Effect of Cooling Condition on Zr-Rich Core Formation and Grain Size in Mg Alloy

Abstract

The effects of cooling condition on the Zr-rich core formation and grain size in Mg-Zr alloys were investigated in this study. Four moulds with various cooling rates and different Zr additions were used. The results show that when Zr addition was 1.2%, the Zr-rich cores were round and their diameters increased with decreased cooling rates. When Zr addition content was decreased to 0.7%, Zr-rich cores formed only in the sand mould with the lowest cooling rate used in this study, and the morphology changed to rosette-like. The influence of cooling rate on grain size of Mg-Zr alloys was also investigated.

Effect of Melting Process on Zr Content and Grain Refinement in ZE41A Alloy

“…Various zirconium was added to the melt in the form of Mg-Zr master alloy preheated at 250˚C. The morphology and distribution of Zr particles in Mg-Zr master used was given in detail in Ref [8]. RJ 2 cover flux(main compositons:38-46% MgCl 2 ,32-40%KCl, 5-8%BaCl, 3-5%BaCl, 3-5%CaF 2 , and 8% NaCl+CaCl) was used as a mixed protection and RJ5 flux(main compositons:24-30% MgCl 2 , 20-26%KCl, 28-31%BaCl 2 , 13-15%CaF 2 , and 8% NaCl+CaCl) was used as refining agent.…”

Recent Advances in the Grain Refinement Effects of Zr on Mg Alloys: A Review

“…Generally, increasing the cooling rate (Ṫ) results in a decrease in grain size. For example, Liu et al [62] showed that the grain size of Mg-Zr binary alloys (0.3, 0.7 or 1.2Zr) decreased with increasing cooling rate from sand mold to Cu mold. Sun et al [63] found that the relationship between the grain size of Mg-Y-Zr alloy (1~9Y, 0.1~0.5Zr) and 1 𝑄𝑇 ⁄ could be linearly fitted at a cooling rate ≤80 °C/s (Figure 9 shows Mg-1Y-Zr alloy as an example of this phenomenon).…”