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Based on the time domain analytical expression of the pulsed eddy current field of a ferromagnetic flat plate, the least square parameter inversion problem between the measured value of the time-domain induced voltage and the theoretical value is established. Set the conductivity of the tested component as a fixed constant and then compare the inversion results of the wall thickness of the two test points to obtain the relative change of the wall thickness between the two test points. The rectangular groove defect is machined on the steel plate, and the experiment verifies that the relative wall thickness detection method in this paper can eliminate the influence of the set value of component conductivity. When the area of the corrosion area is larger than the area of the foot of the probe, the residual wall thickness of the corrosion area can be accurately scanned, and the edge of the corrosion area has good recognition ability. When the area of the thinning area is smaller than the area of the probe foot, the thinning degree of local corrosion defects will be underestimated. The pulsed eddy current method is used to detect the relative wall thickness of ferromagnetic components without contacting with the tested components. The detection results are intuitive and the repeatability is high. It can be used for nondestructive testing and evaluation of the corrosion thinning of the wall thickness of ferromagnetic components with coating in industry. [ABSTRACT FROM AUTHOR]

Abstract: Complex hydrides and Metal–N–H-based materials have attracted considerable attention due to their high hydrogen content. In this paper, a novel amide–hydride combined system was prepared by ball milling a mixture of Na2LiAlH6–Mg(NH2)2 in a molar ratio of 1:1.5. The hydrogen storage performances of the Na2LiAlH6–1.5Mg(NH2)2 system were systematically investigated by a series of dehydrogenation/hydrogenation evaluation and structural analyses. It was found that a total of ∼5.08wt% of hydrogen, equivalent to 8.65moles of H atoms, was desorbed from the Na2LiAlH6–1.5Mg(NH2)2 combined system. In-depth investigations revealed that the variable milling treatments resulted in the different dehydrogenation reaction pathways due to the combination of Al and N caused by the energetic milling. Hydrogen uptake experiment indicated that only ∼4moles of H atoms could be reversibly stored in the Na2LiAlH6–1.5Mg(NH2)2 system perhaps due to the formation of AlN and Mg3N2 after dehydrogenation. [ABSTRACT FROM AUTHOR]

An integral manufacturing process with hot drawing and cold flow forming was proposed for large-diameter seamless steel gas cylinders. The main purpose of this study was to find out the effects of the manufacturing process on the microstructure and mechanical properties of gas cylinders made of 34CrMo4 steel. Two preformed cylinders were produced by hot drawing. One cylinder was then further manufactured by cold flow forming. The experiments were carried out using three types of material sample, namely, base material (BM), hot drawing cylinder (HD), and cold flow-formed cylinder (CF). Tensile and impact tests were performed to examine the mechanical properties of the cylinders in longitudinal and transverse directions. Microstructure evolution was analyzed by scanning electron microscopy (SEM) and electron backscatter diffraction (EBSD) to reveal the relation between the mechanical properties and the microstructure of the material. It is found that the mechanical properties of the 34CrMo4 steel gas cylinders were significantly improved after hot drawing and flow forming plus a designed heat treatment, compared with the base material. The observations of microstructure features such as grain size, subgrain boundaries, and residual strain support the increase in mechanical properties due to the proposed manufacturing process. [ABSTRACT FROM AUTHOR]