Understanding the Environmental Sensitivity of Nickel(3) Aluminum

Abstract

A Controlled Environment Transmission Electron Microscope was used to investigate the failure of a boron-free polycrystalline Ni3Al alloy produced by cold rolling and recrystallizing a single crystal in hydrogen. The effect of hydrogen is to lower the threshold stress for the nucleation of dislocations from grain boundaries and crack tips. The result will be decreased elongation due to the growth of cracks at lower stresses. X-Ray Diffraction and Orientation Imaging Microscopy were used to investigate the grain boundary type distribution. The misorientaion indicates strong texture consisting of the superposition of three texture components: 65% of grain boundary length results from +/-35° rotations, 25% from Sigma3 boundaries and 10% from low angle boundaries. The increased number of special boundaries will lead to the increased elongation and change in fracture mode.