Acta Materialia journal: Solving the problem of refining aluminum alloys!

Grain refinement plays an important role in improving strong plasticity, casting quality and comprehensive quality of alloys. However, when the conventional grain refiners (such as Al-Ti-B) refine the aluminum alloy containing Si/Zr, the nucleation interface will be damaged by Si/Zr, and the phenomenon of Si/Zr refining "poisoning" will occur. The "poisoning" caused by Si/Zr refining is an urgent problem to be solved in the aluminum processing industry, which seriously restricts the development of high-strength aluminum alloy and hindersthe lightweight development of high-end equipment in aerospace, transportation and other fields. It has become a "pain point" in the transformation and upgrading of aluminum processing industry and high-quality development. 

The team of Professor Liu Xiangfa of Shandong University is committed to solving this problem. After more than ten years of systematic research, they have successfully independently developed Al-TCB crystal seed alloy which is resistant to Si/Zr refining "poisoning", and have realized industrial production and application. Recently, important progress has been made in revealing the mechanism of anti-refining "poisoning" : Al-TCB seed alloy has a large number of fine and uniformly dispersed TCB complexes, which are composed of B-doped TiC (B-TiC) and C-doped TiB2(C-TiB2). In aluminum melts, especially in aluminum-silicon melts, B-TiC in TCB complex evolves into Al4C3, releasing Ti atoms that help refine α-Al, and increasing the number density of C-TiB2 in nucleating substrate. Both experiments and first-principles calculations show that C doping in C-TiB2 reduces the tendency of segregation of Si or Zr at the C-Tib2 /Al interface, preserving the structure of TiAl3-2DC at the interface, and is still an effective nucleating substrate for α-Al. 

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