镁合金凝固过程三维枝晶形貌和生长取向研究进展:三维实验表征和相场模拟
发布时间：2019-05-18 06:02
【摘要】：Mg作为一种典型的hcp结构金属,其枝晶形貌和生长取向受到多种因素的影响,目前针对镁合金中a-Mg枝晶生长模型的描述以及多样性的起源等问题的研究都比较缺乏,基于此,本文综述了本课题组在镁合金凝固微观组织结构三维表征方面取得的研究成果.借助同步辐射X射线微观断层扫描技术以及相场数值模型,研究了镁合金凝固过程中a-Mg(X)枝晶生长选择多样性的形成机理以及固溶合金元素(Al,Ca,Zn和Sn等)、固溶元素含量(溶质浓度)等因素对a-Mg枝晶生长选择和演化的影响.研究结果表明,固溶元素、固溶元素含量等因素都会对镁合金中a-Mg三维枝晶形貌和择优取向产生重要影响.在Mg-Ca和Mg-Al(hcp-fcc)合金中,枝晶倾向于以1120或2245为择优方向生长.在Mg-Sn(hcp-bct)合金中,等轴生长的枝晶沿着基面上1120和偏离基面的112X(X≈2)方向形成一种18次分支的结构,在Mg-Zn(hcp-hcp)合金中,a-Mg枝晶的择优取向会随着Zn含量的增加,从1120方向朝偏离基面的1121方向发生连续转变,并在转变的过渡区,发现了超支化的藻状枝晶结构,其原因可能是高各向异性Zn元素的引入带来的固/液界面自由能各向异性的变化.研究结果从一定程度上揭示了镁合金凝固过程中a-Mg枝晶生长形貌和分支结构选择多样性的规律.同时基于快速X射线成像技术率先开展了镁合金凝固过程三维微观结构演化原位表征研究,获得了镁合金凝固过程三维枝晶的生长演化过程.
[Abstract]:As a typical hcp structural metal, the dendritic morphology and growth orientation of Mg are affected by many factors. At present, there are few studies on the description of a-Mg dendritic growth model and the origin of diversity in magnesium alloys. Based on this, the research results of three-dimensional characterization of solidification microstructure of magnesium alloys in our research group are reviewed in this paper. The formation mechanism of a-Mg (X) dendrite growth diversity and solid solution alloy elements (Al,Ca,Zn and Sn, etc.) during solidification of magnesium alloys were studied by means of synchroradiation X-ray microscopic tomography and phase field numerical model. The effect of solid solution element content (solute concentration) on the growth selection and evolution of a-Mg dendrite. The results show that the content of solid solution elements has an important effect on the morphology and preferred orientation of a-Mg in magnesium alloys. In Mg-Ca and Mg-Al (hcp-fcc) alloys, dendrites tend to grow in the preferred direction of 1120 or 2245. In Mg-Sn (hcp-bct) alloy, the dendites grown on the same axis form an 18th branch structure along the direction of 1120 on the base plane and 112X (X 鈮，
本文编号：2479745
[Abstract]:As a typical hcp structural metal, the dendritic morphology and growth orientation of Mg are affected by many factors. At present, there are few studies on the description of a-Mg dendritic growth model and the origin of diversity in magnesium alloys. Based on this, the research results of three-dimensional characterization of solidification microstructure of magnesium alloys in our research group are reviewed in this paper. The formation mechanism of a-Mg (X) dendrite growth diversity and solid solution alloy elements (Al,Ca,Zn and Sn, etc.) during solidification of magnesium alloys were studied by means of synchroradiation X-ray microscopic tomography and phase field numerical model. The effect of solid solution element content (solute concentration) on the growth selection and evolution of a-Mg dendrite. The results show that the content of solid solution elements has an important effect on the morphology and preferred orientation of a-Mg in magnesium alloys. In Mg-Ca and Mg-Al (hcp-fcc) alloys, dendrites tend to grow in the preferred direction of 1120 or 2245. In Mg-Sn (hcp-bct) alloy, the dendites grown on the same axis form an 18th branch structure along the direction of 1120 on the base plane and 112X (X 鈮，
本文编号：2479745
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