Influence of Bifilm Defects Generated during Mould Filling on the Tensile Properties of Al–Si–Mg Cast Alloys

Entrapped double oxide film defects are known to be the most detrimental defects during the casting of aluminium alloys. In addition, hydrogen dissolved in the aluminium melt was suggested to pass into the defects to expand them and cause hydrogen porosity. In this work, the effect of two important casting parameters (the filtration and hydrogen content) on the properties of Al–7 Si–0.3 Mg alloy castings was studied using a full factorial design of experiments approach. Casting properties such as the Weibull modulus and position parameter of the elongation and the tensile strength were considered as response parameters. The results suggested that adopting 10 PPI filters in the gating system resulted in a considerable boost of the Weibull moduli of the tensile strength and elongation due to the enhanced mould filling conditions that minimised the possibility of oxide film entrainment. In addition, the results showed that reducing the hydrogen content in the castings samples from 0.257 to 0.132 cm3/100 g Al was associated with a noticeable decrease in the size of bifilm defects with a corresponding improvement in the mechanical properties. Such significant effect of the process parameters studied on the casting properties suggests that the more careful and quiescent mould filling practice and the lower the hydrogen level of the casting, the higher the quality and reliability of the castings produced.

Progress in Mo/W-based electrocatalysts for nitrogen reduction to ammonia under ambient conditions

Ammonia (NH3), possessing high hydrogen content and energy density, has been widely employed as fertilizers and value-added chemicals in green energy carriers and fuels. However, the current NH3 synthesis largely...

Analysis on Influence of Hydrogen Content Exceeding Standard in GaAs Device

Aiming at the problem of hydrogen content exceeding the standard in GaAs device, the influence mechanism of hydrogen content exceeding the standard on the device is analyzed, the failure model of hydrogen content exceeding the standard in GaAs device in engineering is given, the source of hydrogen is analyzed, and the protective measures of hydrogen content exceeding the standard are given. It is of certain guiding significance for future engineering application.

The enhanced thermal stability and reduced hygroscopicity of aluminum hydride coated with Vinyltrimethoxysilane

Alpha-aluminum hydride (α-AlH3) is an excellent high-energy additive for solid propellants because of its high hydrogen content (10.8 wt%) and energy density, low decomposition temperature, and good combustion performance. However,...

Assessment of Interchangeability of Fuels Used in the Process of Heat Production and Comparison of Their Selected Characteristics: A Case Study

Exchangeability means the possibility of the fuel changing, with conservation of the required energy and environmental criteria. The assessment of fuel exchangeability should be realized by a suitable method, which must reliably present the possibility of the exchangeability of fuels, or reject it. In the presented paper, research on the exchangeability of solid fuels in the field of heating production is surveyed by the case study. Based on the available published knowledge from previous studies on fuel exchangeability, the statistical method was chosen for evaluation. The application of this method is useful. For example, by evaluating the exchangeability of natural gas, the manuscript will describe its application for the field of solid fuels in heat production. The research evaluated and analyzed the sample of 12 fuels. For each fuel sample, 35 gas attributes were measured, which were classified into separate flue gas attribute groups: ash content, combustion heat, heating capacity, sulfur content, combustible content, water content, emission factor, carbon content, hydrogen content, and oxygen content. Attributes of flues were evaluated and grouped according to the fuel properties—ash content and combustion heat, sulphur content, water content, emission factor, carbon content, hydrogen content, nitrogen content, oxygen content, and combustible content.

Hydrogen Absorption during Case Hardening of Steels EN20MnCr5 (SAE5120) and EN18CrNiMo7-6 (SAE4820)

Damages to case-hardened components are often associated with the phenomenon of hydrogen embrittlement due to their specific fracture pattern. In the present work, the effects of the case hardening process on the hydrogen content in the material were investigated and the effects of hydrogen on the mechanical properties were examined. In order to determine not only the influence of the heat treatment process but also the influence of the material, the case-hardening steels EN20MnCr5 (SAE5120) and EN18CrNiMo7-6 (SAE4820) with different degrees of purity were investigated. From the results it can be deduced that the sulphidic and oxidic inclusions have no significant influence on the hydrogen content. When checking the mechanical properties, it was shown in the incremental step loading technique according to ASTM F1624 that a purely case-hardened condition only has a slight tendency to hydrogen embrittlement. However, if the material is additionally loaded with hydrogen, the material fails significantly below the maximum expected load in the incremental step loading test, which is to be interpreted as a clear indication of failure due to hydrogen embrittlement. However, the fracture patterns of these two states do not show any significant differences. Therefore, it does not seem possible to attribute damage to a case-hardened component to hydrogen embrittlement on the basis of the fracture pattern alone.

Effect of Hydrogen, Hydride Orientation and Temperature on Low-Cycle Fatigue Resistance of Zr-1%Nb Fuel Rod Claddings

Low-cycle fatigue testing was conducted on annular samples with an outer diameter of 9.13 mm, a wall thickness of 0.68 mm and a width of 2.7 mm, namely: non-hydrogenated samples (cut out of standard Zr‑1%Nb cladding tubes); hydrogenated samples with a hydrogen concentration of 50 ... 400 ppm; samples cut out from hydrogenated dummy claddings after hydride reorientation tests performed according to various test modes. The tests were conducted at the temperatures of 25, 180, 350, 400 and 450 °С. The results obtained demonstrate that with increasing the hydrogen content in Zr-1%Nb alloy claddings the fatigue life increases.