Coarsening and Microsegregation during Solidification of Ni-AI-Cr Dendritic Monocrystals
Coarsening and Microsegregation during Solidification of Ni-AI-Cr Dendritic Monocrystals
复制标题
Ni-Al-Cr枝晶单晶凝固过程中的粗化和微观偏析
DOI：
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发表时间：
1982
期刊：
影响因子：
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通讯作者：
A. F. Giamei
中科院分区：
文献类型：
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作者：
J. J. Montoya;R. Kadalbal;T. Z. Kattamis;A. F. Giamei
在8 × 103和20 × 103 K/m的梯度下，以0.05 ~ 2.00m/h的速度定向凝固富镍Ni-Al-Cr合金枝晶单晶。结果发现，如果生长是细胞枝晶，细胞枝晶间距表现出相同的依赖于生长速率或局部冷却速率的柱状枝晶中的二次枝晶臂间距。枝晶固体的等温粗化动力学的研究表明，在铬或铝浓度的增加减缓粗化，产生更精细的铸造显微组织。在相同的原子浓度增量下，铬对枝晶组织的细化作用比铝大。随着局部冷却速率的增加，最大溶质浓度基本不变，最小溶质浓度略有下降，偏析比略有增加，非平衡枝晶间γ′相的体积分数显著增加。在以较高速率生长的晶体中，该相在晶体提拉期间溶解得更快。从理论和实验两方面建立了铝和铬的均匀化动力学。为了达到相同的指标或残余偏析，铬比铝需要更长的时间。
Dendritic monocrystals of nickel-rich Ni-AI-Cr alloys were directionally solidified at rates ranging from 0.05 to 2.00 m per hour, under gradients of 8 × 103 and 20 × 103 K per meter. It was found that if growth is cellular dendritic, the cellular dendritic spacing exhibits the same dependence on growth rate or local cooling rate as does the secondary dendrite arm spacing in columnar dendrites. A study of the isothermal coarsening kinetics of the dendritic solid indicated that an increase in chromium or aluminum concentrations slowed down coarsening, yielding finer cast microstructures. At equal atomic percental increase in concentration the effect of chromium was more significant than that of aluminum in refining the dendritic structure. With increasing local cooling rate the maximum solute concentration remained practically constant, the minimum solute concentration slightly decreased, the segregation ratio slightly increased, and the volume fraction of nonequilibrium interdendritic γ′ phase increased substantially. This phase dissolved during crystal pulling faster in crystals that were grown at a higher rate. The homogenization kinetics of aluminum and chromium were established both analytically and experimentally. A longer time was necessary for chromium than for aluminum in order to achieve the same index or residual segregation.