Effects of Cu content on microstructure and mechanical properties of Al–14.5Si–0.5Mg alloy

This study elucidates how Cu content affects the microstructure and mechanical properties of Al–14.5Si–0.5Mg alloy, by adding 4.65 wt.% and 0.52 wt.% Cu. Different Fe-bearing phases were found in the two alloys. The acicular β-Al₅FeSi was found only in the high-Cu alloy. In the low-Cu alloy, Al₈Mg₃FeSi₆ was the Fe-bearing phase. Tensile testing indicated that the low-Cu alloy containing Al₈Mg₃FeSi₆ had higher UTS and elongation than the high-Cu alloy containing the acicular β-Al₅FeSi. It is believed that the presence of the acicular β-Al₅FeSi in the high-Cu alloy increased the number of crack initiators and brittleness of the alloy. Increasing Cu content in the Al–14.5Si–0.5Mg alloy also promoted solution hardening and precipitation hardening under as-quenched and aging conditions, respectively. The hardness of the high-Cu alloy therefore exceeded that of low-Cu alloy.     

Effects of trace Er addition on the microstructure and mechanical properties of Mg–Zn–Zr alloy

The effects of trace Er addition on the microstructure in Mg–9Zn–0.6Zr alloy during casting, homogenization, pre-heating, and hot extrusion processes were examined. The mechanical properties of alloys with and without Er were compared. The results showed that Er exhibited a lower solubility in solid magnesium and formed thermally stable Er- and Zn-bearing compounds. The Er-bearing alloy exhibited a considerably improved deformability, as well as a fine and uniform microstructure. Moreover, dynamic precipitation of fine MgZn₂ particles with a modified spherical morphology occurred during hot extrusion, resulting in a tensile yield strength of 313 MPa and a high elongation to failure value of 22%. Further aging of the Er-bearing alloy led to an increment of another 30 MPa in yield strength. In addition, Er markedly increased the thermal stability of the alloy structure.     

Effects of samarium on microstructure and mechanical properties of Mg–Y–Sm–Zr alloys during thermo-mechanical treatments

Microstructure and mechanical properties of Mg–4Y–xSm–0.5Zr (x = 1, 4, 8) alloys during thermo-mechanical treatments were investigated in this study. Mg–4Y–4Sm–0.5Zr alloy exhibits higher tensile strength but lower elongation than Mg–4Y–1Sm–0.5Zr alloy during the thermo-mechanical treatments. Large amount of intermetallic phases still remained at grain boundaries in Mg–4Y–8Sm–0.5Zr alloy after solution. These undissolved phases can strengthen the grain boundaries at temperatures higher than 573 K. But the room temperature mechanical properties of Mg–4Y–8Sm–0.5Zr alloy during the thermo-mechanical treatments were greatly weakened for the brittleness of these undissolved intermetallic phases.     

Effects of Zn content on microstructures and mechanical properties of as cast Mg–Zn–Y–Zr alloys

Abstract

In the present work, the effects of Zn content on the microstructures and mechanical properties of as cast Mg–xZn–5Y–0·6Zr alloys (x?=?2, 5, 8 and 13 wt-%) have been investigated. The results show that the ternary Mg–Zn–Y phase compositions change with Zn/Y ratios induced by the change in Zn content. It is found that the fracture is mainly decided by the characteristics and distribution of second phase rather than the grain size. The influences of these phases, especially the W phase, on the mechanical properties of the alloys have been discussed. Both ultimate tensile strength (UTS) and elongation decrease with the increase in Zn content, while the instance of yield strength (YS) is just the reverse. The W phase is easily cracked because of its brittleness and easy to result in decohesion from the matrix because of the weak atomic bonding, which greatly degrade the UTS and elongation. It can be concluded that the YS closely depends on the grain size, while UTS and elongation closely depend on the volume fraction of eutectic compound (α-Mg+W phase).     

Effects of processing parameters on microstructure and mechanical properties of squeeze-cast Mg–12Zn–4Al–0.5Ca alloy

In this paper, a new magnesium alloy Mg–12Zn–4Al–0.5Ca (ZAX12405) was prepared by squeeze casting. The effects of processing parameters including applied pressure, pouring temperature and dwell time on the microstructure and mechanical properties of squeeze-cast ZAX12405 alloy were investigated. It was found that squeeze-cast ZAX12405 alloy exhibited finer microstructure and much better mechanical properties than gravity casting alloy. Increasing the applied pressure led to significant cast densification and a certain extent of grain refinement in the microstructure, along with obvious promotion in mechanical properties. Lowering the pouring temperature refined the microstructure of ZAX12405 alloy, but deteriorated the cast densification, resulting in that the mechanical properties firstly increased and then decreased. Increasing the dwell time promoted cast densification and mechanical properties just before the solidification process ended. A combination of highest applied pressure (120 MPa), medium pouring temperature (650 °C) and dwell time (30 s) brought the highest mechanical properties, under which the ultimate tensile strength (UTS), yield strength (YS) and elongation to failure (E_f) of the alloy reached 211 MPa, 113 MPa and 5.2% at room temperature. Comparing with the gravity casting ZAX12405 alloy, the UTS and E_f increased 40% and 300%, respectively. For squeeze-cast Mg–12Zn–4Al–0.5Ca alloy, cast densification was considered more important than microstructure refinement for the promotion of mechanical properties.     

Effects of Sn on microstructure and mechanical properties of as-rolled Mg–5Zn–1Mn alloy

Effects of Sn on microstructure and mechanical properties of Mg–5Zn–1Mn alloy subjected to high strain rate rolling (9.1?s^-1), 300°C and 80% pass reduction are investigated. With higher Sn content, the dynamic recrystallisation (DRX) grain size gradually decreases due to the stronger pinning of nano-scale precipitates at grain boundaries and the DRX fraction first increases due to the enhanced effect on DRX by decreasing stacking fault energy and then decreases due to more precipitates at grain boundaries. Ultimate tensile strength (UTS) and elongation to rupture (Er) of as-rolled alloys increase and then decrease. Alloy with 0.9 mass% Sn exhibits the highest DRX fraction (95?vol.-%), the finer DRX grain size (1.22?µm), UTS of 358?MPa and Er of 20.4%.     

Effects of Zn on microstructure,mechanical properties and corrosion behavior of Mg–Zn alloys

In this study, binary Mg–Zn alloys were fabricated with high-purity raw materials and by a clean melting process. The effects of Zn on the microstructure, mechanical property and corrosion behavior of the as-cast Mg–Zn alloys were studied using direct observations, tensile testing, immersion tests and electrochemical evaluations. Results indicate that the microstructure of Mg–Zn alloys typically consists of primary α-Mg matrix and MgZn intermetallic phase mainly distributed along grain boundary. The improvement in mechanical performances for Mg–Zn alloys with Zn content until 5% of weight is corresponding to fine grain strengthening, solid solution strengthening and second phase strengthening. Polarization test has shown the beneficial effect of Zn element on the formation of a protective film on the surface of alloys. Mg–5Zn alloy exhibits the best anti-corrosion property. However, further increase of Zn content until 7% of weight deteriorates the corrosion rate which is driven by galvanic couple effect.     

Influence of oxygen content on microstructure and mechanical properties of Ti–Nb–Ta–Zr alloy

The influence of oxygen content on microstructure and mechanical properties of Ti–22.5Nb–0.7Ta–2Zr (at.%) alloy was investigated in this work. According to experiments, the grains were refined apparently when the oxygen content was between 1.5% and 2.0%. The ultimate tensile strength (UTS) increased and elongation decreased with increasing oxygen content. But at the content of 1.0%, the elongation was nearly the same to that of the original alloy (about 16%). The elastic modulus remained comparatively low (<65 GPa) when the content was lower than 1.5%, and then increased dramatically. Therefore, there existed the best oxygen content-1.0%, at which fine grains were obtained, as well as UTS of 750 MPa, elongation of 16% and elastic modulus of 65 GPa. The Ti–22.5Nb–0.7Ta–2Zr–1.0O alloy maintained typical ductile fracture characteristics of beta titanium alloy, and had a little superelasticity.     

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.     

The influences of rare earth content on the microstructure and mechanical properties of Mg–7Zn–5Al alloy

The influences of rare earth (RE) on the microstructure and mechanical properties of Mg–7Zn–5Al alloy were studied. The results indicate that both the dendrite and grain size of the alloy can be refined by low RE addition. The Al₂REZn₂ phase will be formed with increasing the RE content, however the high RE addition results in the grain coarsening in the alloy due to the decrease of the contribution of Al and Zn solutes on the grain refinement. The strengthening and weakening mechanisms caused by RE addition only lead to the obviously improve on the room temperature ultimate tensile strength. The mechanical properties of the studied alloys can be improved by aging treatment, and the aged Mg–7Zn–5Al–2RE alloy exhibits optimal mechanical properties at room temperature.     

Effects of ECAE temperature and billet orientation on the microstructure,texture evolution and mechanical properties of a Mg–Zn–Y–Zr alloy

Single-pass equal channel angular extrusion (ECAE) experiments of an extruded Mg–Zn–Y–Zr alloy with an intense initial basal texture were performed in two inter-perpendicular billet orientations and at 473 and 623 K. The study was aimed to determine the effects of ECAE temperature and billet orientation on the microstructure, texture evolution and mechanical properties of the ECAEed alloy. It was found that the grain refinement achieved through the single-pass ECAE in the Orient-I billet orientation (the normal direction (ND) of the extruded plate parallel with the ECAE exit direction) was more effective than that in the Orient-II billet orientation (the ND of the extruded plate perpendicular to the ECAE exit direction). The average grain sizes after ECAE at 473 K were much smaller than those after ECAE at 623 K. The pole figures of the alloy ECAEed at 473 K showed that most of the basal planes in the Orient-I and Orient-II samples were inclined about 40° and 35°, respectively, with respect to the longitudinal direction of the ECAE extrudate. However, for the alloy ECAEed at 623 K, most of the basal planes were parallel with the longitudinal direction of the ECAE extrudate. It was remarkable that the yield strengths of the alloy ECAEed at 473 K were lower than those at 623 K. The peculiar relationship between ECAE temperature and the mechanical properties of the alloy was ascribed to the texture evolution during ECAE.     

Effects of Si addition on microstructure and mechanical properties of Mg–8Gd–4Y–Nd–Zr alloy

Effects of Si addition (1.0 wt.%) on microstructure and mechanical properties of Mg–8Gd–4Y–Nd–Zr alloy have been investigated using scanning electron microscopy (SEM) equipped with energy dispersive spectrum (EDS), X-ray diffraction (XRD), hardness measurements and tensile testing. The results indicated that the addition of Si led to the formation of Mg₂Si and (RE + Si)-rich particles, which enhanced the Young’s modulus of the alloy by 7 GPa while decreased the yield strength and ultimate strength by 10 MPa and 31 MPa, respectively. The tensile properties of the Mg–8Gd–4Y–Nd–Zr–Si alloy are as follows: Young’s modulus E = 51 GPa, yield strength σ_0.2 = 347 MPa, ultimate strength σ_b = 392 MPa and elongation δ = 2.7%. The increase in Young’s modulus was attributed to the formation of particles with high Young’s modulus, while the decrease in strength was ascribed to the decrease in volume fraction of metastable β′ precipitates caused by the consumption of rare earth atoms due to the formation of the rare earth containing particles.     

Influence of Sc and Zr additions on microstructure and properties evolution of Al–Zn–Mg alloy

Journal of Materials Science - In this study, the effects of different Sc?+?Zr compound addition on the tensile properties, impact toughness, stress corrosion cracking (SCC) properties,...     

Effect of cooling aging on microstructure and mechanical properties of an Al–Zn–Mg–Cu alloy

In the present work, Al–Zn–Mg–Cu alloy was aged by non-isothermal cooling aging treatment (CAT). At high initial aging temperature (IAT), the hardness was decreased with the decreased cooling rate. However, when IAT was lower than 180 °C, the hardness was increased with the decreased cooling rate. Conductivity was increased with the decreased cooling rate regardless of IAT. The tensile strength, yield strength and conductivity of Al alloy after (200–100 °C, 80 °C/h) CAT were increased 2.9%, 8.1% and 8.3% than that after T6 treatment, respectively. With an increase of IAT and decrease of cooling rate, the fine GP zone and η′ phase were transformed to be larger η′ and η precipitates. Moreover, continuous η phase at grain boundary was also grown to be individual large precipitates. Cooling aging time was decreased about 90% than that for T6 treatment, indicating cooling aging could improve the mechanical properties, corrosion resistance and production efficiency with less energy consumption.     

Effects of solution treatment on the microstructure and mechanical properties of Al–Cu–Mg–Ag alloy

The effects of solution treatment on the microstructure and mechanical properties of Al–Cu–Mg–Ag alloy were studied by optical microscopy (OM), scanning electron microscopy (SEM), energy dispersive X-ray (EDX), differential scanning calorimeter (DSC), transmission electron microscopy (TEM) and tensile test, respectively. The results show that the mechanical property increases and then decreases with increasing the solution temperature. And the residual phases are dissolved into the matrix gradually, the number fraction of the precipitation and the size of recrystallized grains increase. Compared to the solution temperature, the solution holding time has less effect on the microstructure and the mechanical properties of Al–Cu–Mg–Ag alloy. The overburnt temperature of Al–Cu–Mg–Ag alloy is 525 °C. The yield strength and the elongation get the best when the alloy is solution treated at 515 °C for 1.5 h, is 504 MPa and 12.2% respectively. The fracture mechanism of the samples is ductile fracture.     

Effects of Ca on microstructure, mechanical and corrosion properties and biocompatibility of Mg–Zn–Ca alloys

Zn and Ca were selected as alloying elements to develop an Mg–Zn–Ca alloy system for biomedical application due to their good biocompatibility. The effects of Ca on the microstructure, mechanical and corrosion properties as well as the biocompatibility of the as-cast Mg–Zn–Ca alloys were studied. Results indicate that the microstructure of Mg–Zn–Ca alloys typically consists of primary α-Mg matrix and Ca₂Mg₆Zn₃/Mg₂Ca intermetallic phase mainly distributed along grain boundary. The yield strength of Mg–Zn–Ca alloy increased slightly with the increase of Ca content, whilst its tensile strength increased at first and then decreased. Corrosion tests in the simulated body fluid revealed that the addition of Ca is detrimental to corrosion resistance due to the micro-galvanic corrosion acceleration. In vitro hemolysis and cytotoxicity assessment disclose that Mg–5Zn–1.0Ca alloy has suitable biocompatibility.     

Effects of yttrium and zinc addition on the microstructure and mechanical properties of Mg–Y–Zn alloys

The effects of the yttrium and zinc additions on microstructure and mechanical properties of Mg–Y–Zn alloys were investigated. It was found that the addition of yttrium increases the eutectic temperature of Mg–Y–Zn alloys greatly. The addition of yttrium can also greatly increase the dynamic recrystallization (DRX) temperature of Mg–Y–Zn alloys. The volume fraction of DRX grains in Mg₉₇Y₂Zn₁ alloy is larger than that in Mg₉₆Y₃Zn₁ alloy but smaller than that in Mg_95.5Y₃Zn_1.5 alloy due to the effects of yttrium and zinc addition. The long period stacking (LPS) structures of 18R and 14H were observed in Mg–Y–Zn alloys. The increase in the yttrium content results in increase in strength and decrease in elongation in Mg–Y–Zn alloys. The increase in both yttrium and zinc contents results in increase in both strength and elongation in Mg–Y–Zn alloys. The high strengths of the alloys were thought due to the strengthening by the grain refinement, solid solution strengthening, strain strengthening, high density of plane faults of the LPS structures, and distribution of fine Mg₂₄Y₅ phase.     

The synergic effects of Sc and Zr on the microstructure and mechanical properties of Al–Si–Mg alloy

In order to clarify the possibility of Zr substitution for Sc on the modification of Al-Si casting alloys, the microstructural evolution and tensile properties of Al-Si-Mg based alloys with different combinations of Sc and Zr contents (Sc + Zr = 0.5 wt.%) were systematically investigated. It was found that 0.5 wt.% Sc addition could refine the microstructure significantly and modify the eutectic Si from plate-like morphology to fiber, which promotes the spheroidization of eutectic Si during heat treatment. When Zr was added to partly replace Sc, the microstructure was first further refined, but was then slightly coarsened with increasing Zr content. Moreover, high Zr content was found to decrease its modification on eutectic Si. It was observed that Zr can also concomitantly improve strength and ductility compared with the alloy modified by Sc only. The improvement of mechanical properties was attributed to microstructural refinement, particularly the modification of eutectic Si and precipitation of secondary nano-scale Al₃(Sc_1 − xZr_x) dispersoids.     

Effects of minor Zr and Sr on as-cast microstructure and mechanical properties of Mg–3Ce–1.2Mn–1Zn (wt%) magnesium alloy

The effects of minor Zr and Sr on the as-cast microstructure and mechanical properties of the Mg–3Ce–1.2Mn–1Zn (wt%) alloy were investigated. The results indicate that adding minor Zr and/or Sr to the Mg–3Ce–1.2Mn–1Zn alloy does not cause an obvious change in the morphology and distribution of the Mg₁₂Ce phase. However, the grains of the Zr- and/or Sr-containing alloys are effectively refined. Among the Zr- and/or Sr-containing alloys, the grains of the alloy with the addition of 0.5 wt%Zr + 0.1 wt%Sr are the finest. Furthermore, adding minor Zr and/or Sr to the Mg–3Ce–1.2Mn–1Zn alloy can improve the tensile properties. Among the Zr- and/or Sr-containing alloys, the alloy with the addition of 0.5 wt%Zr + 0.1 wt%Sr obtains the optimum tensile properties. In addition, adding minor Zr and/or Sr to the Mg–3Ce–1.2Mn–1Zn alloy also can improve the creep properties, and the creep properties of the three alloys with the additions of 0.5 wt%Zr + 0.1 wt%Sr, 0.5 wt%Zr, and 0.1 wt%Sr are similar.     

Microstructure development and tensile mechanical properties of Mg–Zn–RE–Zr magnesium alloy

The Mg–5.3 wt.%Zn–1.13 wt.%Nd–0.51 wt.%La–0.28 wt.%Pr–0.79 wt.%Zr alloy prepared by direct chill casting is subjected to hot extrusion. The effects of extrusion ratio and temperature on microstructure and tensile mechanical properties have been studied. The results indicate coarse grains of as-cast alloys are refined with extrusion ratio increasing from 0 to 9. The eutectic constituents are elongated along extrusion direction. However, further increase of extrusion ratio has a little influence on grain refinement and the improvement of mechanical properties of the alloy. Dynamic recrystallisation is the main mechanism of grain refinement during hot extrusion. Raising extrusion temperature results in grain coarsening. Grain shape becomes more equiaxed-like with raising extrusion temperature. At the same time, mechanical properties decrease with the increase of extrusion temperature.