Comparison of Different Phase Contents in Ti-22Al-25Nb Alloy After Various Heat Treatments and Their Effects on the Microhardness of the Alloy
By designing different heat treatment processes for Ti-22Al-25Nb alloy,two-phase alloys consisting of β/B2 and O phases,as well as three-phase alloys consisting of β/B2,α2,and O phases,were obtained.The microstructural evolution,phases,phase volume fractions,and microhardness of the alloy under different heat treatment processes were investigated by using X-ray diffraction(XRD),scanning electron microscopy(SEM),and Vickers microhardness tester.The results showed that with decreasing the heat treatment temperature,the grain size of O and β/B2 phases in the Ti-22Al-25Nb alloy composed of β/B2 and O phases gradually increased;the volume fraction of O phase increased while the volume fraction of β/B2 phase decreased;and the microhardness of the alloy gradually increased.With decreasing the heat treat-ment temperature,the grain size of α2 and O phases in the Ti-22Al-25Nb alloy composed of β/B2,α2,and O phases gradually increased,while the grain size of β/B2 phase gradually decreased;the volume fraction of α2 and O phases in-creased,while the volume fraction of β/B2 phase decreased;and the microhardness of the alloy gradually increased.These results provide data reference for obtaining Ti-22Al-25Nb alloy with excellent comprehensive performance.
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