Effect of rolling reduction on deformation mechanism and twinning behavior of WE43 magnesium alloy

The effect of rolling reduction of the last pass on the dislocation slip and twinning behavior during direct hot rolling of a cast WE43 magnesium alloy at 480℃ was investigated.The results showed that prismatic<á>slip was always the main deformation mode during rolling at 480℃.In addition,the activated twinning type was associated with rolling reduction.The{1012}extension twinning was activated at a slight rolling reduction(2%),while{1011}compression twinning and{1011}−{1012}double twinning were activated at larger rolling reduction(12%and 20%).Schmid factor calculation showed that the activation of{1012}extension twin variants followed the Schmid Law,whereas the activation of{1011}compression twin variants did not follow it.Even if the rolling reduction reached 20%,almost no dynamic recrystallization(DRX)grains were found,presumably because the amount of deformation required for DRX to occur was not reached.

Effect of Solution Treatment on the Microstructure and Mechanical Properties of Sand-Cast Mg–9Gd–4Y–0.5Zr Alloy

Sand-cast Mg–9Gd–4Y–0.5 Zr（wt%） alloy was solution-treated at 500–565 ℃ in the time range of 0.5–30 h in air or vacuum to investigate its microstructure evolution and mechanical properties. The results showed that solution treatment temperature had a significant influence on the dissolving rate of eutectic phase and grain growth. Taken both of them into consideration, 510–520 ℃ was considered to be the optimum solution treatment temperature range for this alloy.It should be noted that the trace（0.4–0.9 vol%） and insoluble cuboid-shaped phase precipitated during solution treatment was identified to be YH2, of which the hydrogen was thought to come from both the melting and solution heating process.In addition, the 3D morphology and dissolving process of Mg24（Gd,Y）5 eutectic phases in the as-cast alloy were also discussed via in-situ observation under X-ray tomography.

Effects of Zinc and Calcium Concentration on the Microstructure and Mechanical Properties of Hot-Rolled Mg–Zn–Ca Sheets

Four kinds of Mg alloys with different Zn and Ca concentration were selected to analyze the effect of Zn and Ca concentration on the microstructure and the mechanical properties of Mg-Zn-Ca alloys. It was found that Zn and Ca concentration has a great influence on the volume fraction, the morphology and the size of second phase. The Mg-1.95Zn- 0.75Ca （wt%） alloy with the highest volume fraction, continuous network and largest size of Ca2Mg6Zn3 phase showed the lowest elongation to failure of about 7%, while the Mg-0.73Zn-0.12Ca （wt%） alloy with the lowest volume fraction and smallest size of Ca2Mg6Zn3 phase showed the highest elongation to failure of about 37%. It was suggested that uniform elongations of the Mg-Zn-Ca alloys were sensitive to the volume fraction of the Ca2Mg6Zn3 phases, especially the network Ca2Mg6Zn3 phases; post-uniform elongations were dependent on the size of the Ca2Mg6Zn3 phase, especially the size of network Ca2Mg6Zn3 phase. Reduction in Zn and Ca concentration was an effective way to improve the room- temperature ductility of weak textured Mg-Zn-Ca alloys.

Effects of Sb Content on Solidification Pathways and Grain Size of AZ91 Magnesium Alloy

The phase constitution and solidification pathways of AZ91＋xSb（x = 0, 0.1, 0.5, 1, in wt%） alloys were investigated through ways of microstructure observation, thermal analysis technique, and thermodynamic calculation. It was found that the non-equilibrium solidification microstructure of AZ91＋xSb（x = 0.1, 0.5, 1） is composed of a-Mg matrix, b-Mg17Al12 phase, and intermetallic compound Mg3Sb2. The grain size of the alloys with different Sb contents was quantitatively determined by electron backscattered diffraction technique which shows no grain refinement in Sb-containing AZ91 alloy. Thermodynamic calculations are in reasonable agreement with thermal analysis results, showing that the Mg3Sb2 phase forms after a-Mg nucleation, thus impossible acts as heterogeneous nucleus for a-Mg dendrite. Besides,the solid fraction at dendrite coherency point（fDCPs） determined from thermal analysis decreases slightly with increasing Sb content, which is consistent with the fact that Sb does not refine the grain size of AZ91 alloy.