铸态Mg−2Sc−2Y−0.5Zr合金热压缩行为及热加工图

Hot Compression Behavior and Processing Map of As-cast Mg-2Sc-2Y-0.5Zr Alloy

目的研究铸态合金Mg−2Sc−2Y−0.5Zr合金热压缩行为及热加工图,根据合金的用途和再结晶程度,确定最佳热加工艺参数,为合金后续变形提供参考。方法通过实验设计合金成分,称取一定质量的纯镁锭和二元中间合金,在真空熔炼炉中加热至760℃,保温至熔化,搅拌,静止,然后在钢磨具中空冷,得到合金锭。实际成分通过电感耦合等离子体原子发射光谱法测定;切取合适大小的铸锭进行X射线衍射实验。用于热压缩的铸态样品为圆柱形试样(ϕ10 mm×15 mm),在进行热压缩实验前,对所有样品表面进行抛光。使用Gleeble−3800热压缩模拟试验机对铸态Mg−2Sc−2Y−0.5Zr合金进行热压缩试验,变形温度为573~723 K,应变速率为0.001~1 s^(-1)。经热压缩后将各试样立即进行水淬,以保持压缩变形组织。将压缩样品沿着纵轴切割压缩样品,然后抛光、蚀刻,并使用扫描显微镜进行检查,以观察微观结构的演变,计算该合金的变形激活能,并构建合金高温变形的本构方程,建立真应变为0.5时的热加工图。结果得到了铸态Mg−2Sc−2Y−0.5Zr合金热变形本构方程及真应变为0.5时的热加工图,合金热变形发生了动态回复和动态再结晶,合金的热变形激活能Q为198.58 kJ/mol。结论根据用途和再结晶程度,铸态Mg−2Sc−2Y−0.5Zr合金的最佳加工参数为变形温度623~673 K、应变速率0.001~0.01 s^(-1),以及变形温度723 K、应变速率0.001~1 s^(-1)。

The work aims to study the hot compression behavior and hot processing map of the as-cast Mg-2Sc-2Y-0.5Zr alloy,and determine the best hot processing parameters according to the purpose and recrystallization degree of the alloy,so as to provide reference for the subsequent deformation of the alloy.The alloy composition was designed according to the experiment and a certain amount of pure magnesium ingot and binary master alloy were weighed and put in the vacuum melting furnace.They were heated to 760℃in a vacuum melting furnace and then kept at this temperature until melting.Next,they were stirred and kept static,and then cooled naturally in the steel grinder to obtain alloy ingot.The actual composition was determined by inductively coupled plasma atomic emission spectrometry.The ingot with appropriate size was cut for X-ray diffraction experiment.The as-cast sample used for thermal compression was a cylindrical sample(ϕ10 mm×15 mm).The surface of all samples was polished before the thermal compression test.The hot compression test of as-cast Mg-2Sc-2Y-0.5Zr alloy was carried out with a Gleeble-3800 hot compression simulation tester under the condition of deformation temperature of 573-723 K and strain rate of 0.001-1 s^(-1).After hot compression,each sample was quenched with water immediately to maintain the compression deformation structure.The compressed sample was cut along the longitudinal axis,polished,etched and inspected with a scanning microscope to observe the evolution of the microstructure,calculate the deformation activation energy of the alloy,construct the constitutive equation of the alloy for high temperature deformation,and establish the hot working diagram when the true strain was 0.5.The results showed that the constitutive equation of hot deformation of as-cast Mg-2Sc-2Y-0.5Zr alloy and the hot processing diagram at the true strain of 0.5 were obtained.Dynamic recovery and dynamic recrystallization occurred during hot deformation of the alloy.The activation energy of hot deformation of the alloy was 198.58 kJ/mol.It is concluded that the best processing parameters of as-cast Mg-2Sc-2Y-0.5Zr alloy according to the purpose and the degree of recrystallization are 623-673 K,0.001-0.01 s^(-1) and 723 K,0.001-1 s^(-1).