In Ni3Al alloys the yield stress increases with increasing temperature up to a maximum stress, reached at the temperature Tp. Below Tp glide occurred on primary octahedral planes whereas above Tp glided on primary cube planes was dominating. Therefore this change of glide planes was considered to determine Tp. Transmission electron microscopic investigations were carried out in order to study the mechanisms that control Tp in Ni3Al specimens with [001] compression axis. In this case no shear stresses were acting on any of the cube glide systems. The transmission electron microscopic results revealed a marked change in the dislocation structure on the {111} glide planes below and above the peak. The breakdown of the barriers (locked screw dipoles) began when the diffusion was high enough to facilitate their annihilation. The dynamic recovery of the locked screws occurred by multiple cross-slip via octahedral planes. It was proposed that, in this and other ordered alloys, the value of Tp was diffusion-controlled.

What Determines the Peak-Temperature in Binary Ni3Al? Rentenberger, C., Karnthaler, H.P.: Materials Research Society Symposium – Proceedings, 1995, 364[2], 689-94