Development of A New Type of Functional NiAl-base Alloys

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The beta phase of nickel and cobalt aluminides with B2-type (C_sC1) structure have the potential to serve as a new type of materials with multi-functional properties such as high temperature strength, good oxidation resistance, shape memory, high damping capacity, stc. However the lack of ductility limits their application as the functional materials. The aim of this project is to develop a new type of beta base multi-functional materials improved ductility by microstructural control.1.Thermodynamic AnalysisThe phase equilibria of the Ni-rich portion in the Ni-Al-Mn, Ni-Al-Co and Ni-Al-Fe systems have been experimentally determined, and thermodynamic analysis on basis of the experimental data have been done.2.High Temperature MaterialsBy means of microstructural control due to the information of the thermodynamic analysis, ductile gamma'(L1_2)+beta two-phase alloy which has both excellent oxidation resistance and high temperature strength has been developed by the conventional fabrication method combined with a thermomechanical heat treatment.3.Shape Memory and Damping MaterialsMartensitic transformation temperatures in the beta phase B2*L1_0 (Ms) of the Ni-Al-X (X : Ti, V,Cr, Mn, Fe, Co, Cu, etc.) systems were determined by DSC.It was clarified that adding Mn, Fe and Co are useful to increase the Ms temperature. By means of these data of Ms and phase equilibria, ductile gamma(Al)+beta two-phase shape memory alloys which operate at high temperatures between 100 and 600ﾟC have been developed in the Ni-Al-Fe-Mn quaternary system. These two-phase shape memory alloys show not only high damping capacity, but also higher yield strength than the other damping materials.