.9 to 10.6 µm. With the increase of Ta content, the supercooling at the front of the solid-liquid interface increases and the β phase is refined. The increase of the precipitated phase content leads to the increase of the number of α phase heterogeneous nucleation particles, which will refine the lamellar colony. Tensile results show that the strength increases from 238 to 513 MPa and strain increases from 2.7 % to 11.1 % of Ti42Al6Nb 2.5 C1.6Ta alloy when the tested temperature increases from 750 to 950 ℃. The high temperature tensile properties of the alloy with more Ta content are relatively higher. Ta forms large lattice distortion after solid solution into the matrix due to its large atomic size, and Ta makes more Nb dissolve into the collective to increase the effect of solid solution strengthening. Another reason is the refinement of microstructure.

Material properties of gradient copper‐nickel alloy fabricated by wire arc additive manufacturing based on bypass-current PAW

In this paper, the bypass-current plasma arc welding (BC-PAW) based on PAW was employed to fabricate copper-nickel (Cu-Ni) gradient thin-walled structures. The effect of forming accuracy and compositional homogeneity of the bypass current Cu-Ni structure was first verified by controlled experiments. The effect of Ni content on the microstructure and mechanical properties of Cu-Ni gradient structures fabricated using bypass current was then investigated, with a focus on grain orientation and texture analysis of the three intermediate Cu-Ni mixed gradient layers. The results showed that the use of bypass current in the additive manufacturing of Cu-Ni gradient structures can improve the forming accuracy and effectively eliminate lateral composition deviations within the gradient layers. In the Cu-Ni mixed gradient layers, the average grain size of the gradient layers decreased with increasing nickel content, and unusually large secondary grains appeared in different gradient layers. Due to the different Ni content, different degrees of amplitude modulation decomposition occurred in different gradient layers, resulting in changes of grain orientation and texture composition. Under the combined effects of solid solution strengthening, fine grain strengthening and amplitude modulation decomposition, the microhardness and tensile strength increased with increasing nickel content and then decreased, reaching a maximum near the side of the gradient composition biased toward nickel. The fracture analysis showed a transition from ductility to quasi-fracture.

Stability of damping capacity and mechanical properties of high-Zn-concentration Al–Zn–Mg–Sc alloy

The microstructure, damping capacity, mechanical properties, and the performance stability of high-Zn-concentration Al–Zn–Mg–Sc alloys after annealing treatment were studied. The Al–20Zn–0.5 Mg–0.5Sc alloy contained fine grains, a high number of solution atoms, Zn phases, Al 3 Sc phases, and high-density fine η and η' phases. Decreasing the Zn content led to the disappearance of the Zn phases and the decrease of intragranular η phases density and solution atom number. Increasing the Mg content did not increase the number of solution atoms but increased the size of the intragranular η phases. The Al–20Zn–0.5 Mg–0.5Sc alloy exhibited higher internal friction value and higher strength than the other two alloys because of its satisfactory grain boundaries and Al/Zn interface sliding ability at high temperature, as well as its high solid solution and second phase strengthening effects at room temperature. All annealed Al–Zn–Mg–Sc alloys exhibited excellent damping capacity and mechanical properties stability during the DMA test at the highest temperature of 360 °C due to their high structural stability. • A novel Al alloy with excellent damping capacity, mechanical properties, and performances stability was obtained. • The satisfactory GB and Al/Zn interface sliding ability led to the Al–Zn–Mg–Sc alloy exhibited well damping capacity. • The high solid solution and second phase strengthening effects led to the Al–Zn–Mg–Sc alloy exhibited high strength. • Sc addition and annealing led to the Al–Zn–Mg–Sc alloy exhibited excellent structural and properties stabilit.

Effects of phase transition on tribological properties of amorphous VAlTiCrSi high-entropy alloy film by magnetron sputtering

High-entropy alloy films have shown great potential in high-temperature antifriction and anti-wear applications . Magnetron sputtering high-entropy alloy films with uniform composition will have inevitable structural changes at high temperatures, which have an impact on their tribological behavior. In this work, amorphous VAlTiCrSi high-entropy alloy films prepared by magnetron sputtering show good thermal stability and high-temperature tribological properties. Especially at 700 °C, the structural change from an amorphous phase to a mixture consisting of body-centered cubic, Al 8 Cr 5 , (V, Ti, Cr) 5 Si 3 , and amorphous phases are responsible for the improved tribological properties. The hard body-centered cubic phase with solid-solution strengthening effect and intermetallic compounds significantly enhance the mechanical properties of VAlTiCrSi film, so as to improve the wear resistance performance of the films. The insight into the relationship between structural changes and friction properties will contribute to the design of novel high-performance high-entropy alloy films in high-temperature environments. • Amorphous VAlTiCrSi high-entropy alloy film prepared by magnetron sputtering. • Structure changes from amorphous to body-centered cubic, Al 8 Cr 5 , and (V, Ti, Cr) 5 Si 3 . • The hard phases at 700 °C improve the mechanical and tribological properties.

Solid solution strengthening of high-entropy alloys from first-principles study

• Solid solution strengthening (SSS) effects in a series of conventional alloys and high-entropy alloys are investigated. • Agreement between predicted and measured hardness is satisfactory for both alloys. • Size misfit parameters and shear modulus misfit parameters are derived from first-principles calculations. • The predicted host/alloy family-dependent fitting constants can be used to estimate the hardness of these SSS alloys. Solid solution strengthening (SSS) is one kind of strengthening mechanisms and plays an important role in alloy design, in particular for single-phase alloys including high-entropy alloys (HEAs). The classical Labusch–Nabarro model and its expansions are most widely applicable to treating SSS of solid solution alloys including both conventional alloys (CAs) and HEAs. In this study, the SSS effects in a series of Fe-based CAs and HEAs are investigated by using the classical Labusch–Nabarro model and its expansions. The size misfit and shear modulus misfit parameters are derived from first-principles calculations. Based on available experimental data in combination with empirical SSS model, we propose fitting constants ( i.e. , the ratio between experimental hardness and predicted SSS effect) for these two families of alloys. The predicted host/alloy family-dependent fitting constants can be used to estimate the hardness of these SSS alloys. General agreement between predicted and measured hardness values is satisfactory for both CAs and HEAs, implying that the proposed approach is reliable and successful.

Effect of Silicon Content on Microstructures and Properties of Directionally Solidified Fe-B Alloy.

In order to investigate the effect of Si content on the microstructures and properties of directionally solidified (DS) Fe-B alloy, a scanning electron microscope (SEM) with an energy dispersive spectrum (EDS), and X-ray diffraction have been employed to investigate the as-cast microstructures of DS Fe-B alloy. The results show that Si can strongly refine the columnar microstructures of the DS Fe-B alloy, and the columnar grain thickness of the oriented Fe2B is reduced with the increase of Si addition. In addition, Si is mainly distributed in the ferrite matrix, almost does not dissolve in boride, and seems to segregate in the center of the columnar ferrite to cause a strong solid solution strengthening and refinement effect on the matrix, thus raising the microhardness of the matrix and bulk hardness of the DS Fe-B alloy.

Nanocrystalline (AlTiVCr)N Multi-Component Nitride Thin Films with Superior Mechanical Performance.

Multi-component nitride thin films usually show high hardness and good wear resistance due to the nanoscale structure and solid-solution strengthening effect. However, the state of N atoms in the thin film and its effects on the compressive strength is still unclear. In this work, (AlTiVCr)N multi-component nitride thin films with a face-centered cubic (FCC) structure prepared by the direct current magnetron sputtering method exhibit a superior strength of ~4.5 GPa and final fracture at a strain of ~5.0%. The excellent mechanical properties are attributed to the synergistic effects of the nanocrystalline structure, covalent bonding between N and metal atoms, and interstitial strengthening. Our results could provide an intensive understanding of the relationship between microstructure and mechanical performances for multi-component nitride thin films, which may promote their applications in micro- and nano-devices.

Effect of austenitizing temperature on microstructure and properties of a high-speed cobalt steel

Abstract The effect of different austenitizing temperatures on the type, morphology, distribution of carbides and martensite content in cobalt high-speed steel is characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction and energy dispersive spectrometry. The results show that the eutectic MC carbides hardly dissolve during austenitizing process, and the lamellar M2C carbides decompose into MC and M6C carbides at 1100 °C. A large amount of M23C6 carbides uniformly distributed on the matrix are dissolved into austenite at 1100 °C. With the increase of austenitizing temperature, alloy element dissolves into matrix and the effect of solid solution strengthening of martensite enhances, which increases the hardness of cobalt high-speed steel. However, when the austenitizing temperature exceeds 1050 °C, the excess alloying elements in the matrix reduce the Ms point and increase the volume fraction of retained austenite, resulting in decrease of hardness of cobalt high-speed steel. The peak hardness with 66.4 HRC appears when the austenitizing temperature reaches 1050 °C.

Fracture behaviors of Ti(C, N)-based cermets with different contents of metal binder

Ti(C0.7,N0.3)-Mo2C–Ni cermets are fabricated by powder metallurgy methods. We systematically investigate the microstructure, fracture morphology, crack propagation mechanism, and interface characteristics of Ti(C, N)-based cermets with different Ni binder contents.The increased dissolution of carbides and carbonitrides leads to a large amount of (Mo,Ti)(C,N) solid solution precipitates, which then spontaneously nucleate, resulting in a significant increase in the content of white core-gray rim grains in the cermets with a high binder content. The increased Ni binder largely improves the flexural strength and fracture toughness of the Ti(C,N)-based cermets because of the ductile dispersion toughening. The rim-core interfaces have a superior atomic coherent relationship in all Ti(C,N)-based cermets owing to the small lattice mismatch. The lattice mismatch of the interface between the rim phase and metal binder is remarkably decreased with the increase in the binder content to construct an atomic coherent relationship. Thus, the increased Ni binder promotes atomic ordering at the interface between the ceramic grains and binder and strengthens the grain boundary. The characteristic (111) peak of nickel shifts to a larger angle due to the reduction in the Ni-based solid solution lattice distortion. Therefore, the effect of solid solution strengthening is diminished with the increase in binder content, which results in a decreased binder strength. In the Ti(C,N)-based cermets with low metal binder contents, the fracture of the grain boundary between the ceramic grains and binder is the predominant failure mechanism. The intergranular crack accompanied by crack branching is the main characteristic of crack propagation. A hybrid fracture mode of intergranular and transgranular cracks is observed in the Ti(C,N)-based cermets with a moderate binder content. As the binder content further increases, the plastic yield deformation and subsequent tearing of the metal binder are the main fracture characteristics because of grain boundary strengthening and decreased strength of the binder.

Structure, composition and mechanical properties of reactively sputtered (TiVCrTaW)Nx high-entropy films

Nitride and metallic films multi-element (TiVCrTaW)Nx high-entropy alloy were deposited on silicon wafers by pulse DC magnetron sputtering. The microstructure and mechanical properties of the films prepared with different nitrogen gas flow ratios were studied. The results show that the concentration of nitrogen approached the stoichiometric composition at nitrogen gas ratio RN ≥ 33.3 %. The alloy film deposited with pure argon atmosphere exhibited a BCC structure and a very smooth surface, while an FCC with (111) or (200) preferred orientation and granular surface morphologies was observed in those films prepared with introduction of nitrogen gas. The (TiVCrTaW)Nx films exhibited enhanced hardness upon the addition of nitrogen probably due to the solid-solution strengthening effect and grain refinement. The nitride film achieved the highest hardness and Young’s modulus of 38 GPa and 340 GPa, respectively. The results show that the deposition atmosphere plays a vital rule in the structure and the properties of the (TiVCrTaW)Nx high-entropy films.

Laser-clad Al-Ti-Zr and Cr-Ti-Zr coatings on Zr alloy: composition-induced microstructural and hardness differences

In this study, Al-Ti-Zr and Cr-Ti-Zr metallic coatings with thichness of 250-280 μm were fabricated successfully on Zr alloy using pulsed laser cladding. By jointly employing multiple characterization techniques, microstructural characteristics of the coatings were probed with their formation reasons explored. The Al-Ti-Zr coating consists of a single BCC solid-solution phase (average size 8.6 ± 6.3 μm) with hardness of 405.5 ± 16.6 HV that is more than twice that of the substrate (198.7 ± 2.0 HV). Such marked hardening is mainly related to the contribution from the solid-solution strengthening produced by Al and Ti. The Cr-Ti-Zr coating consists of cellular BCC phase (average size 0.9 ± 0.4 μm) and C14-type Cr2(Ti,Zr) Laves phase with nanoscale lamellar structures. Its average hardness is 584.8 ± 33.6 HV, about three times of that of the substrate, which can be ascribed to synergistic effects of solid-solution, grain refinement and second phase strengthening. The formation of the single BCC solid-solution phase in the Al-Ti-Zr coating is mainly due to the relatively small differences in atomic size and electronegativity between Al, Ti and Zr. For the Cr-Ti-Zr coating, however, due to large atomic size and electronegativity differences between Cr and Zr (as well as Cr and Ti), Cr2(Ti,Zr) Laves phase was formed in addition to the BCC phase.

Effect of Bi, Sb, and Ti on Microstructure and Mechanical Properties of SAC105 Alloys.

The Sn-Ag-Cu (SAC) solder alloys with a low Ag (Ag < 3 wt.%) content have attracted great attention owing to their low cost, increased ability in bulk compliance, and plastic energy dissipation. However, some of their mechanical properties are generally lower than the SAC alloys with a higher Ag content. Adding alloying elements is an effective approach for improving the mechanical properties of the SAC alloys. In this study, the effect of Bi, Sb, and Ti on Sn-1 wt.%Ag-0.5 wt.%Cu (SAC105) solder alloys was investigated. The SAC solders with four compositions: SAC105-1 wt.%Bi, SAC105-1 wt.%Sb, SAC105-1 wt.%Bi-1 wt.%Sb, SAC105-1 wt.%Bi-1 wt.%Sb-0.4 wt.%Ti were prepared. The microstructure and phase compositions were characterized using electron scanning microscopy, and X-ray diffraction. The thermal properties and wettability were also examined. Uniaxial tensile tests and nano-indentation tests were conducted to evaluate the mechanical properties. The results show that adding Bi or Sb could increase the strength of SAC105 alloys mainly due to the solid solution strengthening effect. The creep resistance of SAC105 alloys was also improved with the additions of Bi and Sb. The co-additions of Bi and Sb into SAC105 alloys exhibit an enhanced creep resistance than that calculated by the theoretical calculation. The further addition of Ti into SAC105-1Bi-1Sb alloys demonstrated a much-improved creep resistance, which could be attributed to the synergistic effects of both solid solution strengthening and the precipitation hardening effects.

Research on formability, microstructure and mechanical properties of selective laser melted Mg-Y-Sm-Zn-Zr magnesium alloy

Selective laser melting (SLM) refers to a laser additive manufacturing technology. It shows its advantages of high efficiency and is capable of processing arbitrary complex structural parts. However, the SLM of magnesium alloy is highly challenging and should be studied in depth due to the low melting and boiling point of magnesium alloy. In this study, selective laser melting (SLM) technology was used to manufacture the Mg-Y-Sm-Zn-Zr alloy. Microstructure characteristics and performance mechanism of the SLMed samples were investigated. As revealed by the results, samples characterized by relatively high densities and low surface roughness could be produced when the energy density was 83.3–166.7 J/mm 3 . The highest density of 97.8% could be obtained when the energy density was 125.7 J/mm 3 . The molten pool was found to consist of slender columnar grains at the edge and a small amount of equiaxed grains at the top, while the grains below the molten pool were coarsened under the action of the thermal influence. The role played by Y 2 O 3 in the solidification of SLM was characterized using the degree of lattice mismatch. Impacted by the high lattice mismatch between Y 2 O 3 and Mg, Y 2 O 3 could not serve as an effective heterogeneous nucleation particle. The highest comperssive performance was obtained at energy density of 125.7 J/mm 3 (YS = 304 ± 5 Mpa, UTS = 394 ± 5 Mpa). The main strengthening mechanism was fine-grain strengthening, followed by precipitation strengthening and the effect of solid solution strengthening was not obvious. This work provides a certain guiding significance for the follow-up research of SLMed rare earth magnesium alloy. • SLM process parameters of Mg-Y-Sm-Zn-Zr which can obtain ideal relative density and surface roughness were determined. • The influence of Y and Zr elements on the solidification behavior of SLMed Mg-Y-Sm-Zn-Zr was determined. • The orientation relationship between precipitated particles and the magnesium matrix was studied. • The improvement of the compressive properties of the SLMed sample was analyzed.

Effect of bonding temperature and heat treatment on microstructure and mechanical property of Mg−6Gd−3Y alloy vacuum diffusion bonded joints

Diffusion bonding of as-cast Mg−6Gd−3Y magnesium alloy was carried out at temperatures of 400−480 °C with bonding pressure of 6 MPa for 90 min. Diffusion bonded joints were solution treated at 495 °C for 14 h and then aged at 200 °C for 30 h. Microstructures and mechanical properties of joints were analyzed. The results showed that rare earth elements and their compounds gathering at bonding interface hindered the grain boundary migration crossing bonding interface. Tensile strength of as-bonded and as-solution treated joints increased firstly and then decreased with the bonding temperature increasing due to the combined effects of grain coarsening and solid-solution strengthening. As-bonded and solution-treated joints fractured at matrix except the joint bonded at 400 °C, while aged joints fractured at bonding interface. The highest ultimate tensile strength of 279 MPa with elongation of 2.8% was found in joint bonded at 440 °C with solution treatment followed by aging treatment.