In situ high-energy X-ray diffraction studies of deformation-induced phase transformation in Ti-based amorphous alloy composites containing ductile dendrites

The deformed-induced microstructure evolution and phase transformation behavior of Ti-based amorphous alloy composites (AACs) containing ductile dendrites in situ formed during solidification were investigated using ex situ transmission electron microscopy (TEM) and in situ high-energy X-ray diffraction (HE-XRD). In situ synchrotron-based HEARD experiments provide clear evidence on the deformation-induced phase transformation from beta to alpha '' martensite initiated already in the linear elastic stage of the macroscopic stress strain curve. Detailed analyses from the diffraction experiments show that the grains that were aligned with [0 0 1]beta along the loading direction (LD) were then easily transformed into alpha '' martensite, whereas the martensitic variants oriented with [1 0 0](alpha)(n), along LD were preferentially formed under compression. The current study provides quantitative information about changes in various microstresses between the crystal phase and the amorphous matrix during deformation. Enhancement of the macroscopic plasticity of the AACs was mainly attributed to the strain relaxation in the beta phase and to the formation of multiple shear bands in the amorphous matrix triggered by the deformation-induced phase transformation inside beta, knowledge of which greatly deepens understanding of the complex micromechanical behaviors in advanced AACs. (C) 2013 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.