Papers by Author: Heng Zhi Fu

Abstract: Microstructure of the arc-melted Cr-20at%Nb alloy solidified in different positions was investigated using optical microscope (OM) and scanning electron microscope (SEM). The results show that fully coupled eutectic was developed at the bottom of the ingot and then the eutectic experienced a columnar to equiaxed transition due to the decrease of G/V ratio (G the thermal gradient and V the solidification rate) with increasing the solidification distance. A novel lamellar structure was observed in the middle side of the arc-melted ingot, which may form by means of the eutectoid reaction of C14-Cr₂Nb→C15-Cr₂Nb+Crss. With the increase of the solidification distance from the middle side to the top side, the primary Cr₂Nb phase underwent a nonfaceted to faceted transition.

Abstract: This paper has systematically studied the evolving process of column crystals of Ti46Al0.5W0.5Si alloys that is directionally solidified by rectangular cold crucible. The results showed that: the solid/liquid interface presented convex to the liquid metal due to the complicated influences by cold crucible. Overheating temperature and new crystal nucleus had great effects on the growth continuity and the stability of column crystals. Furthermore, the precipitation phases have been studied. As a result, the methods for controlling growing process of columnar crystals have been submitted, which are playing a critical role in optimizing experimental parameters and devising the construction-elements of cold crucible.