Ductility Improvement by Microstructural Control on Multiphase Intermetallic Alloys Using Phase

已经有几个例子表明，在多组分合金系统中，对相邻的具有不同有序晶体结构的金属间化合物相组成的显微组织的控制成功地提供了可观的室温拉伸塑性。然而，在这些情况下，由于高温下精细组织的不稳定，似乎很难同时获得足够的高温强度。本工作旨在通过在足够高的温度下相分解来开发多相金属间化合物合金，以便在1273K以上的温度下产生稳定的组织。选择Ni-Al-Mo系统作为合金系统，是因为似乎存在一个成分区域，在该区域中，B2相分解为LL2Ni3Al和α-Mo末端固溶体α(Mo)，在1573K左右，通过差热分析和显微组织观察对相图进行了评估，然后通过电弧熔炼制备了选定的合金。结果表明，某些合金，如Ani-22at%Al-8at%Mo合金，表现出优异的高温强度和一定的室温塑性。

There have been several examples in which the control in the microstructure consisting of intermetallic phases with different ordered crystal structure which are neighboring in the multi-component alloy systems was successful to provide appreciable tensile ductility at room temperature. However it seems in those cases to be difficult to achieve enough high temperature strength at the same time due to the instability of a fine microstructure at elevated temperatures.The present work is designed to develop multi-phase intermetallic alloys through a phase decomposition at a high enough temperature so that a microstructure produced would be stable at temperatures over 1273 K.The Ni-Al-Mo system was chosen as an alloy system because there seems to be a compositional region in which the B2 phase decomposes into the Ll_2 Ni_3Al and the alpha-Mo terminal solid solution, alpha(Mo), at around 1573 K.Phase diagram evaluation by differential thermal analysis and microstructural observation is followed by fabrication of selected alloys by arc-melting. It is then shown that some alloys, typically aNi-22at%Al-8at%Mo alloy, exhibits an excellent high temperature strength with some room temperature ductility.