Effect of hot-pressing temperature on microstructure and the improvement of residual Al on tensile ductility of Ti/Al3Ti heterogeneous structure

Abstract

Ti/Al3Ti Heterogeneous Structures (HS) with different fractions of residual Al were fabricated at hot-pressing temperatures from 580 °C to 650 °C. The grain boundary distribution and Kernel Average Misorientation (KAM) were characterized by EBSD technique. The varied tensile properties and failure modes were specified, and the local strain evolution was analyzed by DIC. Results show that the distribution of grain boundary, the thickness of individual layers, and mechanical properties were significantly affected by hot-pressing temperature. The elongation of Ti/Al3Ti/Al HS was 64.2%–228.5% higher than that of Ti/Al3Ti HS, which was attributed to stabilized plastic flow and the regulating effect of residual Al. The improvement mechanisms of residual Al on tensile plasticity were found that normal strain was delocalized by promoting strain flow, and shear strain was stabilized by hindering effects. In addition, the tensile strength and work-hardening capability were enhanced by the grain refinement of TC4 layer. The failure mechanism, from HS650 to HS600, is found to transform from brittle fracture determined by normal strain into ductile shearing fracture governed by normal strain and shearing strain. The fracture micromorphology revealed that a mixed model of transgranular and intergranular was presented in the Al3Ti layers. Dimples were distributed in TC4 layers, and tearing ridges were overspread in Al layers. The current views on localized characterizations perhaps provide more complete insights toward the technics-properties design of Ti/Al3Ti HS.