摘要
通过静载荷试验研究了触变成形AZ91D镁合金在NaCl溶液中的应力腐蚀行为。结果表明,随着载荷和NaCl浓度的增大,试样的断裂时间逐渐缩短,而当增大溶液的pH值时,断裂时间却相对延长。通过扫描电镜对断口的分析表明,在酸性NaCl溶液中,合金呈现出明显的沿晶断裂方式,在紧靠裂纹的前缘处,会形成类似于韧窝的空穴,断口由许多曲曲折折的小平面组成;而在碱性NaCl溶液中,由于断裂所需的时间长,使得试样断口有较大的塑性变形,断口边缘有许多撕裂的片状痕迹。触变成形AZ91D镁合金应力腐蚀过程主要分为钝化膜的破裂、点蚀、裂纹的萌生、裂纹扩展和断裂4个阶段。
The stress corrosion behavior of thixoformed AZ91D Mg alloy in NaCl solution was investigated by means of constant load test. The results indicated that the fracture time decreased with the increase of load and concentration of solution , while it increased with the increase of pH value of solution. By analyzing with SEM, it could be concluded that in acidic NaCl solution, the fracture path of thixoformed AZ91D alloy propagated along grain boundary, the crack front fracture surface presented some cavities similarly dimple, and fracture surface consisted of small flections planes. However in alkaline NaCl solution, the fracture facet showed obvious plastic deformation because of prolonged time to fracture, and there were a large number of sheets trace at the fracture edge, which was different from the samples of metal mould. It was because that the thixoformed AZ91D Mg alloys have superior characteristic of SCC. The stress corrosion was divided into four steps; the passive film destroy, pitting corrosion, cracking generation and crack extend and fracture.
出处
《材料保护》
CAS
CSCD
北大核心
2007年第10期12-15,44,共5页
Materials Protection
基金
863计划国际合作项目(2002AADF3303)
第三批中-以合作基金项目(2002-02)
关键词
触变成形
镁合金
应力腐蚀
脆性断裂
断口形貌
thixoformed
magnesium alloys
stress corrosion
brittle fracture
fracture morphology
