Semisolid microstructure evolution of AZ91D magnesium alloy refined by Al-Ti-B

Abstract

The microstructural evolution and corresponding phase transformations have been investigated during partial remelting of AZ91D magnesium alloy refined by Al-Ti-B master alloy. The effect of heating temperature on semisolid microstructure has also been discussed. The results indicate that the microstructural evolution process includes four stages, the initial rapid coarsening, structure separation, spheroidization accompanied by coarsening and the final coarsening. Two or more equiaxed dendrites in the as-cast microstructure evolve into one spheroidal primary particle in the semisolid microstructure through the former three stages. The initial rapid coarsening results from the reaction of b→a, the structure separation is due to the a + b→L and a→L, the spheroidization is attributed to the a→L and the final coarsening is ascribed to the two reverse reactions of a→L and L→a. Rising the heating temperature during partial remelting is beneficial for obtaining small and spheroidal primary particles.

Effects of Reheating Duration on the Microstructures and Tensile Properties of Thixoforged In Situ Mg2Sip/AM60B Composites

“…Unfortunately, most of the existing investigations have emphasized on the microstructural evolution during partial remelting of matrix alloys [16][17][18][19][20][21]. Only a few literatures have involved the microstructures and mechanical properties of the ''thixoforged'' alloys [22][23][24].…”

Heterogeneous Nucleation of Pure Magnesium on Al3Ti, TiC, TiB2, and AlB2 Particles

“…Recently, it has been reported that Al-Ti-B, and Al-Ti-C refiners can also be used for Mg alloys. [17][18][19][20][21] For example, the effect of a new Al-4% Ti-5% B refiner on the grain refinement of an AZ31 magnesium alloy has been investigated by Wang et al 18) However, the effect of Al-Ti-X refiners on the grain refinement of Mg and Mg alloys is still unclear. In this study, Al-5 mass % Ti, Al-3 mass % Ti-0.15 mass % C, Al-5 mass % Ti-0.2 mass % B, and Al-5 mass % Ti-1 mass % B are used as the master alloys, and the effect of these master alloys on grain refining performance of a pure Mg cast has been reported.…”