| Summary: | 碩士 === 國立屏東科技大學 === 機械工程系所 === 95 === The main purpose of the present studies are to investigate the microstructures of the Ti-4.5Al-1.5Mo-1.2V-0.5Fe alloy by using of optical microscope, scanning electron microscope and transmission electron microscope. Based on the present study, some results are described as followings:
1.Being heat-treatment in the ranges of 800~960℃, the microstructures of the alloy are essentially a α and β phase. In addition, the β grain size would be increased as the temperature. Being heat-treatment above 890℃, the microstructures of the alloy are essentially a α and β phase. In addition, some particles with martensite structure could be observed. This result has been reported by other workers on the Ti-Al-V alloy system.
2.Being heat-treatment in the ranges of 800~1100℃, the phase transformation of the alloy are β + α → β + α + α/ → β + α/, didn’t observed ω and α// phase.
3.In the study phase transform point of Ti-4.5Al-1.5Mo-1.2V-0.5Fe alloy is about 980℃. Being heat-treatment above 980℃ quenching in water, the Fe & Si elements could melt in β phase completely, to avoid segregating to debase mechanical properties.
4.In the study the specimens processed low temperature solution heat treatment and aging heat treatment, the OM found globular particle of β in the matrix become black, and we could observe that Widmanstätten side-plate separate from grain boundary. Being aging heat-treatment for long, the Widmanstätten side-plate could transform α & β structure, didn’t observed ω phase. The highest hardness is about Hv462.
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