Strengthening-toughening mechanism study of powder metallurgy Ti-Si alloy by interrupted in-situ tensile tests

Strengthening-toughening mechanism of powder metallurgy Ti-Si alloy was investigated by interrupted in-situ tensile tests. The fabricated Ti-Si alloy was strong and ductile. Slip band was blocked mainly by solutes and grain boundaries. Narrow deformed strips, aligned low angle grain boundaries and twin boundaries also played a positive role in this blockage. Cross-slip in the strain hardening stage lowered the difference value of ultimate tensile and yielding strength. Two-stage toughening mechanism was studied (necking onset was demarcation point). In the homogeneous deformation period before necking, strain compatibility was improved by the intergranular rotation (rotation axis along [0001], [-1100] and [-1102]), high-angle intragranular rotation, intergranular sliding and minor twinning deformation. In the heterogeneous deformation period after necking, microcracks initiation/coalescence was dragged by uniform stress distribution. Cracks propagation was also suppressed by dense grain boundaries and front plastic grains. The present comprehensive analysis of strength and toughness provided an in-depth understanding about the relationship among the processing, mechanical properties and microstructure of Ti alloy.