Effect of temperature on the mechanical behaviour of magnesium alloy AZ91D in the range between −30 °C and 250 °C

• The temperature effect on the mechanical behaviour of magnesium alloy AZ91D is studied.
• As the temperature increases, both yield and peak stresses decrease and fracture strain increases.
• Hardening behaviour at dynamic rates is maintained for a long strain range even at elevated temperature.
• Alloy deforms by slip and twining at lower temperature while dominantly by slip at elevated temperature.
• Micro-cracks at the interface of β-phase and α-matrix cause detrimental effects on the mechanical properties.

The temperature effect on the behaviour of magnesium alloy AZ91D is investigated. The temperature is varied between −30 °C to 250 °C. It is observed that the effect of temperature on the mechanical behaviour of the alloy under tension is dissimilar to compression. Under tensile loading, the effect of temperature is little at quasi-static strain rate while significant at 1500 s−1. On the other hand the effect of temperature is considerable at quasi-static strain rate while little at 2500 s−1. Thermal softening, voids and cracks in β-phase and favourable orientation of crystals in the direction of tensile loading are responsible for reduced tensile stress at 1500 s−1 strain rate and 250 °C temperature. Microstructure analysis reveals that at elevated temperature additional slip systems are activated causing the stress of the alloy to decrease and ductility to increase. Furthermore, the hard and brittle intermetallic β-Mg17Al12 decomposes into aluminium and magnesium giving rise to the nucleation of micro-cracks at the interface between β-phase and the magnesium-matrix causing detrimental effect on the mechanical properties of the alloy.

The effect of temperature is investigated for magnesium alloy AZ91D. Under tensile loading, the effect of temperature is little at quasi-static strain rate whereas considerable on dynamic strain rate. Under high strain rate compression at elevated temperature, the hardening behaviour of the alloy due to dynamic strain rate is maintained for a long strain range which is not observed at quasi-static strain rate due to thermal softening. Good strength, fair amount of ductility and good energy absorption even at elevated temperatures makes this alloy a potential candidate for structural applications in automotive, aerospace and other such applications.Figure optionsDownload as PowerPoint slide