A New Approach to the Requirements of Casting Factors in Investment Cast Aluminum Alloys

Abstract

A study was conducted with aluminum investment castings manufactured from A356-T6 and 357-T6 alloys, to develop a fundamentally derived quality model based on the flow stress (true-stress true-strain) behavior observed during tensile testing. The tensile elongation and tensile strength of alloys are particularly sensitive to the presence of casting defects and microstructural inhomogeneities that cause unstable plasticity, and, as a result, these properties together are useful measures of casting quality. Methodology involving procedures and models based on the Ludwik-Holloman relationship have been used to determine the requirements of aluminum able to be categorized as being defect free. The validity of the models has been experimentally proven.

Based on the methodology presented, it will be shown how this procedure may be used to develop both material and processes, and then to assign casting factors based on a physical meaning. The outcomes, derived from these quality parameters, may then be applied to cast alloys. The methodology presented may also be used by suppliers to prove the capability and statistical reproducibility of their product or processes. Examples will be provided as to how the methodology has been successfully applied to production aerospace components designed to be classified as Casting Factor 1.0.