In-Situ Observation of Crack Propagation and Microstructure Characterization in Ti/Al3ti Metal-Intermetallic Laminate (Mil) Composites

Abstract

Ti/Al3Ti Metal-Intermetallic Laminate (MIL) composites are fabricated by the endothermic semi-solid technique. The microstructure of tested specimens and the micrograph metallography were examined by SEM, and the Orientation image microscopy (OIM) and phase composition were characterized by EBSD technique. Meanwhile, the characterization of local strain and the fracture behavior of Ti/Al3Ti MIL composites was conducted by DIC and in-situ tensile experiments, respectively. Results show that Ti/Al3Ti Metal-Intermetallic Laminate (MIL) composites with free-of salient defects, Kirkendall voids and centerlines, are fabricated by adjusting hot pressing parameters in the endothermic semi-solid reaction technique. The texture of (100) <001> and (110) <001> are specified in Al3Ti layer, and that of (100) <001> in TC4 layer is determined by EBSD characterization. Additionally, delamination is locally developed in Ti/Al3Ti interfaces, and the overall fracture in the middle of specimens is specified in the tensile testing. The fracture resistance of Al3Ti layer is significantly improved by the plastic deformation of TC4 and the suppression effect on the crack tip. It is found that the extrinsic toughening mechanism contains crack deflection, crack blunting, crack bridging, multiple cracking mode, and the plastic deformation of ductile TC4 layers in Ti/Al3Ti MIL composites. The real-time observation technique perhaps provides more complete insights into the relationship between fracture behaviors and enhanced toughness.

Keywords: MIL composites, In-situ tensile, Texture, Crack propagation, Toughening mechanism