Nb_(42)Ti_(21)Co_(37)包共晶合金定向凝固组织演化规律  

Evolution Law of Directional Solidification Structure for Nb_(42)Ti_(21)Co_(37)Ternary Quasi-peritectic Alloy

作　　者：王金华 闫二虎 狄翀博 陈运灿 刘威 王豪 葛晓宇 程健 黄仁君 孙立贤[1] Wang Jinhua;Yan Erhu;Di Chongbo;Chen Yuncan;Liu Wei;Wang Hao;Ge Xiaoyu;Cheng Jian;Huang Renjun;Sun Lixian(Guangxi Key Laboratory of Information Materials,Guilin University of Electronic Technology,Guilin 541004,China)

机构地区：[1]桂林电子科技大学广西信息材料重点实验室,广西桂林541004

出　　处：《稀有金属材料与工程》2021年第10期3577-3584,共8页Rare Metal Materials and Engineering

基　　金：国家自然科学基金(51761009,51701048);广西自然科学基金(2020GXNSFAA159163);桂林电子科技大学研究生教育创新计划(2019YCXS109);广西信息材料重点实验室基金(191021-Z)。

摘　　要：包共晶转变兼具共晶转变和包晶转变双重特征,存在于众多的工业合金中。然而,迄今为止尚未建立起相对完整的包共晶凝固理论模型,关于其凝固机理的相关研究较少。基于此,本研究针对Nb_(42)Ti_(21)Co_(37)包共晶合金开展了不同抽拉速度(V=1,3,5,15,30,70μm/s)下的定向凝固实验,旨在研究不同抽拉速度下合金的微观组织演化规律,并构建相应的凝固机制。结果表明:Nb_(42)Ti_(21)Co_(37)包共晶合金常规铸态和定向凝固组织中均含有α-Nb、Co_(6)Nb_(7)和TiCo+Co_(6)Nb_(7)包共晶相。随着抽拉速度的逐渐增加,初生相α-Nb依次经历了圆球状→花瓣状→团簇状→枝晶状的转变;伴随着上述过程,淬火界面经历了胞状界面到胞枝晶状界面的转变,并且,在抽拉速度V=70μm/s时固/液界面消失。其次,定向凝固稳态生长区内包共晶的组织逐渐细化,其层间距(λ)与抽拉速度呈指数线性关系,即λ=1+5e^(2.5V)。当抽拉速度低于5μm/s时,合金的定向凝固过程与平衡凝固相类似;另外,各相在稳定生长区的生长机制为共生生长,随着抽拉速度的增加,包共晶组织的定向排列性逐渐变差。The quasi-peritectic transformation,which has the dual characteristics of eutectic and peritectic reaction,exists in many industrial alloys.However,a relatively complete theoretical model of this transformation has not been established so far,and there are few related studies on its solidification mechanism.Given this,the directional solidification experiments at different drawing speeds(V=1,3,5,15,30,70μm/s)for the Nb_(42)Ti_(21)Co_(37)quasi-peritectic alloy were carried out,aiming to study the evolution law of directional solidification structure at different speeds and explore the corresponding solidification mechanism.The results show that theα-Nb,Co_(6)Nb_(7) and TiCo+Co_(6)Nb_(7) quasi-peritectic phases exist in the conventional as-cast and directional solidification structures of Nb_(42)Ti_(21)Co_(37)quasi-peritectic alloy.With the gradual increase of the drawing speed,the primaryα-Nb phase undergoes a transformation of spherical shape→petal-like→cluster-like→dendrite-like.During the above process,the quenched interface undergoes the transformation from cellular-like interface to cellular dendrite-like interface,and the corresponding solid/liquid interface disappears when the drawing speed is equal to 70μm/s.Secondly,the quasi-peritectic structure in the steady-state growth zone of directional solidification gradually refines,and an exponential linear relationship of the quasi-peritectic interphase spacing versus the drawing speed,i.e.λ=1+5e^(2.5V),appears for the directionally solidified samples.When the drawing speed is lower than 5μm/s,the directional solidification process is near-equilibrium conditions,and the growth mechanism of each phase in the stable growth zone is symbiotic growth.With the increase of the drawing speed,the directional arrangement of the quasi-peritectic structure gradually deteriorates.

关 键 词：Nb-Ti-Co合金 定向凝固 微观组织 凝固机制 

分 类 号：TG111.4[金属学及工艺—物理冶金] TG146.416[金属学及工艺—金属学]