摘要
在不同凝固阶段合金的半固态组织和脉冲电流热效应的实验研究基础上,探讨了低压脉冲电流下AZ91D镁合金半固态组织的形成机制。结果表明:在合金的液相线以下开始脉冲放电,二次枝晶臂分离需要较长的时间,一次枝晶臂难以球化;从合金的液相线以上开始脉冲放电,不会析出粗大的枝晶,二次枝晶臂分离比较容易。脉冲电流降低了半固态合金的冷却速度,同时造成了合金熔体强烈的温度起伏;随着脉冲电压的增加,半固态合金的冷却速度逐渐减小,熔体的瞬时平均温升逐渐增加。初始形核率的提高和二次枝晶臂的根部熔断是低压脉冲电流下球状或颗粒状初生α-Mg形成的重要机制。
Based on the experimental study of semi-solid microstructure of magnesium alloy AZ91 D at different stages of solidification and heat generation of electric current pulses, the formation mechanism of semi-solid microstructure of the alloy treated by low-voltage electric current pulses（LVECP） discharge was discussed. The results show that it takes a long time for the secondary arm to detach from the dendrite and the spheroidization of primary dendritic arm is difficult when the discharge starts below the liquidus temperature. The primary α-Mg phase particles are not well developed and it is easy for the main trunks to lose secondary arms when the discharge starts above the liquidus temperature. Heat generation caused by discharge decreases the cooling rate of the melt and causes temperature fluctuation in the melt. With the increase of discharging voltage, the cooling rate of the alloy decreases, but the maximal temperature fluctuation of the alloy increases gradually. The increase of nucleation and the root remelting of the secondary dendrite arms are important formation mechanisms of the spherical primary α-Mg phase in semi-solid slurry of magnesium alloy AZ91 D treated by LVECP discharge.
出处
《稀有金属材料与工程》
SCIE
EI
CAS
CSCD
北大核心
2015年第3期665-670,共6页
Rare Metal Materials and Engineering
基金
国家自然科学基金资助项目(51261026)
航空科学基金资助项目(20125356009)
关键词
低压脉冲电流
半固态组织
镁合金
形成机理
low-voltage electric current pulses
semi-solid microstructure
magnesium alloy
formation mechanism
