Microstructure and mechanical properties of as-cast Ti-6Al-xMo alloys
As-cast Ti-6Al-xMo(x=0,4,8,12,16 and 20 mass％)alloys were prepared by non-consumable vacuum arc melting furnace.Microstructure and mechanical properties of the Ti-6Al-xMo alloys with different Mo contents were studied by means of X-ray diffraction(XRD),optical microscope(OM),scanning electron microscopy(SEM),hardness test and compressive test.The results show that with the increase of Mo element content,the phase structure of the alloys changes from α → α'+β → α"+β → β.The microstructure of the Ti-6Al alloy consists of unevenly distributed lamellar α phase.When the content of Mo element is 4 mass％,obviousβ grain boundaries and acicular α'martensite phase appear in the alloy.When the content of Mo element increases to 12 mass％,acicularα"martensite phase and discontinuous sub-grain boundaries appear in the alloy.When the content of Mo element increases to more than 16 mass％,the microstructure of the alloy is composed of coarse equiaxed β grains.The stress-strain curve of the as-cast Ti-6Al alloy shows"PLC effect".The compressive plasticity of the Ti-6Al-16Mo and Ti-6Al-20Mo alloys exceeds 50％but still does not fracture,showing good plasticity.The fracture morphology shows that all alloys exhibit ductile fracture after the addition of Mo element.
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