The Evaluation of Mechanical properties on the Changes of Microstructure for Titanium Alloy (Ti-6Al-4V)

티타늄 합금(Ti-6Al-4V)의 조직변화에 따른 기계적 특성 평가

The characteristics of mechanical behavior were estimated for Ti-6Al-4V alloy with four kinds of microstructure prepared with heat treatments. For this study, impact test, tensile test and fatigue crack growth test were performed, and then compared mechanical properties on the four microstructures. Furthermore, for quantitative evaluation, fractal dimensions of crack pass were obtained using the box counting method. The main results obtained are summarized as follows. (1) The microstructures exhibited equiaxed microstructure, bimodal-microstructure and lamellar microstructure by heat treatment. (2) The impact absorbed energy and elongation is superior in the bimodal-microstructure, and the hardness and tensile strength are superior in the lamellar microstructure. (3) The fatigue crack growth rate is similar to all microstructures in the low ${\Delta}K$ region. The fatigue crack growth rate of equiaxed microstructure is fastest, and that of lamellar microstructure is lowest in the high ${\Delta}K$ region. (4) The fractal dimension D of lamellar microstructure is higher then that of the equiaxed microstructure and bimodal microstructure.