β - 안정화 원소가 첨가된 TiAl 합금의 특성 2. 일방향응고 및 기계적 성질

Abstract

The lamellar orientation of TiAl/Ti₃Al two phase alloy containing W was controlled to align at 0° and 45° to the growth direction by directional solidification (DS). The composition of β solidification in Ti-Al-W ternary system could be determined from the partial liquidus projection which was constructed by observing the microstructure of arc-melted buttons. The Ti-47Al-2W composition was selected for β solidification and the directional solidification was performed by using a Bridgman-type DS apparatus at the growth rate of 90 ㎜/hr. At the beginning part of the as-grown DS ingot, the columnar grains with the lamellar orientation at an angle of 0° (A orientation) and 45° (B orientation) to the growth direction were both observed, but the grains with A orientation disappeared increasingly. Finally, the columnar grains with B orientation coalesced to whole DS ingot. In the results of room temperature tensile test, Ti-47Al-2W DS alloy exhibited superior tensile elongation to the polycrystalline alloy having the same composition.