Processing, microstructure, and properties of beta-CEZ

For the beta-CEZ material, some of the important processing parameters to establish a necklace type of microstructure by through-transus deformation were evaluated with respect to optimizing fracture toughness and yield stress level. In addition, bi-modal microstructures which can be produced by conventional alpha + beta processing were evaluated. For the necklace microstructure a high fracture toughness value of 68 MPa m(1/2) at a yield stress level of 1200 MPa was reached in forgings, but the fracture toughness was anisotropic dropping to 37 MPa m(1/2) in the short transverse direction. For the bi-modal microstructure an isotropic fracture toughness value of 37 MPa m(1/2) at the same yield stress level of 1200 MPa was reached without major difficulties.