摘要
CrCoNiSi_(0.3)中熵合金在准静态加载下展现出优异的强韧协同力学行为,温度和应变率对合金力学行为的影响亟待研究。通过霍普金森压杆装置,对CrCoNiSi_(0.3)中熵合金进行了室温(20℃)动态压缩(1776~5196 s^(−1))实验和高温(20~1000℃)准静态压缩实验,系统研究了CrCoNiSi_(0.3)中熵合金在不同应变率和温度下的力学行为和变形机理。结果表明:在动态加载下,CrCoNiSi_(0.3)中熵合金的屈服强度随着应变率的升高而增大,表现出较高的应变率敏感性,该现象源于随着应变率增大而增加的层错、变形孪晶和面心立方到密排六方相变;平均应变硬化率随着应变率的升高先略有上升,当应变率达到约5196 s^(−1)时,由于剪切带形成,平均应变硬化率下降。随着温度的升高,压缩屈服应力和应变硬化能力下降,但直至1000℃仍未表现出明显的应变软化现象;在600℃下合金有高密度层错和位错锁,表现出与400℃时基本一致的屈服强度和流动应力。针对应变硬化随应变率升高而降低的力学行为,在模型中引入应变硬化函数,建立了修正的Johnson-Cook本构模型,该模型可以较好地预测CrCoNiSi_(0.3)中熵合金的力学行为。
The CrCoNiSi_(0.3) medium entropy alloy exhibits excellent synergistic mechanical behavior of strength and toughness under quasi-static loading.However,the influences of temperature and strain rate on the mechanical behavior of the alloy urgently need to be studied.Through the split Hopkinson pressure bar(SHPB),dynamic compression experiments at room temperature(20℃)with strain rates ranging from 1776 s^(−1) to 5196 s^(−1) and quasi-static compression experiments at high temperatures(from 20℃ to 1000℃)were carried out on the CrCoNiSi_(0.3) medium entropy alloy.The strain rate and temperature-dependent mechanical behavior and deformation mechanism of the CrCoNiSi_(0.3) medium entropy alloy were systematically investigated.The results show that under dynamic loading,the yield strength of the CrCoNiSi_(0.3) medium entropy alloy increases with the increase of the strain rate,exhibiting a high strain rate sensitivity.This is attributed to the comprehensive mechanism of stacking faults,deformation twins,and the phase transformation from face-centered cubic to hexagonal close packed,which increase as the strain rate increases.The average work hardening rate increases slightly at first with the increase of the strain rate.When the strain rate reaches about 5196 s^(−1),the average work hardening rate decreases due to the formation of shear bands.As the temperature rises,the compressive yield stress and work hardening ability of the alloy gradually decrease.However,there is still no work softening phenomenon at a temperature of 1000℃.Due to the high density of stacking faults and dislocation locks in the alloy at 600℃,it shows almost the same yield strength and flow stress as at 400℃.Aiming at the mechanical behavior that the strain hardening shows a decrease with the increase of the strain rate,a strain hardening function was introduced into the model,and a modified Johnson-Cook constitutive model was established,which can predict the mechanical behavior of the CrCoNiSi_(0.3) medium entropy alloy quite well.
作者
郜林玉
杜时雨
常慧
张团卫
王志华
GAO Linyu;DU Shiyu;CHANG Hui;ZHANG Tuanwei;WANG Zhihua(Institute of Applied Mechanics,College of Aeronautics and Astronautics,Taiyuan University of Technology,Taiyuan 030024,Shanxi,China;Shanxi Key Laboratory of Material Strength and Structural Impact,Taiyuan University of Technology,Taiyuan 030024,Shanxi,China)
出处
《高压物理学报》
北大核心
2025年第9期1-15,共15页
Chinese Journal of High Pressure Physics
基金
国家自然科学基金(12102291,12225207,12072220,12302480)
山西省科技创新人才团队专项(202204051002006)。
关键词
中熵合金
力学行为
应变率
应变硬化
变形机理
medium entropy alloy
mechanical behavior
strain rate
strain hardening
deformation mechanism
作者简介
郜林玉(2001-),女,硕士研究生,主要从事新型中/高熵合金的冲击力学行为研究.E-mail:gaolinyu001@163.com;通信作者:杜时雨(1995-),女,博士,主要从事新型中/高熵合金的冲击力学行为与绝热剪切行为研究.E-mail:dsytyut@163.com。
