C-Axis tensile deformation of Ti 3Al with the DO 19 structure at room temperature

Abstract

The tensile deformation behavior of single crystals of Ti 3Al (Ti–25 at.% Al) deformed in tension parallel to the c-axis has been studied at room temperature as a function of the thickness of tensile specimens. While premature fracture always precedes any plastic flow when the specimen thickness is larger than 300 μm, a 0.3–0.4% plastic strain is observed when the specimen thickness is reduced to 150 μm. The slip plane observed in tension is {20 2 ̄ 1 ̄ } , which is different from {11 2 ̄ 1 ̄ } observed in compression. Assuming that slip on {20 2 ̄ 1 ̄ } occurs along 〈11 2 ̄ 6〉 , the critical resolved shear stress (CRSS) value is estimated to be 420 MPa, which is a little lower than 450 MPa obtained for slip on {11 2 ̄ 1 ̄ } . The slip plane selection depending on the sense of applied stress (i.e. tension or compression) and the relative magnitude of CRSS values are consistent with the reported results of atomistic studies on the core structure of 1/3〈11 2 ̄ 3〉 dislocations in a model h.c.p. lattice.