Determination of forming ability of high pressure die casting for Zr-based metallic glass

Large-sized industrial grade Zr55Cu30Ni5Al10 bulk metallic glass (BMG) was fabricated by a two-step arc melting process and adding a trace of rare earth yttrium elements. A model to calculate critical cooling rate for forming BMG was established by considering the effect of pressure. Based on the model, the most important indicator, namely the critical size of forming BMG, for design and fabrication of BMG components by high pressure die casting (HPDC) is determined in consideration of different processing parameters, including the pressure and casting temperature. Theoretical calculation and numerical simulation indicated that increasing applied pressure during casting suppresses the nucleation of crystal nuclei but has little effect on the growth of nuclei at a deep supercooled temperature, thereby decreasing critical cooling rate and thus increase critical size. An increasing casting temperature would reduce critical size caused by more heat to dissipate. The critical size of the optimiZed Zr55Cu30Ni5Al10 BMG cast by using steel mold is determined to be about 4-7 mm under different HPDC parameters. Our study reveals that the forming ability of HPDC is large enough for fabricating low cost Zr-based BMGs with suitable size for applications. (C) 2017 Elsevier B.V. All rights reserved.