2A02铝合金过烧组织特征及金相检验技术的改进

为了更精确地评定铝合金过烧组织,以2A02变形铝合金为例,通过过热淬火处理制取金相试样,对传统的金相检验方法进行了技术改进,并对过烧组织特征及力学性能进行了分析。结果表明:使用体积分数为05.%的氢氟酸浸蚀试样有助于在光学显微镜下准确地判定临界过烧组织;扫描电镜和能谱分析可以帮助操作人员准确区分临界过烧状态组织的特征和相。2A02铝合金在510℃以下固溶的显微组织正常,硬度随固溶温度上升稍有增加;在510℃以上固溶时,会逐渐出现初熔小球,有轻微过烧现象;在520℃时出现断续网状复熔、晶界,为典型的过烧组织;在530℃时晶界复熔加粗,出现大尺寸复熔球,为严重过烧组织;在550℃时,局部复熔球变成空洞;铝合金在过烧后,其硬度和耐腐蚀性急剧下降。

Characteristics of 2A02 Aluminum Alloy Overburned Structure and Optimization of Metallographic Examination Technology

In order to evaluate the overburned structure of aluminum alloy more accurately in metallographic examination process,taking 2A02 wrought aluminum alloy as an example,metallographic samples were prepared by superheating quenching.The traditional metallographic examination method was improved,and the characteristics and mechanical properties of overburned structure were analyzed.The results show that the volume ratioof 05.%hydrofluoric acid etching is helpful to accurately determine the critical overburned structure under optical microscope.Scanning electron microscope and energy spectrum analysis can help operators to distinguish the characteristics and phase of critical overburned structure accurately.The microstructure of 2A02 aluminum alloy is normal when the solid solution temperature is below 510℃,and the hardness increases slightly with the increase of solid solution temperature.When the solid solution temperature is above 510℃,the primary melting ball gradually appears with slight overburned phenomenon.The intermittent network remelting grain boundary appears at 520℃,which is typical overburned structure.The grain boundary remelts and coarsens,and large-size remelting ball appears at 530℃,which is serious overburned structure.The local remelting ball becomes cavity at 550℃.The hardness and corrosion resistance of aluminum alloy decrease sharply after being overburned.