摘要
以Mg-12Zn-4Al-0.3Mn(质量分数,%)为母合金,制备了6种合金.实验观察证实,Mg-12Zn-4Al-0.3Mn合金的铸态组织由α-Mg基体和沿晶界分布的准晶Q相组成.在母合金中加入少量的Sr后,亚稳准晶相转变为Mg_(32)(Al,Zn)_(49)平衡相以及Mg_(51)Zn_(20)共晶相.在母合金中复合加入Sr与Ca后,铸态组织出现了Al_2Mg_5Zn_2共晶相.随着Sr含量的增加,合金室温和高温下的力学拉伸强度提高,高温蠕变性能下降;Sr与Ca的复合加入使合金抗拉强度和塑性下降,但高温屈服强度提高.在175℃/70 MPa条件下,Mg-12Zn-4Al-0.2Sr-0.4Ca-0.3Mn合金表现出良好的高温抗蠕变性能.
Magnesium alloys have emerged as potentially good candidates for numerous applica- tions, especially in automotive industry. Although the commonly used magnesium alloys, such as AZ91 and AM60 based on Mg-Al system have excellent castability, good room temperature mechanical properties and low cost, the application of these alloys has been limited to temperatures below 120 ℃ because of their poor heat resistance, especially creep property at elevated temperatures. Recent development reported that magnesium alloys with high zinc and low aluminum concentrations （Mg-Zn-Al based alloys） exhibit better creep properties than Mg-Al based alloys at temperatures above 150℃ and small amounts of alkaline-earth element （Sr and Ca） additions to the Mg-Zn-Al ternary alloys lead to further improvement of their mechanical properties. The purpose of the present paper is to describe the effects of calcium and strontium additions on the microstructure and mechanical properties of Mg-12Zn-4Al-0.3Mn based alloy. The results indicate that the as-cast microstructure of Mg-12Zn-4Al-0.3Mn alloy consists of the α-Mg matrix and a quasicrystalline Q phase at grain boundaries. Small amounts of Sr addition to the master alloy result in the transition of metastable Q phase to the equilibrium Mg32（Al, Zn）49 phase and the formation of binary eutectic phase Mg51Zn20. Another lamellar eutectic phase Al2Mg5Zn2 is observed in the as-cast microstructure when Ca combined with Sr is added to the base alloy, and its volume fraction increases with increase of Ca addition. The single addition of Sr causes the increase of tensile strength, but decrease of creep resistance at elevated temperatures. However, the creep properties are significantly improved if Sr is added in combination with Ca to the master alloy due to the formation of ternary eutectic phase Al2Mg5Zn2, which shows the high thermal stability at elevated temperatures. The alloy with composition of Mg-12Zn-4Al-0.2Sr-0.4Ca-0.3Mn exibits good creep resistance at 175 ℃ and 70 MPa
出处
《金属学报》
SCIE
EI
CAS
CSCD
北大核心
2009年第5期585-591,共7页
Acta Metallurgica Sinica
基金
国家科技支撑计划项目2006BAE04B07
江苏省重大科技成果转化专项资金项目BA2005004资助~~
关键词
镁合金
显微组织
力学性能
抗蠕变性能
magnesium alloy, microstructure, mechanical properties, creep resistance
