Determining the Hot Workability and Microstructural Evolution of an Fe-Cr-Mo-Mn Steel Using 3D Processing Maps.

The Laasraoui segmented and Arrhenius flow stress model, dynamic recrystallization (DRX) model, grain size prediction model, and hot processing map (HPM) of Fe-Cr-Mo-Mn steels were established through isothermal compression tests. The models and HPM were proven by experiment to be highly accurate. As the deformation temperature decreased or the strain rate increased, the flow stress increased and the grain size of the Fe-Cr-Mo-Mn steel decreased, while the volume fraction of DRX (Xdrx) decreased. The optimal range of the hot processing was determined to be 1050-1200 °C/0.369-1 s-1. Zigzag-like grain boundaries (GBs) and intergranular cracks were found in the unstable region, in which the disordered martensitic structure was observed. The orderly packet martensite was formed in the general processing region, and the mixed structure with incomplete DRX grains was composed of coarse and fine grains. The microstructure in the optimum processing region was composed of DRX grains and the multistage martensite. The validity of the Laasraoui segmented flow stress model, DRX model, grain size prediction model, and HPM was verified by upsetting tests.

Transparent and Planar Cs3Cu2Cl5 Crystals for Micrometer-Resolution X-ray Imaging Screen.

Copper-based (I) halide perovskites have emerged as a promising candidate for scintillation screens in X-ray inspection and imaging areas due to their solution processability and high light yield. Here, a centimeter-sized Cs3Cu2Cl5 single crystal was grown by a slow-cooling method. The planar orientation was controlled in a space-confined chamber, generating a planar crystal which is readily used for a scintillation screen without any further shaping. The crystal exhibited a unity photoluminescence quantum yield and superior scintillation performance. The Cs3Cu2Cl5 single crystal exhibited a high light yield up to 95,000 photons/MeV, which enabled an X-ray detector of a detection limit down to 2.7 µGyair/s. The homemade imager demonstrated a spatial resolution of 105 lp/mm, representing an unprecedented micrometer resolution in laboratory. Importantly, the stability of Cs3Cu2Cl5 was significantly improved by a new surface passivation procedure, whereby the passivated crystal reserved its phase after 6 months' storage in a vial. This work introduced a new solution-based synthetic method for two-dimensional scintillating crystals, opening many avenues to high-performance X-ray imaging applications.