The transverse elongation and fracture mechanism of the upset Mo and Mo-La2O3 bars

The transverse elongation and structure of pure molybdenum and Mo-La2O3 bars manufactured by a repeatedly forge, upset technique and annealing at different temperatures were investigated at room temperature. The results show that the transverse elongation of the as-deformed molybdenum bars is 5%, while that of the Mo-La2O3 bars is 2%. After annealed, both the transverse elongation of two bars is improved. The elongation of molybdenum bars reaches the maximum value of 10% at 1253 K and that of Mo-La2O3 bars is 12.5% at 1473 K for 1 h. Most of the transgranular fractures, characterized by a large amount of cleavage planes and river patterns, are formed during the bending process. A lot of small dimples can also be seen in the view, and the diameter is about 2 μm. Meanwhile, the fracture shows a ductile laminate fracture mechanism. The fracture mechanism of annealed molybdenum and Mo-La2O3 alloy can be explained by the proposed model.