Al-Mg合金中层错和孪晶形变能的第一性原理研究

来源期刊：金属学报2011年第5期

论文作者：董明慧 韩培德 张彩丽 杨艳青 张莉莉 李洪飞

文章页码：573 - 577

关键词：第一性原理； 层错能； 孪晶； Al-Mg合金

Key words：first-principles； stacking fault energy； twin； Al-Mg alloy

摘    要：通过基于密度泛函理论(DFT)的第一性原理计算了纯金属Al和Al Mg合金在(111)[112]滑移系的层错能和孪晶形变能,分析了Mg含量、占位对层错能和孪晶形变能的影响.计算选用了局域密度近似(LDA)和广义梯度近似(GGA PW91)2种近似方法,发现GGA PW91所获得的层错能与实验结果符合较好,研究结果表明,纯Al的层错能高于孪晶形变能,随着孪晶层厚度的增加孪晶形变能略有提高,6层呈完全镜面对称孪晶有的孪晶形变能最低:Mg含量增加使Al-Mg合金的层错能、变形孪晶形变能明湿降低;Mg在Al-Mg合金中占位对结合能和形成热的影响很小,当Mg处于层错层时略使层错能和孪晶形变能提高.

Abstract: By using first-principles method based on the density functional theory (DFT), the stacking fault energy (SFE) and deformation twin energy(DTE)for the (111)[112] slip system of pure Al metal and Al-Mg alloys were investigated.The dependence of these SFE and DTE on solid-solution Mg content and its accupation were specifically analyzed.Two major approximations were made in the process of calculation,which were local density approximation(LDA)and generalized gradient approximation (GGA-PW91),respectively.The calculated SFE values by using GGA-PW91 exhibit an excellent agreement with corresponding experimental measurements.For pure Al metal,the calculated SFE values are greater than those of DTE.Moreover,it is found that under the same deformation conditions,the DTE in pure Al and Al-Mg alloys increase monotonically with the increase of deformation twin thickness.In addition,the calculated results shows that 6-layer twin possesses the lowest DTE,which is probably due to its mirror symmetry structure.Also noteworthy, our calculations reveal a noticeable decreased tendency of SFE and DTE with Mg content increasing,while Mg occupying on stacking fault and twin boundary most likely increases SFE and DTE.There are no considerably detected effects of Mg atomic occupancy variation in Al-Mg alloy on its cohesive energy and formation energy.