Validation of the quench factor technique in predicting hardness in heat treatable aluminum alloys

Abstract

This paper explores the relationship between the heat transfer mechanisms and metallurgical transformations associated with spray quenching in the heat treating of aluminum alloys. A method known as the quench factor technique is presented as a means for predicting the hardness and strength of aluminum alloys following a procedure of solution heat treatment with spray quenching and artificial age-hardening. It is shown that the only input parameter for predicting hardness of a particular alloy is its temperature-time history during quenching. Temperature-time quench data measured both in small specimens and a relatively large L-shaped specimen are combined with metallurgical transformation data for aluminum alloy 2024-T6 to predict Rockwell B hardness. The predicted hardness compares well with the values measured for both types of specimens. These results both demonstrate the validity of the quench factor technique and emphasize the need for tools which would facilitate accurate prediction of the temperature-time history during spray quenching. Such tools could ultimately enable the aluminum industry to produce parts with both large and uniform hardness and strength by careful manipulation of the sprays.