EPM법에 의해 제조된 g-TiAl 합금의 열간 단조조건과 상변태 특성의 연관성

초록

An experimental was performed to establish the optimum hot forging conditions in γ TiAl based on the fractional ratio of phases formed under varying reaction rate, temperature and holding time during reaction. The chemical composition of the experimental alloy was Ti-46.6Al-1.4Mn-2Mo(at%) and elemental powders were used as raw materials to synthesize the alloy. Representation phases in reaction-sintered elemental powders consisted of TiAl, Ti3Al and TiAl3, and a fast heating rate increased the amount of Ti3Al but decreased that of TiAl3. The minimum heating rate required to suppress the TiAl3 phase was 5℃/min. A sound γ-TiAl with fully lamellar microstructure of 50㎛ in size was obtained by soaking and forging at 1000℃, followed by a heat treatment. A similar result was obtained by high frequency induction heating with 300℃/min heating rate. Heat treatments to obtain fully lamellar microstructure regenerated pores, the reason being retention and transformation of TiAl3 phase which was confirmed by EPMA and EDS analysis.