Investigating the mechanisms that cause quench cracking in aluminium alloy 7010

Quenching large 7010 forgings from the solution heat-treatment temperature into cold water can result in cracking. Quench cracking occurs when the material is unable to accommodate the plastic strains that result from the differential thermal contraction during quenching. Chemical composition has been found to influence the propensity to quench crack with a high purity low iron and silicon version alloys demonstrating the greatest susceptibility. In order to understand the mechanisms behind the phenomenon, three different grades of wrought 7010, the chemical composition of which vary within the 7010 specification, were tensile tested around the solution heat-treatment temperature. Both plain and notched tensile tests were conducted. Qualitative optical microscopy methods in conjunction with scanning electron microscopy analysis were used to examine the microstructures and the fracture surfaces.