Abstract
The hardness of various Ti-base alloys was measured in high vacuum at temperatures up to 700° for the purpose of finding useful heat-resistant alloys. The results of the measurement are summarized as follows: (1) The hot hardness of annealed alloys increases with increasing Al contents. (2) The hardness of some alloys water-quenched from 900° is shown to be very high. This extraordinary hardness is ascertained to be due to tempering at 500°. Such alloys contain at least 6 pct. Al and 4 pct. Cr (or Cr+Mo). (3) The X-ray diffraction photographs for those temper-hardened alloys show that the β-phase retained in water quenching becomes rich in the content of Cr and Mo by tempering, while they give no evidence of the presence of the ω-phase. Thus it is supposed that the hardening is due to the precipitation of fine α particles from the original β solid solution.
