Abstract
The cast microstructure of 1st generation MoSiBTiC alloy composed of Mo solid solution (Moss), Mo5SiB2, TiC phases largely affects tensile-creep behavior in the ultrahigh temperature region. Mo5SiB2 phase crystallized during solidification is plate-like with a size of several tens of microns. The plate surface is parallel to the (001) basal plane, and the <100] directions preferentially grow along the cooling direction, and thereby Mo5SiB2 has a strong texture while Moss and TiC show randomly-oriented distribution in a cast ingot. During creep, Mo5SiB2 plates are largely rotated and Moss works as sticky ligament in the small-plate-reinforced metal-matrix composites. This may be the reason why the MoSiBTiC alloy exhibits large creep elongation and excellent creep resistance. In other words, the evolution of microstructures infers that the consummation of Mo5SiB2 plate rotation may lead to the initiation of creep rapture process. Therefore, the unique microstructure formed during solidification provides the feature of good mechanical properties for the 1st generation MoSiBTiC alloy.