Effect of nano-particles on the creep resistance of Mg–Sn based alloys

A study has been made on the microstructure and high-temperature properties of die-cast Mg–Sn–Al–Si (TAS831) alloy. Microstructure of TAS831 alloy is characterized by the presence of thermally stable Mg2Sn nano-particles within the matrix. It also contains Mg2Sn and Mg2Si particles along grain boundaries. It has been shown that the morphology of matrix Mg2Sn particles varies depending on cooling rate, forming rod-type Mg2Sn particles at fast cooling rates and polygonal particles at slow cooling rates. Elevated-temperature creep tests show that the die-cast TAS831 alloy has superior creep resistance compared with commercial AZ91 alloy. Analyses of creep and load relaxation at elevated temperatures in the context of internal-variable theory indicate that the presence of thermally stable nano-particles within the matrix increases the resistance to dislocation movement, thereby improving the creep resistance.