2A12方板裂纹原因分析

The analysis of the cracks on 2A12 square plate

牌号为2A12的铝合金方板在冷变形过程中发现表面和侧面有多处裂纹,经化学成分分析、宏观组织、断口、显微组织以及扫描断口能谱分析,结果表明:失效方板的化学成分符合GB/T3190-2008的要求,低倍组织除裂纹外没有发现其它缺陷,断口表面未发现氧化层,显微组织未过烧。失效方板开裂是淬火冷却过程中,内外温度差大,材料表面因急剧冷却收缩形成极大拉伸应力,当拉应力超过材料抗拉强度材料塑性变形极限时形成开裂,裂纹属于淬火裂纹。

Cracks on surface of aluminum square plate 2A12 are indicated in the process of cold work, then the necessary tests such as chemical composition, macro structure, micro structure, fracture analysis and SEM have been done, it is shown that chemical composition conforms to GB/T3190-2008, there is no other defects apart from cracks, no oxidation layer on the fracture surface and the plate was not overheated. Cracks are caused by the temperature difference between the inside and surface during the quench cooling, in which the strong tensile stress is caused because of the cooling shrink on the surface, cracks come when it exceeds the tensile strength. Thus, the cracks are quenching cracks.