| Summary: | 碩士 === 國立成功大學 === 材料科學及工程學系碩博士班 === 100 === This study focused on observing the evolution of texture and microstructure in the face-centered cubic (fcc) disordered phase of FePd alloys during cold rolling. Cold rolling can produce preferential orientation and small grain size. Therefore, the hard magnetic properties, such as coercivity, of the face-centered tetragonal (fct) ordered phases of FePd alloys will be improve after the fct phase transformation annealing.
Here, fcc phase of FePd alloys are cold rolled to moderate deformation (50% reduction) and high deformation (88% reduction). Then, the evolutions of texture and microstructure of fcc FePd alloys for 50% and 88% reduction would be analyzed by using x-ray diffraction (XRD) and electron backscatter diffraction (EBSD) techniques.
As the result of texture analysis form 50% to 88% reduction, preferential orientation of {220} is gradually increasing during cold rolling from 50% to 88% reduction. In addition to this, orientation densities of Brass {110}〈112〉 and Goss {011}〈100〉 are increasing. Copper {112}〈111〉 is not diminished instead of increasing. On the other hands, the orientation distribution functions (ODFs) for 50% and 88% obtained by EBSD compared with that by XRD. Therefore, the results of microstructure analysis by EBSD are confident with these by XRD. For the microstructure analysis, annealing twins of 〈111〉60o is widely observed as 46% fraction of twin at the reduction 0%. For 50% reduction, twin fraction has decreased to 12%. Deformation twins, deformation bands and transition bands have been observed at 50% reduction. For 88% reduction, twin fraction has increased to 20%. Micro-shear bands, deformation twins have been observed at 88% reduction. Average cell size decreases as 28.55 to 3.43m during cold rolling from 0% to 88%. In addition to those, dislocation slip, mechanical twinning and shear banding are considered to be the deformation mechanism after 88% cold rolling. Occurrence of Goss-oriented micro-shear bands are supposed to be the cause of increasing of Goss and Copper components at 88% reduction.
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