Crystallographic study of Ni2Ge phase in binary Ni-Ge alloy system

The existence of Ni2Ge phase in a binary Ni-37.8 wt% Ge alloy has been determined by means of metallography, scanning electron microscopy, transmission electron microscopy and energy dispersive X-ray analysis. The crystal structure of the phase is found to be primitive orthorhombic with lattice parameters of a = 0.51 nm, b = 0.383 nm and c = 0.726 nm. Its space group has been determined to be Pnma (No. 62), by the reflection condition analysis of selected-area diffraction patterns and zone-axis symmetry analysis of convergent-beam electron diffraction patterns. Twinning has been observed to occur in Ni2Ge phase. Its shear plane, twinning plane and twinning direction have been determined to be (100), (011) and [0-11], respectively, by the analysis of transformation matrix and lattice structure of the twins. Copyright (C) 1996 Acta Metallurgica Inc.