Microstructure and elevated temperature properties of die-cast AZ91-xNd magnesium alloys

The effect of Nd addition on the microstructure and mechanical properties of a die-cast AZ91 alloy was investigated in the present work. The results show that the die-cast AZ91 alloy is composed of α-Mg matrix and γ-Mg ₁₇Al ₁₂ phase. Nd addition into the AZ91 alloy leads to the formation of rare earth containing intermetallic phase. Al ₄Nd phase forms when Nd content is less than or equal to 1.0 wt.%. Al ₂Nd phase appears simultaneously when Nd content reaches to 3.0 wt.%. The size and volume fraction of γ-Mg ₁₇Al ₁₂ phase decrease, because of the newly formed Al-Nd phase. And the γ-Mg ₁₇Al ₁₂ phase distributes from reticular to dispersive. Nd addition has a little effect on the room temperature properties of the die-cast AZ91 alloy, but greatly improves the elevated temperature properties. The tensile strength of AZ91-0.5Nd and AZ91-1.0Nd alloy tested at 150 °C is even close to the room temperature strength. The AZ91-1.0Nd alloy has the optimal properties.