Microstructures,properties and high-temp oxidation behaviors of Ti-45Al-8Nb-xHf alloys
Ti-45Al-8Nb-xHf(x=0.5,1.0,1.5,2)alloys were prepared by argon-protected vacuum induc-tion melting process,and the microstructure,compressive properties and antioxidant properties of the al-loys were investigated by using optical microscope(OM),scanning electron microscope(SEM),energy spectrum spectrometry(EDS),X-ray diffraction(XRD)and universal testing machine.The results show that the increase of Hf element content can maintain and refine the microstructure of the alloys,delay the transformation of the tissue at high temperature,and increase the compressive strength and compres-sion ratio of the alloys to 1 923 MPa and 25.7％,respectively,with an increase of more than 30％,which has a significant strengthening effect.The alloys have a stable TiO2+Nb2O5 oxide sublayer when oxid-ized at 1 000 ℃,which grows by oxidation at a flat interface,the size of the oxide diffusion layer is stable less than 85 μm,the oxidized quality changes linearly,and the oxidation rate curve decreases and finally reaches the stable oxidation stage.The addition of appropriate amount of Hf is conducive to strengthening the mechanical properties of the alloys and high-temperature oxidation resistance.
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