Significantly improved strength of the TiC/TA19 composites via interface and dislocation strengthening

Abstract

For titanium matrix composites (TMCs) with a dual-phase structure, yield strength (YS) is typically governed by the hard α phase rather than the soft β phase in the matrix alloy. Therefore, by controlling the precipitation of nanoscale secondary α phases (αs) within the β phase, lattice distortion can be induced, leading to dislocation pile-ups at the αs/β phase interface, thereby achieving strengthening of the matrix interface. Herein, TiC/TA19 composites were fabricated using spark plasma sintering, and induced the dispersion and pinning of nanoscale αs phases from the β phase at the αs/β phase interface through multi-pass cumulative rolling, achieving super high strength. In particular, the nanoscale αs phase exhibits two typical Burgers orientation relationships with the β phase, i.e. (0001)αs//(110)β & [11 2− 0]αs//[1− 11]β and (0001)αs//(01 1−)β & [11 2− 0]αs//[1− 11]β, respectively. Compared with the yield strength of sintered composites, when the rolling reduction was 75 %, the YS of TiC/TA19 composites increased by 33.7 %, reaching 1368 MPa, and the elongation was 3.6 %, only 0.7 % lower than that of sintered composites (4.3 %). The enhanced strength is mainly attributed to the αs precipitation for αs/β interface strengthening and dislocation strengthening derived from the TiC and nanoscale αs precipitates. The volume fraction of dynamic recrystallization grains in TiC/TA19 composites increased with the rolling reduction, and more pyramidal <c+a> slip systems were activated to coordinate the plastic deformation of the composites. This study offers a promising route to fabricating superior high-strength TMCs and provides new insights into balancing strength and ductility.