Influence of hexagonal to orthorhombic phase transformation on diffusion-controlled dendrite evolution in directionally solidified Sn−Ni peritectic alloy  

六方−正方相变对定向凝固Sn−Ni包晶合金中扩散控制的枝晶演化的影响

作　　者：Peng PENG Bi-zhou ZHAO Jia-tai WANG Xing PEI Zi-jie LIU Lu GAN Sheng-yuan LI 彭鹏;赵弼洲;王甲泰;裴兴;刘子杰;甘露;李升渊(兰州大学材料与能源学院,兰州730000;青海师范大学物理与电子信息学院,西宁753000;甘肃省中医院,兰州730000)

机构地区：[1]School of Materials and Energy,Lanzhou University,Lanzhou 730000,China [2]School of Physics and Electronic Information Engineering,Qinghai Normal University,Xining 753000,China [3]Gansu Provincial Hospital of Traditional Chinese Medicine,Lanzhou 730000,China

出　　处：《Transactions of Nonferrous Metals Society of China》2022年第5期1728-1740,共13页中国有色金属学报（英文版）

基　　金：the support from the Natural Science Foundation of China(No.51871118);Open Project of Key Laboratory for Magnetism and Magnetic Materials of the Ministry of Education,Lanzhou University,China(No.LZUMMM2021005);the Science and Technology Project of Lanzhou City,China(No.2019-1-30);State Key Laboratory of Special Rare Metal Materials,China(No.SKL2020K003)。

摘　　要：The hexagonal to orthorhombic(HO)transformation fromβ-Ni_(3)Sn_(2)(hexagonal)phase toα'-Ni_(3)Sn_(2)(orthorhombic)phase was confirmed in directionally solidified Sn−Ni peritectic alloys.It is shown that the remelting/resolidification process which is caused by both the temperature gradient zone melting(TGZM)and Gibbs−Thomson(G−T)effects can take place on secondary dendrites.Besides,the intersection angle between the primary dendrite stem and secondary branch(θ)is found to increase fromπ/3 toπ/2 as the solidification proceeds.This is the morphological feature of the HO transformation,which can change the diffusion distance of the remelting/resolidification process.Thus,a diffusion-based analytical model is established to describe this process through the specific surface area(S_(V))of dendrites.The theoretical prediction demonstrates that the remelting/resolidification process is restricted when the HO transformation occurs during peritectic solidification.In addition,the slope of the prediction curves is changed,indicating the variation of the local remelting/resolidification rates.在定向凝固Sn−Ni包晶合金中发现六方−正方相变,即自β-Ni_(3)Sn_(2)(六方)向α'-Ni_(3)Sn_(2)(正方)相的转变。研究表明,二次枝晶臂上发生由温度梯度区域熔化(TGZM)与吉布斯−汤姆森(G−T)效应引起的重熔/再凝过程。此外,一次枝晶干与二次分枝间夹角(θ)随凝固过程进行由π/3增至π/2,这一现象为六方−正方转变的组织特征,并会改变重熔/再凝过程中的扩散距离。因此,建立扩散控制唯象模型,重熔/再凝过程由枝晶的比表面积(S_(V))进行表征。模型预测表明,包晶凝固过程中发生六方−正方相变后可抑制重熔/再凝过程。另外,预测曲线的斜率变化表明重熔/再凝过程局域速率发生改变。

关 键 词：directional solidification dendritic solidification peritectic microstructures Gibbs−Thomson effect temperature gradient zone melting HO transformation 

分 类 号：TG131[一般工业技术—材料科学与工程]