摘要
提升镁合金的高温抗蠕变性能是其能够在汽车动力系统得到广泛应用的关键.对耐热镁合金蠕变变形机制和组织演变缺乏系统研究,是限制其发展的重要因素.本文以低稀土镁合金(Mg-3Sm-0.5Zn-0.4Zr合金)为研究对象,将蠕变应力指数计算、滑移迹线和析出相观察相结合,系统分析了重力铸造和高压铸造Mg-3Sm-0.5Zn-0.4Zr合金在200℃~250℃/60~100 MPa条件下的变形模式和组织演变.主要结果为:重力铸造和高压铸造Mg-3Sm-0.5Zn-0.4Zr合金在200℃/60 MPa条件下稳态蠕变速率分别为1.4×10^(-9)s^(-1)和1.1×10^(-9)s^(-1),表明其具有优异的抗蠕变性能.200°C~250℃/60 MPa条件下,高压铸造合金具有比重力铸造合金更低的稳态蠕变速率.在200℃60~100 MPa条件下,两种合金的主要变形机制均为基面滑移.在225℃条件下,当σ≤80 MPa,基面滑移仍然是两种合金的主要变形模式;当σ>80 MPa,两种合金的变形模式为基面滑移、非基面滑移和孪生.在250℃/60~70 MPa条件下,基面滑移和非基面滑移是两种合金的主要变形模式.此外,重力铸造和高压铸造合金在蠕变过程中均会发生动态析出,形成大量与基面垂直的析出相.与重力铸造合金相比,高压铸造合金具有更多细小的析出相,可有效阻碍位错滑移,这是其具有优异抗蠕变性能的重要因素.
Creep resistance is a crucial requirement for utilizing magnesium in automotive powertrain components.The limited study on creep deformation mechanism and microstructure evolution in creep-resistant magnesium alloys has hindered their industrial applications.In the present work,the creep deformation modes and microstructure evolution under 200℃–250℃/60–100 MPa in Mg-3Sm-0.5Zn0.4Zr alloy produced through permanent mold casting(PMC)and high pressure die casting(HPDC)were investigated via stress exponent(n)calculation,slip trace analysis,together with transmission electron microscopy(TEM)observations.The results indicate that the steady-state creep rates at 200℃/60 MPa were 1.4×10^(−9)s^(−1)for the PMC alloy and 1.1×10^(−9)s^(−1)for HPDC alloy,indicating excellent creep resistance for both.The HPDC alloy exhibited lower steady-stage creep rates than the PMC alloy at 200℃–250℃/60 MPa.At 200℃/60–100 MPa,basal slip was found to be the primary creep deformation mode for both alloys.At 225℃,basal slip dominated creep deformation when stress(σ)was less or equal to 80 MPa,while basal slip,non-basal slip,coupled with twinning accommodated deformation when stress exceeded 80 MPa.At 250℃/60–70 MPa,basal and non-basal slip dominated creep deformation in these two alloys.In addition,dynamic precipitation was observed in both the PMC and HPDC alloys.In comparison to the PMC alloy,the HPDC alloy displayed finer precipitates with increased density,potentially impeding dislocation motion.This characteristic may contribute to the superior creep resistance observed in the HPDC alloy.
作者
夏利红
郑江
王渠东
XIA LiHong;ZHENG Jiang;WANG QuDong(Chongqing Municipal Key Laboratory of Mechanism Design and Control for Manufacturing Equipment,Chongqing Technology and Business University,Chongqing 400067,China;National Engineering Research Centre for Magnesium Alloys,Chongqing University,Chongqing 400044,China;National Engineering Research Center of Light Alloys Net Forming,Shanghai Jiao Tong University,Shanghai 200240,China)
出处
《中国科学：技术科学》
EI
CSCD
北大核心
2024年第6期1079-1090,共12页
Scientia Sinica(Technologica)
基金
国家自然科学基金面上项目(批准号:51575068)资助项目。
关键词
镁合金
高压铸造
蠕变模式
组织演变
动态析出
magnesium alloy
high pressure die casting
creep deformation mode
microstructure evolution
dynamic precipitation
