Flow stress,yield criterion and constitutive equation of mushy/semi-solid alloys

New mathematical models of yield criterion and constitutive equations of mu shy/semi -solid alloys (hereinafter described as semi -solid alloys) are pr oposed in order to investigate their flow features and deformation characte ristics in various forming and shaping processes. First, a large number of uniaxial compression tests of semi -solid alloys are carried out and their stress -strain curves are measured. Through the tests, the remarkable drop of their flow stress is observed when their solid fraction decreases from 1 00%. The second, a new formula of yield criterion of semi -solid alloys is proposed. It can express the drop of their flow stress in semi -solid state . In addition, so -called constitutive equations, which describe flow and d eformation of such alloys in forming and shaping processes, are derived fro m the formulated yield criterion. At the last stage, the obtained constitut ive equations are introduced to 3D FEM simulation of upsetting of billets.