半固态等温处理Mg-Zn-Y合金微观组织演变

Microstructure Evolution of Mg-Zn-Y Alloys during Semi-Solid Isothermal Heat Treatment

摘要:

研究了挤压Mg-2Zn-xY (x=0.5, 1, 2, at%)合金在半固态等温处理过程中的微观组织演变规律。结果表明：3种Mg-2Zn-xY合金中，挤压Mg-2Zn-1Y合金中α-Mg基体晶粒尺寸最小，挤压Mg-2Zn-2Y合金中出现了大量的孪晶；当半固态等温时间为10 min时，随着等温温度的升高，Mg-2Zn-xY合金中α-Mg固相晶粒均逐渐趋于球化，且α-Mg固相颗粒逐渐分离，晶界处的液相和晶内液池体积分数均明显增加；随着580 ℃等温时间的延长（≤30 min），Mg-2Zn-0.5Y合金微观组织演变以Ostwald熟化机制为主，而Mg-2Zn-1Y和Mg-2Zn-2Y合金微观组织演变过程中Ostwald熟化机制和固相颗粒熔化机制同时起主导作用

Abstract:

Microstructure evolution of extruded Mg-2Zn-xY (x=0.5, 1, 2, at%) alloys in semi-solid isothermal heat treatment process was investigated. The results show that in these three kinds of Mg-2Zn-xY alloys, α-Mg grain size of extruded Mg-2Zn-1Y alloy is the minimum, and a large number of twins are found in extruded Mg-2Zn-2Y alloy. When the semi-solid isothermal time is 10 min, with increasing temperature, α-Mg solid phase grains in Mg-2Zn-xY alloy are gradually spheroidized, and separated by liquid phases. Otherwise, the liquid phase contents located both at the grain boundaries and in the grain interior significantly increase. With the increase of isothermal time (≤30 min) at 580 °C, Ostwald ripening mechanism acts a major role during microstructure evolution of semi-solid Mg-2Zn-0.5Y alloy. However, both Ostwald ripening mechanism and solid particle melting mechanism act major roles at the same time during microstructure evolution of semi-solid Mg-2Zn-1Y and Mg-2Zn-2Y alloys