Influence of Pd addition on the creep behavior of AZ61 magnesium alloy

The effect of Pd addition (0, 2, and 4 wt%) on the microstructure and creep properties of permanent mold AZ61 (Mg-6Al-1Zn) alloy has been studied. The results indicate that Pd addition introduces a lamella-shaped Al₄Pd phase at the grain boundary, in addition to the Mg₁₇Al₁₂ (β) phase. The addition of Pd also suppresses the precipitation of the Mg₁₇Al₁₂ phase and residual Al at grain boundaries during solidification. These effects lead to an improvement in the creep behavior of AZ61. Moreover, extended steady-state creep and reductions in both the minimum creep rate and total creep strain are also observed in the case of 4 wt% Pd addition.     

Microstructure and mechanical properties of as aged Mg–3Sn–1Al and Mg–3Sn–2Zn–1Al alloy

Effect of Zn on the microstructure, age hardening response and mechanical properties of Mg–3Sn–1Al alloy which is immediately aged at 180°C after extrusion process (T5) was investigated. It was found that the Zn can refine the microstructure, remarkably improve the aging response with the peak hardness increases to 75 HV and the time to peak hardness reduces from ～110 to ～60 h, which is attributed to the solid solution hardening of Al, Zn and an amount of finer Mg₂Sn precipitates. The as aged Mg–3Sn–2Zn–1Al alloy exhibits better mechanical property at room temperature or 150°C than that of Mg–3Sn–1Al alloy, which is ascribed to the fine grained microstructure and thermally stable Mg₂Sn particles dispersed at grain boundaries and in the matrix.     

Microstructure and mechanical properties of as-extruded AZ80–xSn magnesium alloys

The effect of 0–2?wt-% Sn addition on AZ80 magnesium alloys after 350°C extrusion has been studied by analysing microstructure and mechanical properties. The results indicated that dynamically recrystallised grains were fine and homogeneous with less than 1?wt-% Sn addition. In AZ80–0.5Sn alloy, a large number of Mg₁₇Al₁₂ precipitated phases formed in grains and at grain boundaries during extrusion process. With more than 1?wt-% Sn addition, the size of dynamically recrystallised grains increased and the number of Mg₁₇Al₁₂ phases decreased. The strength of as-extruded AZ80–0.5Sn alloy enhanced largely as compared with that of the as-extruded AZ80 alloy. AZ80–0.5Sn alloy had the outstanding tensile and compressive properties.     

Influence of Grain Size and Texture on the Yield Asymmetry of Mg-3Al-1Zn Alloy

The yield asymmetry between compression and tension of magnesium alloy Mg-3Al-1Zn(AZ31) with different grain sizes and textures has been studied by tensile and compressive testing of as-cast,as-extruded and equal channel angular pressed(ECAPed) specimens.The significant yield asymmetry(the ratio of yield strength between compression and tension σyc/σyt is ～0.44) was found in as-extruded specimens and the corresponding microstructure evolution during deformation revealed that {10 ˉ 12} tensile twinning is the underlying reason for the large yield asymmetry.Strong texture and grain size are influential factors for large yield asymmetry.The separate contributions of grain size and texture on yield asymmetry were investigated.     

Influence of undissolved second-phase particles on dynamic recrystallization behavior of Mg-7Sn-1Al-1Zn alloy during low-and high-temperature extrusions

This study investigates the effects of fine and coarse undissolved particles in a billet of the Mg-7Sn-1Al-1Zn (TAZ711) alloy on the dynamic recrystallization (DRX) behavior during hot extrusion at low and high temperatures and the resultant microstructure and mechanical properties of the alloy.To this end,partially homogenized (PH) and fully homogenized (FH) billets are extruded at temperatures of 250 and 450 ℃.The PH billet contains fine and coarse undissolved Mg2Sn particles in the interdendritic region and along the grain boundaries,respectively.The fine particles (＜1 μm in size) retard DRX during extrusion at 250 ℃ via the Zener pinning effect,and this retardation causes a decrease in the area fraction of dynamically recrystallized (DRXed) grains of the extruded alloy.In addition,the inhomogeneous distribution of fine particles in the PH billet leads to the formation of a bimodal DRXed grain structure with excessively grown grains in particle-scarce regions.In contrast,in the FH billet,numerous nanosized Mg2Sn precipitates are formed throughout the material during extrusion at 250 ℃,which,in turn,leads to the formation of small,uniform DRXed grains by the grain-boundary pinning effect of the precipitates.When the PH billet is extruded at the high temperature of 450 ℃,the retardation effect of the fine particles on DRX is weakened by their dissolution in the α-Mg matrix and the increased extent of thermally activated grain-boundary migration.In contrast,the coarse Mg2Sn particles in the billet promote DRX during extrusion through the particle-stimulated nucleation phenomenon,which results in an increase in the area fraction of DRXed grains.At both low and high extrusion temperatures,the extruded material fabricated using the PH billet,which contains both fine and coarse undissolved particles,has a lower tensile strength than that fabricated using the FH billet,which is virtually devoid of second-phase particles.This lower strength of the former is attributed mainly to the larger grains and/or absence of nanosized M2Sn precipitates in it.     

Effect of La<Subscript>2</Subscript>O<Subscript>3</Subscript> addition on the microstructure of partially remelted Mg-9Al-1Zn alloy

The effect of La₂O₃ addition on the microstructure of partially remelted Mg-9Al-1Zn (AZ91D) alloy was studied. The results indicate that small amounts of La₂O₃ additions to AZ91D alloy refined the partially remelted microstructure and caused the formation of new phase- LaAl₄ in the microstructure. Moreover, the grain size of the partially remelted alloys is decreased with the increasing of La₂O₃ addition. In as-cast microstructure the LaAl₄ phases have two morphologies: needle-like and particle-shape. The presence of more LaAl₄ phases, especially, the particle-shape LaAl₄ which dispersedly distributed within the grains can induce more dislocations, which can result in the occurring of a large amount of recrystallizations. Moreover, these LaAl₄ phases can also restrain the growth and combination of the recrystallizations and partially remelted initial grains during the subsequent heat-treatment.     

The microstructure and mechanical properties of low-temperature and low-speed extruded Mg–3Sn–2Al–1Zn alloy

ABSTRACT

The microstructure and mechanical properties of the Mg–3Sn–2Al–1Zn (TAZ321) alloy extruded at 180–250°C and at a ram speed of 0.08?mm/s were investigated by optical microscope, X-ray diffraction, scanning electron microscope, transmission electron microscope, tensile testing and microhardness tester. The results indicate that the as-extruded alloy shows ultrafine dynamic recrystallisation grains, nanoscale Mg₂Sn precipitates of 50–80?nm, strong texture and excellent mechanical properties, the degree of which mainly depends on the extrusion temperature. The tensile yield strength and elongation vary from 413?MPa and 6.7% of TAZ321 extruded at 180°C to 312?MPa and 14.1% of TAZ321 extruded at 250°C, which can be regulated flexibly.     

Effect of addition of Ce in Sn–30Zn solder on the structure and properties of the Mg/Al-brazed joint

AZ31B Mg alloy and 6061 Al alloy are joined using low-temperature soldering with Sn–30Zn–xCe solder alloy. The effect of Ce content in Sn–30Zn–xCe solders on microstructure evolution and mechanical properties of the different brazed joints are investigated. The experimental results show that adding appropriate amount of Ce into Sn–30Zn solder is conducive to decreasing the amount of Mg₂Sn intermetallic compounds and increasing the amount of Al–Sn–Zn solid solutions in the soldering zone of the brazed joint, which restricts the drawback of the formation of hard and brittle Mg₂Sn intermetallic compounds and enhances the mechanical property of soldered joint. The average shear strength of the Mg/Sn–30Zn–0.05Ce/Al-brazed joint can reach 77.48 MPa. Results also indicate that the excessive content of Ce leads to the formation of some Ce–Zn and Ce–Sn intermetallic compounds in soldering zone and subsequently decreases the strength of soldered joint.     

Effect of Sn on the Microstructure and Mechanical Properties of Mg-5Al-2Si Alloys

The effect of Sn addition on the microstructures and mechanical properties of Mg-5Al-2Si alloys was investigated with variations of Sn contents （3 and 6 wt pct）. The microstructure of the alloy was characterized by the presence of Mg2Sn particles within matrix and at grain boundaries. As the Sn contents increased, yield and ultimate tensile strength were increased at room temperatures and 150℃. Creep properties were improved with the increasing amount of Sn due to the fine precipitation of Mg2Sn phases within grain during creep.     

Development of ternary Mg based alloy for soldering of AZ31B magnesium alloy

Abstract

Two kinds of ternary Mg based alloys were designed to join the AZ31B magnesium alloy plates by high frequency induction soldering with argon shielding gas. The microstructures and properties of the filler metals and joints were investigated by SEM, X-ray diffraction, differential scanning calorimetry, spreading test and tensile test. The results have shown that the microstructures of Mg–31·5Al–10Sn filler metal mainly consist of Mg₁₇Al₁₂, Mg₂Sn and a trace amount of α-Mg phases, while the microstructures of Mg–29·5Zn–1Sn filler metal include α-Mg phase and Mg₇Zn₃ with a trace of α-Mg and Mg₂Sn phases. Both of the filler metals have narrow melting zones; however, the spreading area of the Mg–31·5Al–10Sn filler metal is much larger than that of the Mg–29·5Zn–1Sn filler metal on the AZ31B base metal. The average tensile strength of solder joints with Mg–31·5Al–10Sn filler metal is a little higher than that of the latter solder joints with Mg–29·5Zn–1Sn filler metal.     

Effect of Pd on microstructures and tensile properties of as-cast Mg-6Al-1Zn alloys

The effects of Pd on the microstructure and mechanical properties of Mg-6Al-1Zn alloys were investigated. Mg-6Al-1Zn-xPd (x = 0-6 wt.%) alloys were prepared using a permanent mould casting method. The microstructure of the as-cast alloys was characterized by the presence of Mg₁₇Al₁₂ and Al₄Pd phases. The volume fraction of the Al₄Pd phase was increased by the addition of 1-6 wt.%Pd but the volume fraction of the Mg₁₇Al₁₂ phases decreased. At room temperature, the tensile strength increased with increasing Pd addition up to 2 wt.%Pd, and the elongation to fracture decreased with a concomitant increase in the aggregation of the coarse Al₄Pd phase. At 150 °C, the tensile strength increased with the addition of Pd. Therefore, the room and elevated temperature tensile properties of as-cast Mg-6Al-1Zn alloys can be improved by Pd addition.     

Microstructure and tensile properties of as extruded and as aged Mg–Al–Zn–Mn–Sn alloy

The effect of 0–4 wt-% Sn addition on the microstructure and tensile properties of AZ80 alloys was investigated. The results indicated that Mg₂Sn particles were barely formed during the extrusion process until the content of Sn is >2 wt-%. The dislocation density in alloys after extrusion declined with the addition of Sn due to the promotion of dynamic recrystallisation after adding Sn. In aging treatment, Mg₁₇Al₁₂ precipitates were promoted by Sn and the phases distributed uniformly at low density level of dislocation. The AZ80-2 wt-% Sn alloy possessed the excellent tensile properties in as extruded and as aged state.     

Mechanical characterization and corrosion behavior of newly designed Sn and Y added AZ91 alloy

This paper deals the effect of Sn and Y additions on the microstructure, mechanical and corrosion properties of AZ91 alloy. It is found that by the addition of Sn, the formation and growth of discontinuous precipitate get suppressed and new intermetallic Mg₂Sn phase is formed. In the case of Y addition together with Sn, the grain size gets refined, the volume of Mg₁₇Al₁₂ gets decreased and new intermetallic Al₂Y phase is observed. Improved room and high temperature tensile properties are obtained in as-cast and aged Sn and Y added AZ91 alloy. However, maximum properties are obtained for the alloy having combined addition of 0.5 wt.% Sn and 0.9 wt.% Y. Improved corrosion resistance is also noticed with the addition of Sn and Y elements.     

Microstructural characteristics of lap joint between magnesium alloy and mild steel with and without the addition of Sn element

Lap joint of AZ31B Mg alloy to Q235 steel by hybrid laser-TIG welding was studied. Microstructures of Sn-free and Sn-added joint were investigated, and the intermediate phase of Sn-added joints was also inspected. In contrast with the Sn-free joints, intermetallic compound Mg₂Sn with dendritic structure distributed in the grain boundaries of Mg alloy was identified; Gaps at the interfaces were vanished as the wettability of Mg alloy with the addition of Sn on steel was improved. Big particles in fusion zone became even smaller or disappeared in the Sn-added joints.     

Deformation mechanism and dynamic precipitation in a Mg-7Al-2Sn alloy processed by surface mechanical attrition treatment

The effect of second phases on the deformation mechanism of as-cast, solution-treated and aged Mg-7Al-2Sn (AT72) alloys during surface mechanical attrition treatment (SMAT) was investigated. Twinning was suppressed in the alloys containing second phases, which can provide nonuniform microstructures and phase boundaries as dislocation sources. Dynamic precipitation in AT72 alloys was studied during SMAT deformation as well. Mg₂Sn particles can dynamically precipitate on the surface of all AT72 alloys during SMAT process. The quantity of Mg₂Sn particles in the as-cast alloy, which is determined by the initial quantity of second phases, is larger than that of T4 and T6 alloys after the SMAT process.     

Superplastic behavior and microstructural stability of friction stir processed AZ91C alloy

Superplastic behavior of a solution treated and friction stir processed (FSP) AZ91C alloy is studied. These studies are conducted in the temperature range of 300–375 °C and strain rates (SRs) in the range of 1 × 10^?4–3 × 10^?3 s^?1. Microstructural stability of the FSP alloy is also studied in comparison to the AZ31, AZ61, and AZ91 alloys processed by various routes. High SR sensitivity in the range of 0.33–0.39 and grain size stability till 350 °C is observed for the FSP alloy. The FSP AZ91C alloy showed better thermal stability in comparison to AZ31 and AZ61 alloys. Kinetics of superplastic deformation of the FSP alloy is found to be slower as compared to AZ31 and AZ61 alloys processed by various routes, which is due to the presence of significant amount of second phase precipitates, such as, β-Mg₁₇(Al,Zn)₁₂, Mg₂Si, and Al₈Mn₅ in the FSP alloy. However, these precipitates contributed for better thermal stability of the microstructure of FSP AZ91C alloy.     

Microstructural evolution and superplasticity of rolled Mg-9Al-1Zn

Microstructural evolution and superplasticity of a Mg-9Al-1Zn alloy rolled at 673 K were investigated at 573 K and 1.5×10⁻³ s⁻¹. The grain size of the as-rolled Mg alloy was 39.5 μm. However, the grain size of the specimen deformed to a true strain of 0.6 was 9.1 μm. The grain refinement was attributed to dynamically continuous recrystallization during an initial stage of tensile test. Stabilization of subgrain boundaries by fine particles and stimulation of continuous recrystallization by prior warm-deformation were not needed to attain dynamically continuous recrystallization in the Mg alloy. As a result of the grain refinement, the rolled Mg alloy exhibited superplastic behavior.     

Effect of the Zn content on the microstructure and mechanical properties of indirect-extruded Mg–5Sn–xZn alloys

Mg–5Sn–xZn alloys with varying Zn contents were subjected to indirect extrusion and the effects of the Zn content on the microstructure and mechanical properties of the as-extruded alloys were investigated. It was found that, the grain size and the basal texture are basically similar, however, the amount of fine particles consisting of Mg₂Sn and MgZn phases increases markedly as the Zn content increases. A higher number of these particles would be responsible for the better comprehensive mechanical properties as well as a lower degree of yield asymmetry.     

Improved plasticity of Mg-Al-Zn alloy by electropulsing tension

The effect of electropulsing tension (ET) on the elongation to failure and microstructure of Mg-3Al-1Zn (AZ31) alloy was studied. It was found that electropulsing increased the elongation to failure dramatically at a high strain rate of 2.5 × 10^− 2 s^− 1, compared with the non-ET sample. The mechanism for increasing the elongation was proposed mainly based on dynamic recrystallization (DRX). The results in this investigation indicated that an ideal improvement in plasticity and fine equiaxial grains were obtained at a low temperature and a high strain rate due to the coupling of the thermal and athermal effects of ET. It is different from conventional theories.     

Effect of Al on the microstructure and mechanical properties of Mg–6Zn–2Sn–0.5Mn alloy

The microstructure and mechanical properties of Mg–6Zn–2Sn–0.5Mn–xAl (x?=?0, 1, 2, 3) alloy are investigated. The addition of Al leads to the refinement of grain size and the formation of Al₆Mn, Mg₃₂(Al,Zn)₄₉ also forms when the amount of Al is higher than 2?wt-%. Because of the addition of Al, the precipitates in the alloy after ageing treatment are refined. The alloy containing 1?wt-% Al shows good mechanical properties in the as-cast state which is attributed to the refined grains and low volume fraction of large second phases, it also shows high strength after ageing treatment resulted mainly from the homogeneously distributed fine precipitates, the yield strength, ultimate tensile strength and elongation are 183, 310?MPa and 11%, respectively.