Effects of holding temperature and time on semi-solid isothermal heat-treated microstructure of ZA84

• 作 者: 杨明波 潘复生 程仁菊 沈佳
• 机 构: College of Materials Science and Engineering Chongqing Institute of Technology,College of Materials
• 出 处: Transactions of Nonferrous Metals Society of China
• 发表日期: 2008年03期
• 关键词: magnesium holding isothermal fabricating subsequent grains heating dispersed fab

The feasibility of fabricating ZA84 magnesium alloy with non-dendritic microstructure by a semi-solid isothermal heat treatment process and the effects of holding temperature and time on the semi-solid isothermal heat-treated microstructure of the alloy were investigated. The results indicate that it is possible to produce ZA84 alloy with non-dendritic microstructure by suitable semi-solid isothermal heat treatment. After being treated at 560-575 ℃ for 120 min, ZA84 magnesium alloy can obtain a non-dendritic microstructure with 14.2%-25.6% liquid fraction and an average size of 56-65 μm of the unmelted primary solid particles. With the increasing holding time from 30 to 120 min or holding temperature from 560 to 575 ℃, the average size of unmelted primary solid particles decreases and globular tendency becomes more obvious. Under the experimental condition, the microstructural evolution of ZA84 alloy during semi-solid isothermal treatment is mainly composed of three stages of initial coarsening, structural separation and spheroidization. The subsequent coarsening of spheroidal grains is not observed.

The feasibility of fabricating ZA84 magnesium alloy with non-dendritic microstructure by a semi-solid isothermal heat treatment process and the effects of holding temperature and time on the semi-solid isothermal heat-treated microstructure of the alloy were investigated. The results indicate that it is possible to produce ZA84 alloy with non-dendritic microstructure by suitable semi-solid isothermal heat treatment. After being treated at 560-575 ° C. for 120 min, ZA84 magnesium alloy can obtain non-dendritic microstructure with 14.2% -25.6% liquid fraction with the increasing holding time from 30 to 120 min or holding temperature from 560 to 575 ° C, the average size of unmelted primary solid particles decreases and the globular tendency becomes more obvious . Under the experimental condition, the microstructural evolution of ZA84 alloy during semi-solid isothermal treatment is mainly composed of three stages of init ial coarsening, structural separation and spheroidization. The subsequent coarsening of spheroidal grains is not observed.