TiAl金属間化合物の高温変形

抄録

In order to study a posibility of hot working of TiAl, tensile and compressive tests of arc melted Ti-37 mass%Al have been conducted at high temperatures up to 1473 K and various strain rates.
On tensile testing, this material shows ductile behaviour above 1200 K and brittle fracture below this temperature. The critical brittle fracture stress was found to be constant and was about 320 MPa. Elongation increases remarkably above 1300 K.
The flow stress of this material at low strain rates coincides well with the hyperbolic relations proposed by Sellars et al. The flow stress at high srain rates estimated from this relation exceeds the brittle fracture stress, which means that a usual working process will not be applicable. For the successful hot working of this material, high hydrostatic compressive stress components have to be applied or the temperature and strain rate have to be adjusted so that the flow stress may become less than 320 MPa.
Fine recrystallized grains of average size 18 μm in diameter were obtained for the material strained to a true strain of 1.6 at 1300 K.