查看更多>>摘要：The mechanism behind void formation during superplasticity remains a subject of uncertainty.This study presented a novel insight into the void formation in a fine-grained Ni-Co-based superalloy during superplasticity.It was observed that the dissolution of γ'-particles resulted in the creation of vacancies due to differences in atomic size between the matrix and the particles.These vacancies acted as inclusions,leading to the formation of micro-voids.Notably,excessive void formation correlated with higher particle dissolution was experimentally observed,highlighting a direct relationship between void formation and particle dissolution.
查看更多>>摘要：At present,improving the properties of aluminum alloys is generally achieved by increasing the cooling rate of the melt and adding micro-nano particles.Controlling the cooling rate of the melt to improve the refining effect of grain refiner is still a dif-ficult problem in the aluminum alloy casting industry.An innovative and environmentally friendly casting process,known as freeze ablation,was introduced during the preparation of an Al-NbB2 intermediate alloy.This process significantly enhanced the cooling rate of the melt.The results indicated that the Al-NbB2 intermediate alloy produced under high cooling rates had a noticeable refining effect on Al-Cu alloys,with smaller NbB2 particles demonstrating superior refining performance.The average grain size of the refined Al-Cu alloy decreased from 154 to 69 μm,the tensile strength increased by 12％,the fluidity increased by 18.4％,and the hot tearing index decreased from 144 to 12.The matching degree between NbB2 and α-Al was calculated using high-resolution transmission electron microscopy and the edge-to-edge model.It was found that the atomic interplanar spacing and the interatomic spacing mismatch between NbB2's<11(2)0>plane and Al were both less than 10％,which further proved that NbB2 could serve as an effective nucleation site for α-Al grains to achieve grain refinement.
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