報告題目： Study of the alloying effect on Mg‘s ductility
地    點： 徐祖耀樓313會議室 
時    間： 2019年11月1日（星期五）中午11：30-13：00 
報 告 人： 王樂耘 
報告人介紹： 
  王樂耘，材料學院輕合金研究所特別研究員，博士生導師。長期從事金屬材料方面的研究，目前主要圍繞鎂合金強韌化及同步輻射材料表征開展工作，發表學術論文30余篇，總引用數800余次，承擔國家自然科學基金面上項目、國家重點研發計劃等。 
  報告簡介： 
  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.