Investigation of tensile deformation behavior of a TWIP/TRIP metastable β titanium alloy at typical temperature part II: 20 K

The tensile behavior and deformation mechanism of Ti-10Mo alloy at liquid hydrogen temperature (20 K) were investigated. The results showed that Ti-10Mo alloy has a high UTS of 1553 MPa and a high YS of 1497 MPa at 20 K, as well as an excellent elongation after fracture of 11 %. This is due to the simultaneous activation of {332}<113> twin twins and SIM alpha" transformation during deformation, that is, the combination of TWIP and TRIP effects. The activation sequence of different deformation mechanisms is as follows: the primary SIM alpha" and {332}<113> twins are first activated simultaneously. With the increase of strain, multiple variants of SIM alpha" and {332}<113> twins can be activated in a grain. Then the primary SIM alpha" can be further transformed into {130}<310>(alpha") twins. With the further increase of strain, some {130}<310>(alpha") twins can continue to be transformed into secondary {332}<113>(beta) twin and some primary {332}<113> twins can also produce secondary alpha" to continue the deformation. When necking, a large number of {111}(alpha") twins are activated to further coordinate the plastic deformation. In addition, the multiple necking phenomenon is due to the further activation of {332}<113> twins and SIM alpha" during the necking of a certain area due to stress concentration during the stretching process, which causes local strengthening and resulting in the stop of necking. Finally, the serrations on the stress-strain curve may be caused by multiple necking.