静电悬浮条件下液态Zr_(60)Ni_(25)Al_(15)合金的热物理性质与快速凝固机制  

Thermophysical properties and rapid solidification mechanism of liquid Zr_(60)Ni_(25)Al_(15)alloy under electrostatic levitation condition

作　　者：金英捷 耿德路 林茂杰 胡亮[1] 魏炳波[1] Jin Ying-Jie;Geng De-Lu;Lin Mao-Jie;Hu Liang;Wei Bing-Bo(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：《物理学报》2024年第8期287-295,共9页Acta Physica Sinica

基　　金：国家重点研发计划(批准号:2021YFA0716301);国家自然科学基金(批准号:52088101,52174378)资助的课题.

摘　　要：采用静电悬浮实验技术测定了液态Zr_(60)Ni_(25)Al_(15)合金的热物理性质,并研究了其深过冷快速凝固过程.实验发现,液态合金所获得的最大过冷度可达316 K(0.25TL),其密度和表面张力与温度呈线性关系,而黏度则随温度呈指数变化.当过冷度小于259 K时,凝固过程中发生两次再辉现象,分别对应着二相(Zr_(6)Al_(2)Ni+Zr_(5)Ni_(4)Al)共晶和三元(Zr_(6)Al_(2)Ni+Zr_(5)Ni_(4)Al+Zr_(2)Ni)共晶的快速生长.若过冷度超过259 K,凝固过程只发生一次再辉,3个化合物相均可从合金熔体中独立形核,形成三元不规则共晶组织.理论计算和实验表明,小过冷时Zr_(6)Al_(2)Ni相优先形核,而当过冷度足够大时,三相能够同时形核.In this study,the thermophysical properties and rapid solidification mechanism of highly undercooled liquid Zr_(60)Ni_(25)Al_(15) alloy are investigated through the electrostatic levitation technique.The maximum undercooling of this alloy reaches 316 K(0.25TL).Both density and surface tension display a linear relationship with temperature,while viscosity is related to temperature exponentially.When alloy undercooling is less than 259 K,two significant recalescence events are observed during solidification,corresponding to the formation of pseudobinary(Zr_(6)Al_(2)Ni+Zr_(5)Ni_(4)Al)eutectic and ternary(Zr_(6)Al_(2)Ni+Zr_(5)Ni_(4)Al+Zr_(2)Ni)eutectic.The growth velocity of the binary eutectic phase gradually increases with further undercooling and reaches a maximum undercooling value of 259 K.In contrast,once undercooling exceeds 259 K,a single recalescence event occurs,leading to the independent nucleation of all three compound phases from alloy melt and the rapid growth of a ternary anomalous eutectic structure.Notably,the growth velocity of the ternary eutectic phase exhibits a gradual decline with further undercooling.This diminishing trend of the growth velocity suggests that further undercooling might entirely suppress crystal growth dynamically at a threshold of 385 K.With classical nucleation theory and the Kolmogorov-Johnson-Mehl-Avrami(KJMA)model,the onsets of crystallization for the three phases are calculated,thereby constructing a time-temperature-transformation(TTT)diagram.This diagram elucidates the competitive nucleation among the three phases in the undercooled melt.Both theoretical and experimental evidence reveal that Zr_(6)Al_(2)Ni phase is primarily nucleated at lower undercooling levels,whereas under higher cooling condition,it is possible for all three phases to nucleate simultaneously.

关 键 词：静电悬浮 液态金属 快速凝固 共晶生长 

分 类 号：TG139.8[一般工业技术—材料科学与工程]