Effect of Cryogenic and Electropulsing Coupling Treatment on Microstructure and Mechanical Properties of Ti6al4v Alloy

Abstract

In this study, the effects of cryogenic and electropulsing coupling treatment (CET) at -196°C for different time (8h, 16h and 24h) on the microstructure and mechanical properties of Ti6Al4V alloy in the rolled state were systematically investigated. The results indicate that after 16 hours of cryogenic and electropulsing coupling treatment, the microstructure inside the alloy is influenced by both the electron wind and the cold-shrinkage internal stress, resulting in a reduction in dislocation density within the alloy. Under the effect of electron wind force, the internal colony of the alloy shows vertical arrangement with obvious direction. The cryogenic field and pulsed electric field promote the internal generation of nanoscale precipitate phases in the initial α phase, leading to the entanglement of dislocations. The grain size of the alloy becomes smaller. The cryogenic environment can effectively avoid the thermal effect in the electropulsing, preventing the grain from coarsening, and the value of the thermal effect is greatly attenuated, generating small-sized grains after recrystallization. The combined effect of the electron wind force and the cold-shrinkage internal stresses cause the texture to undergo a selective orientation, and the (102) grain surface were deflected toward the (002) and (101) grain surfaces. The tensile strength of the cryogenic and electropulsing coupled 16h sample was 830.3 MPa, and the elongation was 11.23%, which were 5.8% and 16.7% higher than that of the untreated sample, respectively, and the dimples showed a large and deep state, which achieved the effect of simultaneous enhancement of strength and toughness.

Keywords: cryogenic and electropulsing coupling treatment, Ti6Al4V alloy, electron wind, cold-shrinkage internal stresses, strength and toughness