Effect of multi-stage heat treatment on mechanical properties and microstructure transformation of Ti-48Al-2Cr-2Nb alloy

Refining the grain size of gamma-TiAl alloys to improve their strength and ductility is of academic interest. Thus, we report a multi-stage heat treatment method consisting of solution treatment, cyclic heat treatment, annealing, short heat treatment, and aging to refine the microstructure of the Ti-48Al-2Cr-2Nb alloy. The solution-treated microstructure was refined from 1100 to 191 mu m by cyclic heat treatment, promoting feathery gamma packets. Fine duplex grains below 23 mu m were obtained through discontinuous coarsening, which was accelerated in the cyclic-heat-treated alloys owing to the high driving force resulting from the presence of feathery gamma packets and fine interlamellar spacing. Through the short heat treatment and aging at single alpha and alpha 2 + gamma fields, a tailored duplex structure with a grain size of 24 mu m and interlamellar spacing of 42 nm was achieved. Through microstructure refinement, tensile strength and elongation were improved to 697 MPa and 2.1%, respectively, compared to those of the conventional forged specimen (622 MPa and 1.3%, respectively). We believe that our study provides a simple pathway to refine the grain size and interlamellar spacing of gamma-TiAl alloys.

Automated summary

The study introduced a multi-stage heat treatment method to refine the microstructure of Ti-48Al-2Cr-2Nb alloy, achieving a tailored duplex structure with improved tensile strength and elongation. This study provides a simple pathway to refine the grain size and interlamellar spacing of gamma-TiAl alloys.