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The method and mechanism of suppressing grain growth and microstructure coarsening in nickel-based alloy welded joints were studied herein. First, sodium thiosulfate was used to simulate the crystallization processes of the welding pool. Then, on this basis, the compound physical fields of low-frequency mechanical vibration and rapid cooling on the microstructure of the Inconel 601H alloy welded joint were investigated. Finally, the joint grain refinement behavior and mechanism were analyzed based on the experimental and physical simulation results. The experimental results indicate that only the low-frequency mechanical vibration acting in the welding process caused the center of the weld to be mostly composed of equiaxed grains. The epitaxial solidification phenomenon near the fusion line disappeared, but there were still many fine columnar grains in the upper part of the weld edge. The heat-affected zone (HAZ) morphology was eventually dominated by coarse grains, and the width of the HAZ increased. However, with the compound physical fields, the weld was mainly composed of equiaxed grains, and the grain size and width of the HAZ decreased. Thus, an increased hardness distribution was also achieved. Moreover, the γ ′ phase exhibited a dispersed distribution and the alloy elements were very uniformly distributed in the γ ′ phase, which helped to prevent the initiation of hot cracking of the weld comprising nickel-based alloys. In addition, the results demonstrated that the generation of additional crystal nuclei and the increase in the cooling rate from the compound physical fields were the main mechanisms for the grain refinement.

The mode splitting induced by electro-optic birefringence in a P—I—N InGaAs/GaAs/AlGaAs vertical-cavity surface-emitting laser (VCSEL) has been studied by polarized electroluminescence (EL) at room temperature. The polarized EL spectra with E ‖ [110] and E ‖ [11̄0] directions, are extracted for different injected currents. The mode splitting of the two orthogonal polarized modes for a VCSEL device is determined, and its value increases linearly with the increasing injected current due to electro-optic birefringence. This article demonstrates that the polarized EL is a powerful tool to study the mode splitting and polarization anisotropy of a VCSEL device. [ABSTRACT FROM AUTHOR]

We theoretically study the influence of the spin—orbit coupling (SOC) on the in-plane optical anisotropy (IPOA) induced by in-plane uniaxial strain and interface asymmetry in (001) GaAs/AlGaAs quantum wells (QWs) with different well width. It is found that the SOC has more significant impact on the IPOA for the transition of the first valence subband of heavy hole to the first conduction band (1H1E) than that of 1L1E. The reason has been discussed. The IPOA of (001) InGaAs/InP QWs has been measured by reflectance difference spectroscopy, whose amplitude is about one order larger than that of GaAs/AlGaAs QWs. The anisotropic interface potential parameters of InGaAs/InP QWs are also determined. The influence of the SOC effect on the IPOA of InGaAs/InP QWs when the QWs are under tensile, compressive or zero biaxial strain are also investigated in theory. Our results demonstrate that the SOC has significant effect on the IPOA especially for semiconductor QWs with small well width, and therefore cannot be ignored. [ABSTRACT FROM AUTHOR]

As an industry accepted storage scheme, hafnium oxide (HfOx) based resistive random access memory (RRAM) should further improve its thermal stability and data retention for practical applications. We therefore fabricated RRAMs with HfOx/ZnO double-layer as the storage medium to study their thermal stability as well as data retention. The HfOx/ZnO double-layer is capable of reversible bipolar switching under ultralow switching current (< 3 μA) with a Schottky emission dominant conduction for the high resistance state and a Poole–Frenkel emission governed conduction for the low resistance state. Compared with a drastically increased switching current at 120 °C for the single HfOx layer RRAM, the HfOx/ZnO double-layer exhibits excellent thermal stability and maintains neglectful fluctuations in switching current at high temperatures (up to 180 °C), which might be attributed to the increased Schottky barrier height to suppress current at high temperatures. Additionally, the HfOx/ZnO double-layer exhibits 10-year data retention @85 °C that is helpful for the practical applications in RRAMs. [ABSTRACT FROM AUTHOR]