Abstract
Si-poisoning and fading effect of grain refiners deteriorate the refining effect of Al-Si alloys (Si≥3 wt%), further worsening the performance of alloys. In this work, an innovative Al-Nb-Ti-B with anti Si-poisoning and anti-fading properties was prepared by introducing synthetic TiB2 into Al-Nb melt. At the cooling rate of 1.4 K/s, the average grain size of Al-7Si alloys inoculated by this Al-Nb-Ti-B was refined to 326.05 μm, 40% reduction compared to 549.06 μm by commercial Al-5Ti-1B. The grain size remained at 421.95 μm even after 120 min holding time. Anti-fading mechanism was investigated by size distribution analysis of TiB2 nucleating particles. Anti Si-poisoning mechanism is attributed to Nb element which accumulates on the (01—10) surface of TiB2 and reduces the lattice misfit between TiB2 and α-Al. Atomic-scale microstructure analysis and first-principles calculations reveal that the Nb enrichment on TiB2 increases the chemical affinity of TiB2/Al interface and decreases the Si adsorption propensity. In brief, appropriate size distribution and unique Nb-rich layer contribute to the excellent grain refinement of TiB2 particles modified by Nb. These findings may shed new light on the realm of innovative aluminum grain refiners.
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