Flow stress and work hardening behaviour of Mg-3Al-1Zn alloy

Abstract

In the present study, the uniaxial tensile flow stress behaviour and work hardening behaviour of AZ31B alloy has been investigated across a wide range of temperature (25 °C–250 °C) at quasi-static strain rates (10⁻¹·s⁻¹–10⁻³·s⁻¹). The flow stress behaviour of the AZ31B sheet has been analysed at different temperatures, quasi-static strain rates and sheet orientations. It has been found that flow stress behaviour is highly influenced by the variation of temperatures, strain rates, and sheet orientations. The various important mechanical properties such as yield strength, ultimate tensile strength, percentage elongation, strain hardening exponent, and strain rate sensitivity have been determined. There has been a significant improvement in ductility (201.71%) of AZ31B alloy at 250 °C compared to 25 °C. The decrement in yield strength and ultimate strength has been found to be 47.52% and 53.66%, respectively. It has been observed that the AZ31B alloy is found to be more strain rate sensitive at elevated temperature (m = 0.11, at 250 °C) as compare to 25 °C. The various empirical hardening equations such as Hollomon, Ludwik, Ludwigson, Swift, and modified Voce have been formulated for a wide range of temperatures, strain rates, and sheet orientations. The K-M plots show three-stage of work-hardening behaviour for AZ31B alloy. Based on the performance comparison of different models, the Swift and Modified Voce efficiently predict the flow curve with correlation (more than 99%) at different temperature ranges. The fracture surface is analysed by FESEM. The quasi cleavage and river-like pattern are observed for the room temperature fractured specimen. The increase in temperature converts the mode of fracture from cleavage to ductile fracture.