快速凝固/粉末冶金Mg-6wt%Zn热挤压合金的微观组织与力学性能研究

Investigation on Microstructure and Mechanical Properties of Rapidly Solidified / Powder Metallurgy Mg-6wt%Zn Alloy

采用雾化-双辊急冷法制备出快速凝固Mg-6wt%Zn合金薄片及片状粉末,随后通过热挤压工艺制备了RS/PM Mg-6Zn镁合金棒材,并对热挤压合金的微观组织、物相种类及室温、高温力学性能进行了研究。结果表明,经过热挤压后,快速凝固Mg-6Zn合金的微观组织进一步细化,晶粒尺寸为1～2μm,同时合金中析出大量的细小弥散相,并具有较高的位错密度,合金的相组成为α-Mg和Mg51Zn20及少量的Mg2Zn3相,与快速凝固状态下相似。室温下,合金的抗压强度接近300 MPa。但随着温度的升高,合金的强度大幅度降低,其主要原因是高温变形过程中发生了大范围的动态再结晶。

The atomization-twin rolls quenching technology was successfully utilized to prepare rapidly solidified Mg-6wt%Zn alloy in the form of flakes,and then rapidly solidification / powder metallurgy Mg-6Zn alloy in the form of rods were prepared by hot extrusion on the basis of the flakes.The microstructure,mechanical properties at room and elevated temperature were investigated.The results show that the microstructure of the rapidly solidified Mg-6Zn alloy is refined and the grain size is 1～2 μm.A large number of fine precipitates distribute in the alloy during the hot extrusion.Moreover,the high-density dislocations are observed in the rapidly solidification / powder metallurgy Mg-6Zn alloy,which is composed of α-Mg,Mg51Zn20 and a few Mg2Zn3 phases.All of these are beneficial to enhance mechanical property,and the compressive strength of the alloy is up to 300 MPa.However,the strength of the alloy greatly decreases with the increase of temperature.The main reason is that dynamic recrystallization occurs during the compressive deformation at higher temperature.