Papers by Author: Ren Ju Cheng

Abstract: To investigate the deformation behavior of Mg-X(X=Zn, Y) binary solid solution, the strain-stress curve of crystal cell along [0001] for Mg-1.85at.%X(X=Zn, Y) alloy were simulated using first-principles calculations in this study. The simulation presents directly the critical resolved shear stress for pyramidal plane slip systems for Mg-1.85at.%X(X=Zn, Y) alloy. The results show that the minimum critical resolved shear stress (CRSS) of Mg, Mg-1.85at. %Zn and Mg-1.85at. %Y for pyramidal plane slip systems is 2.24, 2.72, 2.96 GPa respectively.

Abstract: The as-cast microstructures and solidification behaviours of Mg-Zn-Al ternary magnesium alloys with different Zn/Al mass ratios were investigated and compared. The results indicate that, when the Zn/Al mass ratio is less than 2, the alloys are composed of a-Mg and Mg₃₂(Al,Zn)₄₉ phases, and with the increase of the Zn/Al mass ratio, the amount of the second phase gradually decreases and its distribution changes from continuous net to quasti-continuous net. However, when the Zn/Al mass ratio is more than 2, the alloys are composed of a-Mg, Mg₃₂(Al,Zn)49 and MgZn phases, and with the increase of the Zn/Al mass ratio, the amount of the second phase gradually increases and its distribution changes from quasti-continuous net to uniform particles. In addition, the onset and the peak temperatures of the second phase transformation for the alloys with the Zn/Al mass ratio of less than 2, are higher than that of the alloys with the Zn/Al mass ratio of more than 2, which results in the different reactions during the second phase transformation and the different types of the second phase.

Abstract: The as-cast microstructures and mechanical properties of Mg-3Ce-1.2Mn-0.9Sc and Mg-3Ce-1.2Mn-1Zn magnesium alloys were investigated and compared. The results indicate that the as-cast microstructure of Mg-3Ce-1.2Mn-0.9Sc alloy was mainly composed of -Mg, Mg12Ce and Mn2Sc phases, and that the as-cast microstructure of Mg-3Ce-1.2Mn-1Zn alloy was mainly composed of -Mg, Mg12Ce and MgZn phases. In addition, the as-cast tensile and creep properties of Mg-3Ce-1.2Mn-0.9Sc alloy were higher than that of the Mg-3Ce-1.2Mn-1Zn alloy. The difference of the two alloys in as-cast tensile and creep properties may be related to the initial microstructures of the two alloys.

Abstract: The effects of the Al content on the as-cast microstructure and mechanical properties of Mg-xAl-0.7Si based magnesium alloys which contained 1%Zn, 0.25%Mn, 0.4%Sb and 0.25%RE were investigated by optical microscopy(OM), scanning electron microscopy(SEM), X-ray diffraction(XRD) analysis and tensile testing. The results indicated that the effects of the Al content from 6% to 8% on the alloy phase types of the experimental alloys were not obvious, and the as-cast microstructure of the experimental alloys with different Al content were composed mainly of the α-Mg matrix, Mg17Al12 phase, Mg2Si phase and Mg3Sb2 phase. The Chinese script morphology of the Mg2Si phase was very obvious in the experimental alloy with 6%Al. With the increase of Al content from 6% to 8%, the yield strength of the experimental Mg-xA1-0.7Si based alloys at room temperature increased, but the yield strength of the experimental Mg-xA1-0.7Si based alloys at 150 °C decreased.

Abstract: The influence of Al-10.5%Sr master alloy, which is much cheaper than Mg-Sr master alloys, on the as-cast microstructure of the AZ31 alloy was investigated. The research results revealed that the Al-10.5%Sr master alloy produced obvious modification of the as-cast microstructure of the AZ31 alloy, and the modification efficiency increased with the holding time from 0min to 60min and the amount of Sr from 0.01% to 0.1%. Moreover, the results also showed that the Al-10.5%Sr master alloys of different states had different modification efficiency on the as-cast microstructure of the AZ31 alloy. The Al-10.5%Sr master alloys in extrusion deformation state and rapid solidification state had better modification efficiency than the Al-10.5%Sr master alloys received and in heat treatment state, which could be related to the microstructure of the Al-10.5%Sr master alloys with different states.