无容器微重力条件下Mo-Ni合金熔体的快速凝固与物理性能研究  

Rapid solidification and physical properties of a refractory Mo-Ni alloy under containerless microgravity condition

作　　者：赵晓蕾 王伟丽[1] 沙莎 燕鹏旭 魏炳波[1] ZHAO XiaoLei;WANG WeiLi;SHA Sha;YAN PengXu;WEI BingBo(School of Physical Science and Technology,Northwestern Polytechnical University,Xi’an 710072,China)

机构地区：[1]西北工业大学物理科学与技术学院,西安710072

出　　处：《中国科学：技术科学》2021年第9期1127-1134,共8页Scientia Sinica(Technologica)

基　　金：国家自然科学基金(批准号:52088101)资助项目。

摘　　要：本文采用自由落体技术模拟空间环境条件,实现了液滴直径144~1530µm的Mo-48%Ni合金的微重力快速凝固与组织调控.理论计算表明,液态合金的冷却速率和过冷度均随液滴直径减小而指数增大,分别可达2.41×10^(4) Ks^(−1)和322 K(0.19 T_(L)).实验发现,快速凝固组织由初生NiMo枝晶和(Ni+NiMo)共晶构成,急冷条件抑制了后续固态相变.随着液滴冷速和过冷度增大,粗大的NiMo枝晶逐渐细化,溶质Ni含量呈现先减小再增大的变化趋势;共晶形貌由规则层片转变为非规则组织,其中溶质Mo的含量先增大再减小.初生相和共晶组织的弹性模量均单调递减;初生相显微硬度先缓慢增大后减小,共晶组织显微硬度整体呈现出递减的规律.同时,合金磁化强度减小,但其矫顽力增大,耐温性能得到显著提升.The solidification kinetics and physical properties of Mo-48%Ni alloy were studied using the free fall technique.The cooling rate and undercooling of this alloy both increased exponentially as the droplet diameter decreased,and they could reach 2.41×10^(4)Ks^(−1) and 322 K(0.19 T_(L)),respectively.The high cooling rate significantly suppressed the subsequent solid state transformation process.The primary NiMo phase exhibited a morphological transition from coarse dendrite to a remarkably refined structure,and the regular lamellar(Ni+NiMo)eutectics changed into anomalous eutectic.The maximum length of the primary NiMo phase fell from 142.2 to 28.4μm,whereas its volume fraction initially rose and then fell,with a maximum of 60.1%.Moreover,the variation in the Mo content of the primary phase coincided well with that of the eutectic structure.As regards mechanical properties,the nanoindentation measurements indicated that the elastic moduli of the primary phase and the eutectic structure both showed a downward trend along with the microstructure evolution.The eutectic hardness decreased monotonously from 14.1 to 8.7 GPa,whereas the primary phase hardness increased slightly from 8.0 to 8.5 GPa and finally fell to 5.4 GPa.In addition,the growth morphology of the(Ni)solid solution within the eutectic structure was shown to have an obvious effect on the magnetic properties of the Mo-48%Ni alloy.As the rate of cooling increased,the saturation magnetization and residual magnetization diminished.The alloy’s coercivity increased from 11.8 to 25.7 A m^(−1),indicating enhancement of the temperature resistance induced by microstructure refinement.The rapid solidification under space simulation conditions affected the mechanical and magnetic properties of the Mo-48%Ni alloy to a certain degree.

关 键 词：深过冷 快速凝固 难熔合金 力学性能 磁学性能 

分 类 号：TG146.412[一般工业技术—材料科学与工程]