Effect of cold rolling deformation on low temperature phase transformation behavior of metastable β-type Ti-B20 titanium alloy
The phase composition and microstructure evolution of Ti-B20 titanium alloy in different states during low temperature aging were studied using optical microscope(OM),scanning electron microscopy(SEM),X-ray diffraction(XRD)and transmission electron microscopy(TEM),and the formation law of ω phase during low temperature aging was analyzed.The results show that the isothermal ωphase with two orientations is preferentially precipitated in the metastable β phase of the solution treated Ti-B20 alloy during low temperature aging.When the aging temperature increases to 450 ℃,the ω phase disappears.The crystal defects such as dislocations formed during the cold rolling deformation of the alloy reduce the required energy for the phase transformation of the alloy,promote the formation of the ω phase,and narrow the temperature range of the ω phase.The larger the deformation,the greater the promotion effect.The phase composition of ST sample,CR10 sample and CR50 sample after aging at 350 ℃ for 1 h are β+ω,β+ω+α and β+α,respectively.When β,ω and α coexist,the orientation relationship between them is:[011]β//[2(1)(1)0]ω//[000(1)]α.
Ti-B20 titanium alloycold rolling deformationisothermal ω phasephase transformation behavior
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