Microstructure, properties and cryogenic temperature deformation mechanism of a cryogenic titanium alloy with high-oxygen

Abstract:

In this study, the microstructure, properties and cryogenic temperature deformation behavior of cryogenic titanium alloy bars with different oxygen contents was investigated, and the strengthening-toughning mechanism of cryogenic titanium alloy with high oxygen content has been revealed. After annealled at 750℃, the microstructue is equaxied α_p phase with dispersed β phase. Due to the α/β phase trasformation temperature affected by the oxygen content, the microstructure of extral-low oxygen content alloy with 0.07wt.% is typical Widmanstatten microstructure with grain boundary α phase and lamellar α/β phase, and the media and high oxygen content is typical bimodal structure after annealled at 950℃. The ultimate tensile strength increase with increased oxygen content. The ultimate tensile strength of high oxygen content alloy at 20K is 1686.42MPa, and the corresponding elongation is 10.96%, while the ultimate tensile strength of high oxygen content alloy at 300K is 838MPa, and the corresponding elongation is 19.0%, which is better than the corresponding properties of TA34 alloy reported at GJB 9583. The deformation mechanism investigated finds that the discations strengthening of equaixed α_p phase and β phase bounadry caused by the non-crystallographic orientation relationship of α_p phase and β phase, which is the key factor of strength increase. As for the high oxygen content alloy with 0.16wt.%, the plasticity at 20K is obtained by the dislocations slip of prismatic and pyramidal , and the activation of stack facults and twins, which breakthrough the inhibition of twins deformation by high oxygen content, and the dislocation accumulated at boudaried and interacted in α phase can improve ultimate tensile strength.