Minimization of residual stress in heat-treated Al-Si-Mg cast alloys using uphill quenching: Mechanisms and effects on static and dynamic properties

A method to minimize residual stresses in heat-treated Al-Si-Mg cast components is presented. Compact tension specimens, commonly used for fatigue crack growth testing, were machined from sand castings and tested after T61 heat treatment. The specimens prepared using a conventional T61 treatment had significant residual stresses, which severely affected their fatigue crack growth behavior. To reduce these residual stresses, a modified quenching methodology was used. The method consists of a conventional quench followed by an uphill quench, designed to counteract the residual stress effects introduced during the original quench. This article explains the mechanisms of residual stress formation, residual stress effects on fatigue crack growth, and methods to evaluate and control residual stresses. It also elaborates on the benefits of uphill quenching method, its underlying rationale, working principles, and processing parameters. The effects of the uphill quench on static and dynamic properties are also presented and discussed. (C) 2010 Elsevier B.V. All rights reserved.