Analysis and Prevention of Cracks in 7055 Aluminum Alloy Parts

The cause for cracks in 7055 aluminum alloy parts during heat treatment process was analyzed, and prevention measures for the cracks were discussed and summarized based on the analysis results. The macro morphology of cracks, fracture morphology, metallurgical structure and micro-hardness of 7055 aluminum alloy parts manufactured by spray forming were analyzed by means of stereoscopic microscopy, optical microscopy, scanning electron microscopy(SEM), energy dispersive spectroscopy (EDS) and micro-hardness testing. The analysis results indicate that the composition, microstructure and micro-hardness show no abnormal evidence. The crack fracture is intergranular while the man-made fracture is mostly covered with dimples. Considering the preparation process of the material, it is supposed that the cracks in 7055 alloy parts are quenching cracks, which is related to the quenching sensitivity of the alloy and the heat treatment process. Measures were put forward to prevent quenching cracks, such as thorough homogenizing before quenching, lowering the quenching rate, controlling the shape of the part section and rounding for stress concentration regions.