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

采用透射电镜观察和基于组织能量计算和计算机模拟的理论分析方法，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。得到的主要结果如下：1) Ni-Al-Ti三元合金的γ′金属间化合物分解为γ′-基体+γ-析出相两相，γ析出相颗粒表现出一些看似奇怪的弹性约束体系的显微组织变化。2) Ti- al二元合金中Ti+Ti_3Al和TiAl+Ti_3Al_5的两相组织也出现了一些看似奇怪的组织变化，除非考虑弹性效应，否则无法理解。3)在弹性约束的Fe-Si-V合金中，嵌套在无序A2基体中的有序DO_3析出颗粒有时会分解。形成A2+DO_3两相状态，并且在DO_3沉淀颗粒中新出现A2颗粒并变粗，从而引起分裂现象。4)在弹性约束的Ni-Al-Ti合金中，嵌套在无序γ基体中的有序γ′析出颗粒有时也会分解为γ+γ′两相，γ′析出颗粒中出现新的γ粒子并变粗，从而引起分裂现象。5) Fe-Si-V和Ni-Al-Ti合金中有序析出相相分解形成的两相组织与通常的Ostwald成熟相比，表现出较慢的粗化。6)利用有序相（包括金属间化合物）的相分解和弹性能的作用（即弹性效应）对于获得耐热合金所需的稳定的两相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.