Abstract
A 0.4C-2Si-1Cr-1Mo steel with an ultrafine elongated grain (UFEG) structure and an ultrafine equiaxed grain (UFG) structure was fabricated by multipass caliber rolling at 773 K and subsequent annealing at 973 K. The impact and tensile properties were investigated. The microstructures in the rolled bars consisted of UFEG structure with a strong α-fiber texture. The rolled bar consisting of spheroidal cementite particles that distributed uniformly in the elongated ferrite matrix of transverse grain size of 0.26 μm exhibited excellent strength - toughness balance. On the other hand, the annealed sample which consisted of UFG structue of 0.5 μm with similar α-fiber texture decreased not only strength but also toughness. In conclusion, the strength-toughness balance is improved by refining crystal grains and controlling their shape and orientation.
