深过冷Co-B合金外源触发形核行为及组织研究  

Exogenously Triggered-nucleation Behavior and Microstructure of Undercooled Co-B Alloys

作　　者：张瑶清 卜凡 张垚君[1,2] 程宇豪 贺一轩 王军 李金山[1] ZHANG Yaoqing;BU Fan;ZHANG Yaojun;CHENG Yuhao;HE Yixuan;WANG Jun;LI Jinshan(State Key Laboratory of Solidification Processing,Northwestern Polytechnical University,Xi'an 710072,China;Center of Advanced Lubrication and Seal Materials,Northwestern Polytechnical University,Xi'an 710072,China)

机构地区：[1]西北工业大学凝固技术国家重点实验室,陕西西安710072 [2]西北工业大学先进润滑与密封材料研究中心,陕西西安710072

出　　处：《铸造技术》2024年第3期300-308,共9页Foundry Technology

基　　金：国家自然科学基金(52104386,52127807);凝固技术国家重点实验室自主课题(2022-TS-08)。

摘　　要：合金的形核机制及其控制方法是凝固理论的重要研究领域之一。触发形核方式可自主控制形核过冷度,对研究形核理论及组织演变具有极大帮助。但熔体具有亚稳性,在实际处理时,外源性杂质引入熔体后将作为触发形核异质点,改变过冷度ΔT和再辉度ΔT_(R),显著影响后续凝固行为,该种现象更为普遍。本文通过玻璃包覆结合循环过热过冷方式,获得两类不同形核模式凝固的Co_(80)B_(20)合金。自发形核模式下,ΔT及ΔT_(R)分别为280和199 K,组织组成为Co/Co_(3)B细小规则共晶。外源性触发形核模式下,ΔT和ΔT_(R)降至122和21 K。组织转变为初生Co枝晶及晶间的Co_(23)B_(6)基体相。外源性杂质将降低f(θ),减小临界形核半径,降低ΔT,使得组织更加不均匀,在实际的熔体处理过程中应予以控制。The nucleation mechanism of alloys and control methods are important research areas for solidification theory.The triggered nucleation method can autonomously control the undercooling degree of nucleation,which is highly useful for studying nucleation theory and microstructure evolution.However,the melt is metastable.In the actual treatment,the introduction of exogenous impurities into the melt will be used as a heteroamorous point for triggered nucleation,changing the undercooling degreeΔT and remelting degreeΔT_(R),and further significantly affecting the subsequent solidification behavior,which is more common.In this paper,two types of Co80B20 alloys solidified via different nucleation modes were obtained by glass coating combined with cyclic superheating and undercooling.In the spontaneous nucleation mode,ΔT andΔT_(R)are 280 and 199 K,respectively,and the microstructure is composed of a fine,regular eutectic Co/Co_(3)B.In the exogenously triggered nucleation mode,ΔT andΔT_(R)decrease to 122 and 21 K,respectively.The microstructure is transformed into primary Co dendrites and intergranular Co_(23)B_(6)matrix phases.Exogenous impurities reduce f(θ),the critical nucleation radius andΔT,increasing the inhomogeneity of the structure,which should be controlled during actual melt treatment.

关 键 词：形核模式 Co-B合金 凝固行为 微观结构 

分 类 号：TG111.4[金属学及工艺—物理冶金]