A new approach to improving the macrosegregation in zirconium‐containing magnesium‐lithium alloy

Abstract

In the preparation process of zirconium‐containing magnesium alloy, although zirconium is introduced into alloy by magnesium‐zirconium master alloy, the settling of zirconium particles has always been a key problem. In this study, the magnesium‐30wt.%zirconium master alloy was added into magnesium‐14wt.%lithium‐zinc alloy melt in the form of the block (about 20 mm) and the particles (about 20 μm), respectively, and then magnesium‐14wt.%lithium‐zinc with 0.5 wt.% zirconium alloy were prepared using stir‐casting process. Macrosegregation of major element (zirconium), microstructure and microhardness at different casting positions were examined to investigate the effect of zirconium addition methods on macrosegregation of magnesium‐14wt.%lithium‐zinc alloy. The results show that, for the block magnesium‐zirconium master alloy addition, there is obvious macrosegregation in alloy ingots, the zirconium contents at the top position of ingot are higher than that at the bottom by nearly 200 %. The method of particles master alloy addition can effectively improve macrosegregation, the difference in zirconium contents between the top and bottom is less than 16 %.

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

“…Therefore, the Zr particle size distribution in the Mg-Zr master alloy needs to be controlled to be as fine and as uniform as possible. To achieve this aim, a new Mg-Zr master alloy with fine Zr particles [14,80] has been developed, and pre-treatments [27,[81][82][83][84][85][86][87] have been conducted to modify the Mg-Zr master alloys already available. In addition, melt treatment can be conducted to reduce the settling of Zr during the melting of the Mg alloy, thereby improving the Zr grain refinement efficiency [41,49,[88][89][90][91][92][93][94].…”

“…The severe plastic deformation (SPD) method can generate massive force, breaking the Zr particles into smaller ones, and can been conducted via hot rolling [27,83], equal channel angular extrusion (ECAE) [47,82,83], friction stirring processing (FSP) [84], or crush [85].…”

“…Wang et al [84] showed that FSP can be used to modify the Zr particle distribution of the Mg-30Zr master alloy. Recently, Wang et al [85] employed a new method for preparing "powder Mg-Zr master alloy" that consisted of three steps, i.e., mechanically crushing the original Mg-30Zr master alloy block, ball-milling the pieces, and finally sieving to keep particles smaller than 20 µm.…”

“…As a result of modification, the settling of Zr particles during melting can be retarded, and a higher soluble Zr content can be obtained. Consequently, the grain refinement efficiency of pretreated Mg-Zr master alloys on pure Mg [81][82][83], Mg-10Gd-3Y [27], Mg-3Nd-0.2Zn [84] and Mg-14Li-Zn [85] alloys was effectively improved. However, the pretreatment methods have some obvious disadvantages, such as their complicated processes, low productivity, and the SPD molds and tools (FSP probes) being easily broken.…”

“…A similar method was also reported by Zhang et al [95], who improved the refining efficiency of Al-5Ti-1B master alloy on Al alloys by re-precipitating tiny TiB 2 particles. on pure Mg [81][82][83], Mg-10Gd-3Y [27], Mg-3Nd-0.2Zn [84] and Mg-14Li-Zn [85] allo was effectively improved. However, the pretreatment methods have some obvious dis vantages, such as their complicated processes, low productivity, and the SPD molds a tools (FSP probes) being easily broken.…”