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

在显微组织能量计算和计算机模拟显微组织变化的基础上，通过透射电子显微镜观察和理论分析，研究了几种镍基、铁基和钛基合金中各种双相组织的形成和稳定性。得到的主要结果如下：1)Ni-Al-Ti三元合金中的γ金属间化合物分解为γ‘基γ-析出物的两相状态，γ析出物颗粒表现出一些具有弹性约束体系特征的奇怪的显微组织变化。2)Ti-Al二元合金中的Ti_3Al和TiAl_3Al_5的两相组织也表现出一些看起来奇怪的组织变化，除非考虑弹性效应。3)在弹性约束的Fe-Si-V合金中，有序的DO_3析出物颗粒嵌入无序的A2基质中。4)在弹性约束的Ni-Al-Ti合金中，有序的γ‘相颗粒有时会分解成两相状态的γ’，而γγ‘相颗粒又新出现并粗化在γ’相颗粒中，γ‘相颗粒与通常的奥氏熟化相比，Fe-Si-V和Ni-Al-Ti合金中有序相分解形成的两相组织粗化较慢。6)利用有序相(包括金属间化合物)的相分解和弹性能效应(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.