Effect of hot rolling on the microstructure and fracture behavior of a bulk fine-grained W-Y2O3 alloy

The effect of hot rolling on the microstructure and fracture behavior of a bulk W-Y2O3 alloy was studied. The as-sintered compact was comprised of polyhedral tungsten grains with an average grain size of 4 μm, spherical Y2O3 disperoids and trace amount of nano-sized/submicron pores. It showed typical inter-granular fracture. After hot rolling, it was observed that the tungsten grains were elongated along the rolling direction, showing much severe deformation than Y2O3 particles. The residual pores were reduced. The as-rolled alloy showed obvious anisotropic fracture behavior. For the longitudinal specimens, the fracture mode could be totally transformed to trans-granular cleavage fracture. Three point bending test showed that the longitudinal specimens of the bulk W-Y2O3 alloy performed appreciable ductility and superior fracture strength (2152.7 MPa) as compared to the as-sintered alloy (brittleness, 543.4 MPa) and transverse specimens (brittleness, 1105.0 MPa). The responsible strengthening and toughing mechanisms were analyzed and presented.