β - 안정화 원소가 첨가된 TiAl 합금의 특성 1. 고온 상변태

Abstract

The phase transformation of TiAl-X (X = Mo, W, Re) system at elevated temperatures was investigated by analyzing the dendritic morphologies of TiAl-X alloys and by constructing pseudo-binary phase diagrams of TiAl-2X ternary alloys. It was found that the addition of β stabilizers such as Mo, W, Re shifted the high temperature region of the binary Ti-Al phase diagram to the high Al composition side so that β phase forms as a primary crystal even at higher Al composition compared with the binary Ti-Al system. It also appeared that those β stabilizers shifted melting temperature and β phase region to low temperature and high Al composition side comparing the TiAl-2X (X = Mo, W, Re) pseudo binary phase diagram with the binary TiAl phase diagram. From the partial liquidus projections and pseudo-binary phase diagrams, the degree of `β stabilizing effect` was found to be in the following order : W$gt;Re≥Mo.