The Formation Mechanism of Nanocrystals after Martensitic Transformation.

Understanding the ultrafine substructure in freshly formed Fe-C martensite is the key point to reveal the real martensitic transformation mechanism. As-quenched martensite, whose transformation temperature is close to room temperature, has been investigated in detail by means of transmission electron microscopy (TEM) in this study. The observation results revealed that the freshly formed martensite after quenching is actually composed of ultrafine crystallites with a grain size of 1−2 nm. The present observation result matches well with the suggestion based on X-ray studies carried out one hundred years ago. Such nanocrystals are distributed throughout the entire martensite. The whole martensite shows a uniform contrast under both bright and dark field observation modes, irrespective of what observation directions are chosen. No defect contrast can be observed inside each nanocrystal. However, a body-centered cubic {112}<111>-type twinning relationship exists among the ultrafine α-Fe grains. Such ultrafine α-Fe grains or crystallites are the root cause of the fine microstructure formed in martensitic steels and high hardness after martensitic transformation. The formation mechanism of the ultrafine α-Fe grains in the freshly formed martensite will be discussed based on a new γ → α phase transformation mechanism.

Effective information processing method to produce a computer-generated hologram based on a spatial light modulator.

In this paper, we propose an effective information processing method to produce a computer-generated hologram (CGH) based on a spatial light modulator (SLM). The method generates CGHs according to the property of the field of view (FOV), which, to the best of our knowledge, has never been proposed before. The CGH is composed of essential interference patterns (EIPs). Each EIP records the information of different object points. The resolution of the EIP is reduced. In the reconstructed process, the boundaries of the diffraction light of each EIP and FOV of the reconstructed image are parallel with each other. Compared with the conventional method, the experiments here demonstrate that the effective reconstructed information in the FOV has no change, while the waste reconstructed information out of the FOV is decreased at any viewing distance. The CGH can reconstruct an image with high quality. Meanwhile, the computation burden of calculating the CGH is reduced with our method.