상용 순수 티타늄의 심한 소성가공에 따른 미세조직 발현과 기계적 특성 변화 - 초기 입도 영향

Abstract

Commercial purity titanium of a hexagonal close packed a phase was plastic- deformed through equal channel angular pressing (ECAP). ECAP was conducted on specimens of different initial microstructure so that the effect of the initial grain size and texture on the subsequent evolution characteristics could be studied. Specimens of equiaxed microstructure were prepared with the initial grain size ranging from 4 μm to 60 μm. During deformation, low angle boundaries as well as twin boundaries were produced. Formation of twin boundaries was promoted by the large initial grain size whereas small angle boundaries were more readily generated in the initially smaller grains due to the difficulty of twinning. Through the tensile test, it was confirmed that the low angle boundaries and twin boundaries both increased the yield strength. Particularly, specimens of large grain size showed pronounced increment of the yield strength although the elongation was reduced due to the twin boundaries produced during the deformation.