Development of Heat Resisting Alloys Based on the Nano-Structure Control by Utilizing Phase Decomposition.

通过透射电镜观察和基于微观结构能量计算和/或微观结构变化的计算机模拟的理论分析，研究了Ni基、Fe基和Ti基合金中各种两相组织的形成和稳定性。结果表明：（1）Ni-Al-Ti三元合金的γ'相分解为γ'相基体+γ相析出物的两相状态，γ相析出物颗粒呈现出一些奇异的弹性约束系统的微观结构变化;（2）Ti-Al合金中Ti+Ti_3Al和TiAl+Ti_3Al_5的两相组织，在一定温度范围内，随着温度的升高，合金中的γ相析出物颗粒的数量逐渐减少，合金中的γ相析出物颗粒的数量逐渐减少，合金中的γ相析出物颗粒的数量逐渐减少。Al二元合金也表现出一些看似奇怪的微观结构变化，这些变化只有在考虑弹性效应后才能理解。3）在弹性约束的Fe-Si-V合金中，嵌入无序A2基体中的有序DO_3沉淀颗粒有时会分解。4）在弹性约束的Ni-Al-Ti合金中，镶嵌在无序γ基体中的有序γ'析出相有时分解为γ+ γ'两相，γ'析出相中新出现并粗化γ粒子，5）Fe-Si-V和Ni-Al-Ti合金中有序相的相分解所形成的两相组织与通常的Ostwald熟化相比，其粗化速度较慢（包括金属间化合物）和弹性能效应（即弹性效应）对于获得耐热合金所需的稳定两相显微组织是非常重要和有用的。

The formation and the stability of various two-phase microstructures in some Ni-base, Fe-base and Ti-base alloys were investigated by means of transmission electron microscopy observations and theoretical analyses based on the energy calculations of microstructures and/or computer simulations of microstructural changes. The main results obtained are as follows.1) The γ' intermetallic compound of a Ni-Al-Ti ternary alloy decomposes into a two-phase state of γ'-matrix+γ-precipitate and the γ precipitate particles exhibit some seemingly strange microstructural changes characteristic of the elastically constrained systems.2) Two-phase microstructures of Ti+Ti_3Al and TiAl+Ti_3Al_5 in Ti-Al binary alloys also exhibit some seemingly strange microstructural changes which cannot be understood until the elasticity effects are taken into consideration.3) In elastically constrained Fe-Si-V alloys, ordered DO_3 precipitate particles embedded in a disordered A2 matrix sometimes decompose. into a two-phase state of A2+DO_3, and A2 particles newly appear and coarsen in the DO_3 precipitate particles, which causes the splitting phenomenon.4) In elastically constrained Ni-Al-Ti alloys also, ordered γ' precipitate particles embedded in a disordered γ matrix sometimes decompose into a two-phase state of γ+γ', and γ particles newly appear and coarsen in the γ' precipitate particles, which causes the splitting phenomenon.5) Such two-phase microstructures formed by phase decomposition of ordered precipitates in Fe-Si-V and Ni-Al-Ti alloys exhibit some slower coarsening as compared with the usual Ostwald ripening.6) Utilizing the phase decomposition of ordered phases (including intermetallics) and the effects of elastic energies (i.e. the elasticity effects) is very important and useful to obtain the stable two-phase microstructures desirable to heat resisting alloys.