Binary Al-Si Alloys Research Articles

Non-destructive determination of silicon in aluminium-silicon alloys by neutron activation analysis with a 227Ac-Be isotope neutron source

A method has been developed for the accurate determination of silicon in binary Al-Si alloys by instrumental neutron activation analysis with the aid of an 227Ac-Be isotope neutron source. Discs, weighing ca. 4 g, are irradiated at the maximum of the fast flux gradient in a rabbit lined internally with two layers of cadmium foil. Each irradiation is followed by an integral mode counting with discriminator baseline setting at 1400 keV. Standards consist of discs from high purity semiconductor silicon and aluminium (99.99%) metal. An iterative calculation procedure yields results with a relative precision from 0.6 to 8.1% for silicon contents between 13.5 and 0.5%. Triplicate analysis requires 21 min.

Hall effect measurements in aluminium alloys

The Hall effect and resistivity have been measured in a series of dilute binary Al-Cu and Al-Si alloys, and a number of ternary Al-Cu-Si alloys. The results have been compared with the predictions of the two band model of Takano (1966), and show that the model is invalid in these cases. There is a simple, nearly linear, relationship between the Hall effect change and the resistivity change in all the alloys and it is concluded that scattering terms dominate the Hall effect changes: in comparison, effects on the Fermi surface due to changes in electron to atom ratio seem negligible. Theory suggests however that normally the resistivity does not appear in expressions for Hall effect, but only the anisotropy of the resistivity. The present results do not permit this anomaly to be resolved.

Wearing behavior of binary Al-Si alloys with cast iron

Sliding test of binary Al-Si alloys containing 22.6% of silicon was conducted with a pearlite cast iron ring in the air with no lubricants.The principal results obtained were as follows:(1) The types of wear were reasonably classified into the following four categories by the observation of surface appearance of the sliding rider (alloy). They were cutting surface wear, black surface wear, deposit surface wear, and Fe2O3 inlaid wear.(2) The wear characteristics were varied as follows, depending upon the silicon content.(a) In the case of cutting surface wear, the rates of wear were increased both in the rider and the ring with the increase of silicon content.(b) The cutting surface wear of the hypo-eutectic alloys was governed by adhesion between the rider and the ring. Therefore, the friction coefficient was decreased with the increase of silicon content. Whereas, the primary silicon crystals in the hyper-eutectic Al-Si alloys substantially scratched the cast iron ring and the friction coefficient of these alloys was increased with the increase of silicon content.(c) Al-Si alloys of high silicon content continued to keep the black surface wear at a considerably high sliding speed.(3) The friction coeffcient of the black surface wear was higher than that of the cutting surface wcar. The surface roughness of the cast iron ring was fairly small in the black surface.(4) The alloy containing 1826% of silicon revealed black spotty surface wear at a high sliding speed.

サブハライド反応によるAlの精製について

Although several reports have been published in regard to an Al extracting method called the “gross process” utilizing the subhalide reaction between Al and AlCl3, very little has been known about the purity of Al produced by this reaction. On selecting the composition of the raw material, quality of the reaction vessel and purpose of the produced Al, it is very important to make clear the contamination route and contents of impurities.In the present work, in order to clarify the contamination route and degree, Fe, Cu and Si in Al produced from Al-Fe, Al-Cu and Al-Si binary alloys have been determined by spectroscopic analysis.As a result, the purification factors for Fe and Cu are about 2×104 and 1×104 respectively, but concentration of Si in the obtained Al is 0.25% constantly regardless of the presence of Si in the raw material.The contamination route of the impurities is discussed from the experimental results and thermodynamic calculations. It has been made clear that the contamination by Fe, Cu and Si arises from the reaction between the oxides of the impurities and AlCl and AlCl3.

Drilling machinability of Al-Si alloys

Drilling machinability test was carried out on Al-Si binary alloys containing 1about 30% of Si. The tool used for the experiments was a drill of the standard type of 5mm in diameter.The time and energy in watt for drilling a predetermined depth was decreased with the increase in Si content; however, there was a maximum at 1013% of Si content.The relation between the drilling time and Si conformed to the fragments of chips. Therefore, the improvement in machinability with increasing Si content would greatly depend upon chip treatments. The machinability was decreased by spherodizing of eutectic Si plate crystals. This tendency was particularly evident in low Si content.In conclusion, it was considered that the drilling machinability was improved by the presence of two phases of proper structres.

Relationship between Si crystallized form and impact strength of Al-Si alloys

The authors were greatly interested in impact properties of binary Al-Si alloys, in which size and distribution of silicon crystals were metallurgically controlled by any way such as sodium modification, phosphor refining, or solution heat treatment at 500°C for 30 240 min. The impact specimens were specially designed that each cast specimen of 55 × 10 mm had an opening on the center of its traverse section instead of a conventional Unotch.The impact strength of Al-Si alloys was greatly increased by heating at 500°C. The fact can be explained by the decrease of stress concentration due to configurational change of eutectic Si from acicular to spherical form during holding. However, the impact strength of hyper-eutectic alloys was not markedly increased even after heat treatment. This fact may be due to the fact that there occurs little changes in configuration of primary crystals of Si during holding. The impact strength as cast alloys was decreased with increasing Si content, while that of heat-treated alloys was not decreased, but was kept constant in the ranges of 5 12%.Small amounts of additional elements also gave slight effects on the impact strength. On addition of Na, the strength tended to be increased for as cast alloys, but it was lower than that of non-treated alloys for heat-treated ones. For alloys containing more than 15% of Si, the addition of Na or P had little effect on the impact strengths of both as cast and heat-treated. A small amount of Na addition caused a marked change in configuration of Si eutectic crystals. The eutectic crystals of as cast alloys were arranged in broomy form in a definite direction. By heat treatment, branches of the crystals were cut into pieces and were distributed in debris structures. The decrease in the impact strength of the specimens treated with Na would be attributed to the change of Si configuration.

気泡噴流法による2Al(l)+AlCl<SUB>3</SUB>(g)=3AlCl(g)反応の平衡恒数およびAl-Si合金中のAl,Si活量の測定

Several reports have been published in regard to the reaction, 2Al(l)+AlCl3(g)=3AlCl(g). These studies were carried out using a surface flow method, in which the reaction could not be equilibrated. Moreover, the equilibrium constant values obtained by these studies widely scatter.In order to equilibrate the reaction and then to obtain a more reliable value of the equilibrium constant, AlCl3 gas was bubbled into molten Al in the present study. By decreasing the hole size of the bubbling tube from 5 mmφ to 1 mmφ, the reaction was equilibrated and the equilibrium constant was directly determined in the temperature range 1000° to 1200°C. The equilibrium constant and standard free energy can be represented by the following equations:(This article is not displayable. Please see full text pdf.) Reactivity between AlCl3 and Al-Si binary alloys in the composition range 0<NSi<0.735 was also investigated. Combining the equilibrium constant with the experimental data on Al-Si alloys, activities of Al and Si were determined at 1200°C. The activity curve is found to be similar in shape to those obtained by Kozuka et al.(10), who determined the values by e.m.f. measurements using a molten chloride electrolyte.