Deformation characteristics at 300 K of single-crystalline molybdenum sheet prepared by secondary recrystallization

The present work was carried out to examine the slip behavior under tension and the role of island grain on the deformation and fracture in a Mo single crystal. The tensile deformation characteristics of single-crystalline molybdenum sheet containing Ca and Mg of 50ppm and oxygen of 270ppm, which was prepared by secondary recrystallization, were investigated at 300 K and compared with that of the crystal containing a low level of oxygen (10ppm) in view of slip geometry and fracture behavior. Stress was applied approximately in the [011] direction. Conclusions are as follows: (1) slip system of (bar 312)[111] dominated deformation at the beginning of yield and this slip system continued up to a strain of 0.09; (2) (bar 211)[111] and (bar 1 bar 12)[111] began to act as another vital slip systems at a strain over 1.00; (3) stress drop phenomenon at a strain of 0.10 might be due to the change of slip system from (bar 312)[111] to (bar 211)[111] and/or (bar 1 bar 12)[111] by the rotation of crystal axis against the tensile axis; (4) cracks were generated from the island grain having different orientations from the matrix and separated from the matrix intergranularly. Subsequently the crack propagated along the (bar 1 bar 12) plane. It might be attributed to the pile-up of dislocations and the grain boundary weakening by the segregation of oxygen