Effect of strontium on the microstructure, mechanical properties, and fracture behavior of AZ31 magnesium alloy
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- Zeng, X., Wang, Y., Ding, W. et al. Metall and Mat Trans A (2006) 37: 1333. doi:10.1007/s11661-006-1085-8
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The effect of strontium (Sr) on the microstructure, mechanical properties, and fracture behavior of AZ31 magnesium alloy and its sensitivity to cooling rate are investigated. Three phases—blocky-shaped Mg17Al12, acicular Mg20Al20Mn5Sr, and insular Mg16(Al,Zn)2Sr—are identified in the Sr-containing AZ31 alloys. With increasing cooling rate, the blocky-shaped Mg17Al12 phase increases, the acicular Mg20Al20Mn5Sr phase diminishes, and the insular Mg16(Al,Zn)2Sr phase is refined and granulated. The study suggests that the grain size decreases with increasing cooling rate for a given composition. However, the grain size decreases first, then increases, and finally decreases again with increasing Sr for a given cooling rate. The yield strength (σy) of AZ31 magnesium alloy can be improved by grain refinement and expressed as σy=35.88+279.13d−1/2 according to the Hall-Petch relationship. The elongation increases when Sr is added up to 0.01 pct and then decreases with increasing Sr addition. Grain refinement changes the fracture behavior from quasicleavage failure for the original AZ31 alloy to mixed features of quasicleavage and microvoid coalescence fracture.