On the optimization of temperature and cooling rate to maximize strength and ductility of near α titanium alloy IMI 834

Abstract

Microstructural features that vary in morphology, topology and size affect the static and dynamic mechanical properties of titanium alloys both individually and synergistically. These microstructural features are in turn influenced by the post deformation heat treatment parameters such as temperature and cooling rate. In the current study, near alpha titanium alloy IMI 834 was subjected to solution treatment followed by cooling in seven different media. Apart from conventional cooling media viz., water, oil, air and furnace, three other cooling medium were identified and used to bridge the large cooling rate gap that exists between air and conventional furnace cooling. The effect of solution treatment temperature and cooling rate on the microstructure and room temperature tensile properties of the alloy has been evaluated and reported here. An attempt has been made here to establish the correlation between the heat treatment parameters and all the resulting tensile properties such as yield strength, ultimate tensile strength, elongation, reduction in area (RA), strain hardening exponent (n), energy under the plastic region or toughness using response surface methodology (RSM) based on general factorial design (GFD). Based on the correlation, the optimum heat treatment parameter viz., temperature and cooling rate that maximizes both strength and ductility of the material has been identified using desirability function approach.