Intercritical Rolling Induced Ultrafine Lamellar Structure and Enhanced Mechanical Properties of Medium-Mn Steel

The medium-Mn steel with ferrite and austenite structure was rolled in the intercritical region down to dif- ferent rolling reduction. The microstructure and mechanical properties of the rolled steels were investigated by scan- ning electron microscopy, transmission electron microscopy, X-ray diffraction and tensile tests. It was found that the ferrite and austenite structure gradually evolved into an ultrafine structure from the random directional lath structure to lamellar structure with lath longitudinal direction parallel to the rolling direction with increasing rolling strain. It was found that the thickness of the laths was gradually refined with increasing rolling strain. The lath thickness is about 0. 15 9m stored with high density dislocations and the austenite volume fraction of the steel is about 24% after 80% rolling reduction. Furthermore, it was interesting to find that yield strength, tensile strength and total elongation of the 80% rolled medium-Mn steel are about 1000 MPa, 1250 MPa and 24%, respectively, demonstrating an excellent combination of the strength and ductility. Based on the microstructure examination, it was proposed that the grain refinement of the medium-Mn steels could be attributed to the duplex structure and the low rolling temperature. Analysis of the relationship between the microstructure and the mechanical properties indicated that the high yield strength mainly resulted from the ultrafine grain size and the high density dislocation, but the improved ductili- ty may be attributed to the large fractions of austenite retained after intercritical rolling.

Annealing and optical homogeneity of large ZnGeP_(2) single crystal

A high-quality ZnGeP_(2)(ZGP)single crystal with large size ofΦ30 mm×80 mm was grown by a modified vertical Bridgman method.ZGP wafers were annealed with ZGP polycrystalline powder for 300 h at 550,600 and 650℃,respectively.The as-grown and annealed crystals were characterized by X-ray diffraction(XRD)analysis,Fourier transform infrared spectroscopy(FTIR),IR microscope and energy-dispersive spectroscopy(EDS).Results show that the quality of all wafers is improved evidently after annealing and the optimum annealing temperature obtained is 600℃.The IR transmittance of the wafer measured by FTIR is up to 56.78%at wavelength of 2.0μm nearby and exceeds 59.00%in the wavelength range of 3.0-8.0μm.The deviations from stoichiometry decrease,and the homogeneity of the crystal is also improved after annealing.In this paper,scanning infrared map was proposed as a new nondestructive method to evaluate optical quality and homogeneity of crystal through comparing the IR transmittance with the three-dimensional IR spectral contour map.

Novel fused-silica charge detection tile for particle detectors

Purpose Develop a novel charge-detecting tile for future large-scale liquid xenon TPC for searching for neutrinoless doublebeta decay.Methods Use advanced microelectronic technologies to fabricate small metal pads on a fused-silica wafer.The pads are chained into orthogonal strips,and the strips are isolated at the cross sections.The size of the pads defines the pitch between parallel strips and can be flexibly tuned according to any optimized dimension from future Monte Carlo studies.Such tile also has good potential to suppress the radioactivity and control electronics noise.Furthermore,its modular design allows to easily cover a large size.Results The design and performance have been demonstrated by a prototype tile,particularly by comprehensive tests in liquid xenon.Conclusions A new design of charge detection tile and the fabrication technologies have been developed,which would be useful for future noble liquid detectors.