The team of Professor Dong Jie of the National Engineering Research Center for Light Alloy Precision Forming of Shanghai Jiaotong University and the team of Professor Dierk Raabe of the Max-Planck Institute for Steel and Iron have made important progress in the research of the interaction mechanism between magnesium alloy twins and the second phase. "On the interaction of precipitates and tensile twins in magnesium alloys" was published in Acta Materialia, a top academic journal in the field of international metal materials.
The link to the paper is: https://www.sciencedirect.com/science/article/pii/S135964541930494X
The close-packed hexagonal crystal structure magnesium alloy includes a variety of deformation modes such as basal, cylindrical, conical sliding and stretching, compression, secondary twinning and untwisting, and the interaction between these deformation modes and grain boundaries and the second equal The role is complex. Therefore, studying these interaction mechanisms on the mesoscopic scale is of great significance to enhance and regulate the strength and toughness of magnesium alloys.
In this paper, a self-developed full-scale plastic-phase field coupling model of a magnesium alloy polycrystal is used to systematically and visually simulate the interaction mechanism between tensile twins and the second phase in a magnesium alloy. The influence of the orientation, size, volume fraction, and morphology (aspect ratio) of the two phases on the critical shear stress of twin growth. On the mesoscopic scale, the relationship between deformation mode, microstructure and macro performance is established.
It is found that the interaction between twins and the second phase will cause local dislocation slip plasticity behavior, and at the same time excite basal plane, cylindrical surface and cone plane dislocation, but the basal plane slip plastic zone is much larger than the non-basal plane plastic zone. The non-uniform stress field caused by the interaction of twins with the second phase and a large number of activated dislocations in the matrix will increase the critical shear stress of subsequent twin growth. High volume fraction, small size, high aspect ratio, non-shearing flakes and other second relatively hindering twin growth are most effective, and can effectively reduce the critical shear stress between tensile twins and non-basal plane dislocations. Ratio, which can increase the strength of the magnesium alloy and improve the plastic anisotropy.