| Summary: | 碩士 === 國立屏東科技大學 === 機械工程系所 === 97 === The purposes of the studies are to investigate the phase transformations, mechanical properties and microstructures of Fe-5Cr-4.5Ni-2Mo-0.5Ti-0.3Al-0.2C alloy by use of X-ray diffraction (XRD), optical microscope (OM) and transmission electron microscope (TEM). Some results are described as
following: Being SHT, the ultimate tensile strength, yielding strength and elongation of the alloy are in the range of 965-1380 MPa, 930-1260 MPa, 6.5-3.8 %, respectively. After aged at 450-650 ℃ for various times, the ultimate tensile strength, yielding strength and elongation of the alloy are in the range of 1180-1690 MPa, 1040-1520 MPa, 17.0-8.2 %, respectively. Being solution heated treatment at 1100℃/1 H, the microstructure of the alloy is a plate martenite phase belonging to the B.C.C. structure. In addition, some TiC carbides were found within the matrix. When aged at 450 ℃ for various times, some α-phase precipitates had been found. And, increasing the aging
temperature to 550℃, it can be observed that the L12 -type precipitates formed within the matrix. Age 650-750 ℃ for various times, the M23C6-type carbides and austenite phase formed.
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