Determination of the content of impurity elements in a sample of high purity India by the method of radiochemical neutron activation analysis

The present article is devoted to the development of a method for neutron activation analysis of a microimpurity composition of high-purity indium with the radiochemical separation of indium radionuclides from radionuclides of the determined elements by extraction chromatography in the system tributyl phosphate (TBP) - solutions of hydrobromic acid (HBr). Neutron activation analysis (NAA) has a special place among the physical methods for determining the trace composition of high-purity substances. Low detection limits, the possibility of simultaneous determination of a large number of impurity elements from one sample, no correction for the control experiment, the possibility of using inactive carriers in separating traces of radionuclides of impurity elements from matrix elements ensured the widespread use of NAA in the analysis of highly pure substances. The developed technique allows separating matrix radionuclides from radionuclides of impurity elements with high efficiency and determination of 28 impurity elements in high-purity indium with detection limits of 0.7 ppm to 0.05 ppb.

Research on Microstructure and Growth Mechanism of Different Primary Silicon in Hypereutectic Aluminum Alloy

The as-cast microstructure of a typical hypereutectic Al-25Si alloy was studied, and the growth mechanism of different primary silicon phases was analyzed. The results show that the as-cast microstructure phase composition of the alloy is mainly primary silicon and eutectic silicon. Primary silicon is mainly petal-like, massive and other complex polyhedrons, and there are a lot of cavities, cracks and other defects in the interior and boundary; Eutectic silicon is coarse and long needle-like, and the distribution is relatively messy, which seriously deteriorates the mechanical properties and cutting performance, and hinders the further application of the alloy in the field of lightweight pistons. Petal-shaped primary silicon is grown by combining five tetrahedral crystal nuclei in the melt into a decahedron, while bulk primary silicon is mainly caused by the unbalanced aggregation of impurity elements. And these two types of silicon phase growth methods are related to the twin groove growth mechanism, which is the result of a combination of multiple mechanisms.

Precipitation Hardening at Elevated Temperatures above 400 °C and Subsequent Natural Age Hardening of Commercial Al–Si–Cu Alloy

The precipitation of intermetallic phases and the associated hardening by artificial aging treatments at elevated temperatures above 400 °C were systematically investigated in the commercially available AC2B alloy with a nominal composition of Al–6Si–3Cu (mass%). The natural age hardening of the artificially aged samples at various temperatures was also examined. A slight increase in hardness (approximately 5 HV) of the AC2B alloy was observed at an elevated temperature of 480 °C. The hardness change is attributed to the precipitation of metastable phases associated with the α-Al15(Fe, Mn)3Si2 phase containing a large amount of impurity elements (Fe and Mn). At a lower temperature of 400 °C, a slight artificial-age hardening appeared. Subsequently, the hardness decreased moderately. This phenomenon was attributed to the precipitation of stable θ-Al2Cu and Q-Al4Cu2Mg8Si6 phases and their coarsening after a long duration. The precipitation sequence was rationalized by thermodynamic calculations for the Al–Si–Cu–Fe–Mn–Mg system. The natural age-hardening behavior significantly varied depending on the prior artificial aging temperatures ranging from 400 °C to 500 °C. The natural age-hardening was found to strongly depend on the solute contents of Cu and Si in the Al matrix. This study provides fundamental insights into controlling the strength level of commercial Al–Si–Cu cast alloys with impurity elements using the cooling process after solution treatment at elevated temperatures above 400 °C.

Principles of Metal Refining and Recycling

Covers the field of recycling and refining of metals. An important point the book stresses is that the principles are the same in the treatment of various different metals. The book answerd why it is important to have a clean and properly alloyed metal from recycling and refined metal? The text covers basic thermodynamics, physical and transport properties, mixing, mass transfer and numerical models. Further it identifies problems and described methods for removal of dissolved impurity elements, particles and inclusions, also during solidification. And lastly applications remelting and addition of alloys, recycling and challenges and specific processes for each metal are included. The book is self-contained.

THE REFINING OF TITANIUM BY CRUCIBLELESS ZONE MELTING METHOD

The physical substantiation of titanium refining by crucibleless electron beam zone melting (ZM) method in vacuum was presented. Calculations of the equilibrium, limiting and effective distribution coefficients for impurity elements in the base metal were carried out. The refining of titanium was studied experimentally, and samples with a purity of 99.92 wt.% were received. The total content of impurities was reduced by a factor of 1.5 (from 0.12 to 0.08 wt.%). The concentration of interstitial impurities was significantly reduced (oxygen – by 1.3; carbon – by 2; nitrogen – by 2.5 times). The structure and microhardness were investigated.