Uphill Quenching of Aluminum Alloys—A Progress Report

Abstract

Abstract This paper describes the uphill quenching process which is applied in the heat treatment of aluminum alloys. This lesser known process was developed by Alcoa and first applied more than 50 years ago for aluminum alloys of several thicknesses. Uphill quenching has been reported to reduce residual stresses by > 80%. Typically, uphill quenching is applied after quenching and before aging of aluminum alloys. Uphill quenching consists of the immersion of the part in a cryogenic environment and after equilibration, the part is transferred immediately to a fixture in a superheated steam chamber to obtain a temperature gradient sufficient to maintain the improved mechanical properties gained with heat treatment that result in low residual stresses and superior dimensional stability. Assuming that most of the stresses that appear in aluminum alloys during heat treatment are due to the quenching process, then this intermediate treatment becomes a potentially effective tool for the heat treatment of aluminum alloys. The aim of this paper is to present an overview of recent work showing tensile test results obtained with uphill quenching relative to conventional quenching processes.