Forgeability and die-forging forming of direct chill casting Mg–Nd–Zn–Zr magnesium alloy

Abstract

Mg–3.0Nd–0.2Zn–0.4Zr (wt.%, NZ30K) is a newly developed magnesium rare earth alloy with middle strength and high toughness in as-cast state. In this paper the forgeability of the as-cast NZ30K alloy prepared by direct chill (DC) casting was studied. The forgeability of the DC casting NZ30K alloy was firstly modeled by using uniaxial tensile and compression tests at temperatures between 250 and 400 °C and strain rates ranging from 0.001 to 10 S −1. The results show that the optimum forging temperature of the as-cast NZ30K alloy is between 350 and 400 °C and strain rate ranges from 0.01 to 1 S −1. Finally, a flange of automobile clutch was tentatively and successfully forged by using the DC casting NZ30K billet. The forged flange possesses desired microstructure and high mechanical properties. The mechanical properties of the product are further enhanced by T5 heat treatment for precipitate strengthening. The maximum ultimate tensile strength, yield strength and elongation of the T5 state alloy are 323.5 MPa, 318.2 MPa and 11.2%, respectively. The creep strain rates for the NZ30K alloy are 2.0 × 10 −8 and 1.2 × 10 −7 at the 200 and 250 °C, respectively.