Effect of TiB2 particulate on partial remelting behavior of Mg–11Al–0.5Zn matrix composite

Abstract

Abstract Partial remelting behaviors of Mg–11Al–0.5Zn alloy and TiB 2 /Mg–11Al–0.5Zn composite are investigated by the isothermal holding at the temperatures of 510 and 545 °C. The result shows that, although, the TiB 2 addition has no influence on the remelting characteristics of eutectic and liquidus temperatures of the composite, it has a great effect on the remaining liquid located at the grain boundary. With a processing temperature of 545 °C, the remaining liquid is dramatically decreased in the composite, compared with that in the unreinforced matrix alloy. Furthermore, the solid α-Mg grain size in the composite does not significantly reduce compared with that in the matrix alloy; however, the microhardness of the α-Mg grain is increased in the partial remelting microstructure in the composite. Although most of the TiB 2 particulates are present in the remaining liquid phases distributed at the grain boundaries, some liquid islands are entrapped inside α-Mg grains. As a consequence, the TiB 2 particulates can eventually reside within the grains after complete solidification. However, it is difficult that TiB 2 particulate is directly incorporated (engulfed) into the Mg–11Al–0.5Zn matrix alloy during the regular solidification process. Furthermore, the DTA, SEM and XRD results reveal that no reaction occurs between the TiB 2 particulate and matrix alloy during the partial remelting process, which indicates that TiB 2 particulate is thermodynamically stable at the Mg–11Al–0.5Zn matrix alloy.