High-strength molten β-Titanium alloy


I. M. Frantsevich Institute for Problems of Materials Science of the NAS of Ukraine, Krzhizhanovsky str., 3, Kyiv, 03142, Ukraine
Modern Problems in Physical Materials Science - Kiev: Frantsevich Institute for Problems of Materials Science NASU, 2008, #17


β-Titanium alloy with bimodal structure – dendrites of solid solution with 1-10 um size and second-phase particles with 0,1-0,3 um size – is obtained with method of cooling of liquid solution (% (аt.)) of 34,9Ti-15,0Zr-30,1Co-5,0Ni-7,9Cu-5,0Ga-2,2Si to room temperature with cooling rate of 800-900 0С/s. X-ray and differential thermal analysis, scanning and transmission electron microscopy, low-temperature (Т = 20 0С) automatic indentation with Berkovich pyramid and high-temperature (Т = 20?1000 оС) short (1 min) and long (1-60 min) indentation with Vikkers pyramid, thermal activation analysis of temperature dependency of hardness are applied. Heat treatment regime influence on structural and phase state of the alloy and its mechanical properties are studied. Alloy resistance to external mechanical action Н/Е* and the hardness HIT under 20 оС in tempered condition and also after annealing in the temperature range of 400-1000 оС are shown to be significantly higher than those of macrocrystalline and cryptocrystalline, and are correspondent to those of nanocrystalline. Alloy is found to have high thermal stability: mechanical properties under 20 0С remain unchanged after annealing in thermal range of 400-1000 0С (t = 10-120 min). The alloy is almost not creeping and may be considered to be heat-resistant under Т?800 0С. The factors which determines high strength characteristics and thermal stability of given composition of the alloy in wide range of temperature and loading time are the following: high dispersion and uniformity of bimodal structure elements distribution, high distribution density of second-phase particles in matrix; increased stress in matrix, determined by high distribution density of the particles.