The effects of Yttrium on the microstructure of Ti-23Al-25Nb alloy have been studied by OM,XRD,XRF,SEM,EPMA and TEM.The results show that the microstructure of two casting alloys is orthorhombic phase(O-phase).Yttrium has obviously refined the grain size of the alloy,where the Ti-23Al-25Nb grain size within a range of 400-600μm,and the Ti-23Al-25Nb-0.36Y grain size within a range of 40-100μm,refined to about 6-8 times.By BSE and TEM,it is found that the Y2O3 lies in the interior of grains and along grain boundary in Ti-23Al-25Nb alloy.Base on the forming mechanism of O-phase and theory of grain refinement,the effects of Yttrium on the refinement process of O-phase have been analyzed.
Key words
Ti-23Al-25Nb alloy /
Yttrium /
microstructure /
refinement grain
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