The synergistic strength-ductility mechanism of the in-situ constructed interfacial/intragranular hierarchical structure in nano particulate reinforced (TiB+La$_2$O$_3$)/Ti composites

Abstract

The strength-ductility trade-off has hindered the widespread application of powder metallurgy (PM) titanium matrix composites (TMCs). In-situ planting nano-particles as ultra-fine networks into the TMCs powder and constructing the interfacial/intragranular hierarchical microstructure have emerged as a promising strategy to overcome the strength-ductility trade-off. In the present work, we precisely controlled the distribution of the network nano-particles by adjusting the sintering temperatures and successfully transformed the ultrafine network into the interfacial/intragranular structure. The well-designed (TiB + La$_2$O$_3$)/IMI834 TMCs demonstrated exceptional mechanical properties, achieving a tensile strength of 1158 MPa while maintaining an elongation exceeding 8.6 %—performance comparable to wrought TMCs without requiring thermo-mechanical processing. The dislocation evolution and the slip activation behavior were investigated by in-situ synchrotron X-ray diffraction experiments and interrupted in-situ SEM-EBSD observations, which provided new insights into the strength-ductility synergy mechanism of the interfacial/intragranular nano-particles. These studies revealed that the hierarchical structure enhanced the dislocation storage capacity while simultaneously promoting slip activation. This dual effect facilitated multi-system sliding, which effectively optimized dislocation distribution and reduced stress concentration. This study visually elucidates the synergistic strength-ductility mechanism of the interfacial/intragranular hierarchical structure and establishes a straightforward and reliable approach for manufacturing high-performance PM TMCs