报告人介绍

王乐耘，材料学院轻合金研究所特别研究员，博士生导师。长期从事金属材料方面的研究，目前主要围绕镁合金强韧化及同步辐射材料表征开展工作，发表学术论文30余篇，总引用数800余次，承担国家自然科学基金面上项目、国家重点研发计划等。 

报告简介 

  Room temperature ductility is a bottleneck for the application of Mg alloys as structural material. Recent studies have shown that the addition of yttrium (Y) and calcium (Ca) can potentially improve Mg’s ductility. Yet, the underlying mechanism is still unclear. For this presentation, we use both synchrotron X-rays and electron microscopy to understand the issue. In the first work, three dimensional X-ray diffraction (3DXRD) was employed to study slip activity in a rolled Mg-3wt%Y alloy sample that was incrementally loaded by tension. At each load step, 3DXRD data was collected to track the deformation of nearly 1000 grains in the probed volume. By analyzing orientation rotation and stress tensor evolution in those grains, it is possible to identify the activated slip systems and measure their critical resolved shear stress (CRSS) values. The result indicates that Y significantly reduces the CRSS ratio between non-basal slip and basal slip. In the second work, tensile testing of an extruded Mg-0.47 wt.% Ca alloy was conducted inside a scanning electron microscope. EBSD-based slip trace analysis was performed to study in-grain slip activities at different strains. While the majority of the grains were deformed by basal slip, prismatic and pyramidal slip were also frequently observed, and their fractions increased with strain. Schmid factor analysis again indicates a relatively low CRSS ratio between non-basal slip and basal slip in this Mg-Ca alloy. The high ductility in Mg-Y and Mg-Ca alloys are thus attributed to the enhanced activity of non-basal slip.