Influence of Rare-Earth Metals on the High-Temperature Strength of Ni_3Al-Based Alloys

摘要

The influence of the content of reaction- and surface-active alloying elements (rare-earth metals　(REMs)) and the method of their introduction into cast high-temperature γ'-Ni_3Al-based intermetallic alloys, which are thermally stable natural eutectic composites, on their structure–phase state and the mechanical properties is studied. The life of low-alloy heterophase γ' + γ cast high-temperature light Ni_3Al-based alloys is shown can be increased at temperatures exceeding 0.8T_m (T_m is the melting temperature of Ni_3Al) due to additional stabilization of the single-crystal structure of these alloys with submicron and nanometer-sized particles of the phases formed by refractory and active REMs. It is also shown that stage-by-stage fractional introduction of all components into alloys during vacuum induction melting with allow-ance for their reaction activities (most refractory metals are introduced in the form of low-melting-point master alloys at the first stage of vacuum induction melting, and lanthanum is introduced with a master alloy in the optimal contents of 0.1–2 wt % into the charge of VKNA-1V and VKNA-25 alloys at the final stage)leads to the formation of a modified structure stabilized by nanoprecipitates of nickel and aluminum lan-thanides and the phases formed by refractory metals. This method increases the life of VKNV-1V-type alloys (0.5 wt % Re) at 1000–1200℃ by a factor of ～1.7 and that of VKNA-25-type alloys (1.2 wt % Re and Co) by a factor of ～3.