Research progresses on anti-Si/Zr-poisoning in high-performance Al alloys: a review

Al–5Ti–1B master alloy is the most widely applied grain refiner for Al alloys. However, some essential alloying elements in high-performance Al alloys, such as Si and Zr, can cause the fading or failure of the refining effect, which is called Si/Zr-poisoning. This phenomenon can seriously restrict the improvement of comprehensive performances and lead to poor processability and high rejection rate of the products. To solve the above problems, the mechanisms of Si/Zr-poisoning and the corresponding coping strategies in high-performance Al alloys are highlighted, clarified and summarized by reviewing the latest research progresses in this work. In general, the poisoning mechanisms can be classified into efficacy losing of nucleating substrate during the grain nucleation stage and weakened growth restriction capabilities during the grain growth stage. The coping strategies carried out on the industrial site mainly include increasing addition level of refiners or pre-placing it in mold/casting trough, which can bring some new problems, such as generation of coarse compounds and increase in the scrap rate. Meanwhile, the progresses or breakthroughs in academia basically focus on the development of new refiners, improving existing master alloys and micro-alloying design, which have provided a variety of feasible paths to solve the poisoning problem, among which the Al-TCB master alloy can realize anti-Si/Zr-poisoning based on the dynamically evolving TCB complex. It is believed that the anti-Si/Zr-poisoning mechanisms and coping strategies will be renewed and enhanced persistently with the characterization and detection technologies driving forward.