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The influences of casting parameters and inclusions on the hydrogen content in 1050 aluminum alloy were studied using optical microscope, scanning electronic microscope and energy dispersive spectroscopy. The results show that with increasing the melt temperature, the environmental humidity and the melt weight, the tendency of hydrogen absorption in 1050 alloy increases. The inclusions in 1050 alloy consist of AlFeSi, Al2O3 and MgO, which always coexist with gas porosity. With increasing the inclusion content, the hydrogen content in Al melt increases. The deep etching method by hot sodium hydroxide employed in this study could evaluate the inclusion content and its distribution more conveniently, quickly and cheaply, is hopeful to be used for site inclusion detection.

Spin transfer torque (STT) driven by a charge current plays a key role in magnetization switching in heavy-metal/ferromagnetic-metal structures. The STT efficiency defined by the ratio between the effective field due to STT and the current density, is required to be improved to reduce energy compulsions in the STT-based spintronic devices. In this work, using the harmonic Hall measurement method, we experimentally studied the STT efficiency in platinum(Pt)/FM structures as a function of the Pt thickness. We found that the STT efficiency strongly depends on the Pt thickness and reaches a maximum value of 4.259 mT/(10 6 A/cm 2 ) for the 1.8-nm-thickness Pt sample. This result indicates that competition between spin Hall effect (SHE) and Rashba effect as well as spin diffusion process across the Pt layer determines the Pt thickness for the maximum STT efficiency. We demonstrated the role played by the spin diffusion besides the spin current generation mechanisms in improvement of the STT efficiency, which is helpful in designing STT-based devices.