The Effect of Cooling Rate from Solution on the Lattice Misfit During Isothermal Aging of a Ni-Base Superalloy
The Effect of Cooling Rate from Solution on the Lattice Misfit During Isothermal Aging of a Ni-Base Superalloy
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DOI：
10.1007/s11661-014-2197-1
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发表时间：
2014-01
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影响因子：
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通讯作者：
L. Connor;H. Stone;D. Collins;M. Preuss;M. Hardy;C. Rae
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文献类型：
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作者：
L. Connor;H. Stone;D. Collins;M. Preuss;M. Hardy;C. Rae
利用高分辨中子衍射研究了多晶镍基高温合金RR1000在时效热处理过程中晶格失配的演变过程。样品经过超溶剂热处理，然后在老化前以100或1 K min - 1的冷却速度冷却。无论冷却速度如何，晶格失配在整个时效循环中保持在约0.1%不变，表明微观结构保持稳定。显微结构观察证实了在1 K min−1冷却的样品的结果。然而，当冷却速率为100 K min−1时，次级γ′保持不变，而三级γ′则表现出明显的粗化。利用模拟衍射图研究了γ′分布的体积分数、粒径和晶格参数对测量的晶格失配的影响。结果表明，传统的测量晶格失配的方法将被体积分数最高的γ′分布所主导，因此可能会掩盖体积分数较低时γ′分布的细微变化。
The evolution of lattice misfit in the polycrystalline nickel-base superalloy, RR1000, has been investigated using high resolution neutron diffraction at interrupted time intervals during an aging heat treatment. Samples were subjected to a super-solvus heat treatment followed by either a 100 or a 1 K min− 1 cooling rate prior to aging. Irrespective of cooling rate, the lattice misfit remained unchanged at approximately 0.1 pct throughout the aging cycle, indicating the microstructure remained stable. Microstructural observations validated this result for samples cooled at 1 K min− 1. However, for the faster, 100 K min− 1, cooling rate, whilst the secondary γ′ remained unchanged, the tertiary γ′ showed significant coarsening. Simulated diffraction patterns were used to investigate the influence of volume fraction, particle size, and lattice parameter of individual γ′ distributions on the measured lattice misfit. The results obtained indicate that conventional methods of measuring lattice misfit will be dominated by the γ′ distribution with the highest volume fraction, and may therefore obscure subtle changes in the γ′ distributions with lower a volume fraction.