Strengthening and deformation mechanism of selective laser-melted high-concentration nitrogen solute α-Ti materials with heterogeneous microstructures via heat treatment

Light elements such as oxygen (O) and nitrogen (N) significantly impact the microstructure and mechanical properties of Ti-based materials through solid solution strengthening. The microstructures of Ti-based materials processed via selective laser melting (SLM) have also been observed to contain a martensitic phase that improves the tensile strength. However, this improvement is achieved at the cost of reduced ductility. This study considered the use of post-heat treatment N dissolution to enhance the ductility of SLM-processed alpha-Ti materials. Tensile testing of the as-fabricated SLM Ti-(N) revealed a significantly increased strength of similar to 1200 MPa and a low ductility of 5% for N content of 0.5 wt%. However, the quenched samples exhibited increased ductility by up to 20%, with the microstructure, including primary alpha(alpha(p)) and transformed beta structures. Further examination via electron probe micro-analysis (EPMA), transmission electron microscopy (TEM), in-situ high-temperature SEM observation and in-situ EBSD observation during tensile testing revealed that the enhancement in ductility of the quenched SLM-processed Ti-(N) samples was significantly due to alteration of the grain morphology, dislocations and N distribution. The findings of this study further clarify the microstructural evolution and deformation response of SLM-processed Ti-(N) materials under water quenching.

Automated summary

This study investigates the enhancement of ductility in SLM-processed Ti-(N) materials through post-heat treatment N dissolution, finding that quenching significantly increases ductility by altering grain morphology, dislocations, and N distribution. Examination techniques such as EPMA, TEM, high-temperature SEM observation, and in-situ EBSD observation during tensile testing were utilized to clarify the microstructural evolution and deformation response of the materials.