Si Binary Alloys Research Articles

Mild wear of AlSi binary alloys during unlubricated sliding

The mild wear of AlSi alloys during unlubricated sliding has been investigated. Correlations have been made between the worn surface and debris using optical, electron optical and X-ray techniques. The results indicate that oxidation does not play a significant role and suggest two major mechanisms for the production of wear debris. At low loads, a deformation, compaction and fracture mechanism operates while, at high loads, debris is predominantly formed by a ductile shear mechanism. Both mechanisms operate at intermediate loads.

ChemInform Abstract: The Pitting Corrosion Behavior of Rapidly Solidified Aluminum Alloys

Abstractcontaining Mg, Ti, Mn, Cr, Fe, Ni, Cu, Zn, Zr, Nb and/or Si (binary or ternary alloys) has been investigated in 0.5 N NaCl at 30 °C. Rapid solidification by melt spinning improves the pitting potential by several hundred millivolts except for the alloys containing Mg, Fe or Zn.

A study of aluminium brazes using hot-stage scanning electron microscopy

Hot-stage scanning electron microscopy has been used to study the behaviour of aluminium vacuum brazes. The technique has been employed to observe the surface changes which a braze experiences on heating and to observe the formation of bonds between a braze and a workpiece. 3003 alloy pieces clad with two types of braze were studied: Al-9.3% Si-1.45% Mg alloy and an Al-7.5% Si binary alloy. The magnesium-containing alloy was found to be much more effective in forming joints than the binary alloy, which stemmed from the magnesium-containing alloy's ability to “clean” itself. At the onset of melting the surface of the braze was significantly disrupted by exudation of molten alloy. The exudation was believed to be driven by the volatilization of magnesium and would result in the original oxide layer being broken up, thus making it less effective as a barrier to wetting.

Reaction between Fe–Si Alloys and Liquid Zinc

Seven Fe–Si binary alloys with different silicon concentrations ranging from 0.10 to 2.84 mass% were immersed in a pure zinc bath in the temperature range between 713 K and 873 K for 600 s. The thickness of the alloy layer and the quantities of iron having reacted with zinc were measured, and the structure of the alloy layer was observed. These observations were compared with those of pure iron to offer information about the effect of silicon in galvanizing. Results obtained are as follows:(1) The alloy layer consists of a gamma layer existing next to steel, followed by a delta 1 layer under all the conditions studied. The alloy layer formed next to the delta 1 varies with the silicon concentration of the Fe–Si alloy and the immersion temperature, and four areas are seen in the area map depending on the silicon concentration and the immersion temperature.(2) The reactivity of the Fe–Zn reaction is higher in the region of 0.10 mass%Si and 713 K–733 K, and also in the region of 1–1.15 mass%Si and 773 K–793 K. The former high reactivity is due to the formation of a thicker zeta layer, and the latter is due to the formation of a thicker (delta 1+eta) layer. On the other hand, this reactivity is low in the region of 0.2–0.3 mass%Si, 713 K–793 K, and in the region of 813 K.(3) The Fe–Zn reaction above 833 K does not depend on the silicon concentration of the Fe–Si alloy.

Cyclic Voltammetric Studies of Iron and Cobalt Silicon Alloys (‘Silicides’)

AbstractCyclic voltammetric data are presented for Fe–Si and Co–Si binary alloys in 1M sulphuric acid. Co–Si appears to be less corrosion resistant than Fe–Si.Using a series of controlled potential arrests at both anodic and cathodic limits, the extent of anodic film reduction on the Fe–Si alloys was investigated. It was shown that the anodic film was largely reduced by cathodic holding. The implications for the corrosion rate of the Duriron type anodes used in cathodic protection, when not subjected to load, are considered.

Fatigue crack propagation in iron and two iron binary alloys at low temperatures

Fatigue crack propagation in iron and six FeSi and FeNi binary alloys was studied at temperatures from 123 to 296 K to determine alloy and temperature effects. Crack growth rates were observed to decrease initially with decreasing temperature for all alloys. At some temperature below the ductile-brittle transition temperature the trend reversed, with more prevalent static and/or cyclic cleavage fracture modes enhancing crack growth rates. Fatigue crack propagation exponents corresponding to the enhanced growth rates also increased as the temperature decreased below the ductile-brittle transition temperature. At 100°C below this temperature the exponents were two to four times greater than at 100°C above the transition temperature. The variation of the exponents over this temperature range was substantially less for 1% Ni and 1% Si additions than for 2.5% and 4% additions. A similar trend with alloy addition for the Peierls stress and activation enthalpy, previously observed, indicated that a dislocation dynamics or strain rate sensitivity effect could be involved. A dislocation dynamics model based on cleavage growth steps was derived assuming that dislocations along the rivers of a propagating cleavage crack control cyclic cleavage. The calculated fatigue crack exponents and rates provided good agreement with actual values but showed a weakness in predicting the accelerated growth rates at temperatures well below the ductile-brittle transition temperature.

Wetting of SiC, Si3N4, and Carbon by Si and Binary Si Alloys

The wetting of several new materials for gas turbine engines, e.g. SiC, Si3N4, and C, by liquid Si and binary Si alloys containing Cu, Fe, and B was determined by the sessile drop method. All contact angles measured were < 90°. Hot‐pressed SiC, Si3N4, and Refel SiC are easily wet by Si; wetting is controlled by the balance of interfacial energies. Carbon is wet well by Si, but wetting is controlled by reaction and, in some carbons, by infiltration of Si into C. Additives to Si such as B and Fe can form compounds in reaction zones during wetting at interfacial areas.