Anisotropic wear of planar-random metal matrix composites with zinc alloy matrix

doi:10.1016/0043-1648(91)90091-8

Wear

Volume 143, Issue 1, 10 March 1991, Pages 149-157

https://doi.org/10.1016/0043-1648(91)90091-8 Get rights and content

Abstract

The effect of varying amounts of δ-alumina fibre on the wear behaviour of an aluminium-zinc alloy with 30% zinc and 2% copper has been investigated. Specimens were produced by infiltrating shaped “Saffil” fibre preforms with molten alloy to produce disc-shaped composite plates with volume fractions of fibre of 10%, 17% and 26%. Metallography showed that the fibres were oriented in a planar random arrangement in the composite plates.

The pin-on-disc technique was used to assess the dry wear resistance and coefficient of friction of the composites over a range of loads and volume fractions of fibres. Testing was carried out with the wear surface set normal and parallel to the surface of the plate in order to determine the effect of predominant fibre orientation on wear behaviour.

The coefficients of friction of the composites were higher than that of the unreinforced matrix alloy, but for both orientations were almost independant of fibre content and load.

In general the wear rate decreased with an increase in volume fraction of fibre and increased with increasing load; however, the fibre orientation had a marked effect on the wear rate and greatly reduced wear occurred when the majority of the short fibres were oriented with their long axes normal to the plane of wear. This effect was particularly marked at the higher loads.

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However, investigations have not been extended to Zn-Al or Al-Zn alloys in this same area of interest. Different testing apparatus are used in determining the wear behaviour of an aluminium-zinc alloys via pin-on-disc (POD), ball-on-disc (BOD), block-on-ring (BOR) and other tribometers [9,13,19]. These techniques are used to assess the dry wear resistance and coefficient of friction of the Zn alloys and composites over a variety of loads and some other varying wear parameters.
The frictional behaviour of Zn-Al alloy was investigated under dry sliding (without lubrication) environment subjected to reciprocating action of ball on disc tribometer. Wrought Zn-Al alloy sample was received as cylindrical rods. The obtained wrought Zn-Al alloy samples were grinded and polished to 0.2 μm mirror-like surface finishing. The hardness was measured from the HV/0.5 indentation tests with a normal load. The phase examination of the Zn-Al alloy material was done by x-ray diffraction (XRD) while the chemical composition was determined by x-ray fluorescence (XRF). A 6.00 mm diameter alumina ball was rubbed against the surface of the Zn-Al alloy samples under increasing normal loads (1, 3, 5 and 10 N) at room temperature and atmospheric humidity. The morphologies of the as received and worn surfaces were examined using high resolution metallurgical optical microscope (OM) and scanning electron microscope (SEM). The CoFs were obtained under dry sliding reciprocating ball on disk tribometer with the InstrumX 7.3.13 version software. The results show that Zn-Al alloy has average hardness of HV/0.5 of 54.4 and average CoFs of 0.1591, 0.413, 0.0739 and 0.4793 under the 1, 3, 5 and 10 N applied loads respectively. Generally, there are slight similarities in the trend CoF – time curves for Zn-Al alloys subjected to small range of frictional loads. There is lower wear resistance due to significant effect of high content of about 98 %Zn in Zn-Al alloy which reduced sliding wear resistance for the Zn-Al alloy as compared with the 1.79 ∼ 0.001 %Zn in the cast A6061 and AlSi alloys previously reported.
Production and anisotropic compressibility of 304 stainless steel fiber/ZA8 zinc alloy interpenetrating phase composites
2017, Journal of Alloys and Compounds
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It is clearly seen that many micropores can be found around the fibers in the IPC at relatively lower pouring temperature (600 °C) and pressure (60 MPa) from Fig. 3a but no pores can be detected in the IPC from Fig. 3b. Kurnaz [23] refers that infiltrating the liquid metal to preforms with different fiber volume needs a range of pressures and increased fiber volume fraction changes the pressure range for infiltration to higher pressures. As the molten metal first infiltrated the larger pores, some additional pressure was required for the further progress of the metal into the narrower channels for the capillarity effect [23,24]. In addition, the molten metal solidifies faster at lower pouring temperature and preheated temperature of mold and preforms, preventing them further infiltrating the remaining pores.
Novel interpenetrating phase composites (IPCs) are produced by infiltrating ZA8 zinc alloy into a variety of possible fibrous preforms via squeeze casting. The preform with spatial network structure is fabricated by compaction following with sintering of 304 stainless steel short fibers. The microstructure and compressive properties of IPCs with different fiber fraction and diameter are investigated. Each constituent phase is found to form a completely interconnected three-dimensional network. The structure of the IPC exhibits anisotropy, i.e., most fibers are parallel to radial section and perpendicular to longitudinal section, which results in differences in hardness and compressive behavior. The hardness of radial section is slightly higher than that of longitudinal section; lower compressive strength and larger fracture strain are presented in radial direction at ambient temperature while higher steady stress and maximum flow stress are performed in hot compression deformation. During compression at room temperature, the increasing fiber volume fraction enhances compressive strength and enlarges elastic stage for both directions. In addition, the IPCs exhibit nonlinear elastic behavior. A finer fiber contributes to improve the hardness and compressive strength. It is also found that with increasing strain during compression, the unreinforced zinc alloy continuously increases its stress without taking fracture, where IPC is compressed to collapse after plastic deformation.
Steel machining chips as reinforcements to improve sliding wear resistance of metal alloys: Study of a model Zn-based alloy system
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This behaviour could tentatively be explained by the formation at this elevated temperature of a local oxide layer (see subsection Section 3.3.2) over the surface which reduces the contact area on the pin surface, and, therefore, reduces friction [25]. ZnO film is well-known as a soft phase and as a lubricant material at high temperature [26]. Fig. 5b shows the variation in wear rate with temperature for the three materials.
Two new steel-reinforced, metal-matrix composites (MMCs), Kirksite+1080 and Kirksite+M2 are developed by adding 25 wt% of AISI 1080/AISI M2 steel machining chips to a zinc-based alloy, Kirksite (4% Al and 3% Cu). The sliding wear resistance of the Zn alloy and the two MMCs, against AISI 52100 steel, is determined under increasing normal load (1–10 N) and temperature (25–150 °C), using a pin-on-disc configuration. The MMCs are found to exhibit superior wear performance under all test conditions. At room temperature, a maximum wear reduction in excess of 70% is obtained for the composites relative to the Zn-alloy at the highest load of 10 N. This reduction is as much as 86% at 150 °C and 1 N for the Kirksite+M2. The wear-reducing ability of the steel reinforcements is generally greater at the more severe contact conditions. The stability of the MMC matrices and recommended limits to the MMC operating temperatures are established using deformation measurements made via dynamic mechanical analysis. The principal wear mechanisms are analysed based on the sliding wear measurements, complemented by optical microscopy and SEM observations, and EDX microanalysis. The results show that the steel chip reinforcements are effective in improving the wear resistance of Zn alloys under severe conditions. Implications for use of low-cost machining chips as reinforcements to create MMCs for improved wear performance, and for recycling/reuse of these chips in advanced structural material systems are discussed.
The influence of porosity and particles content on dry sliding wear of cast in situ Al(Ti)-Al<inf>2</inf>O<inf>3</inf>(TiO<inf>2</inf>) composite
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Cast in situ particle-reinforced aluminum-based composite is characterized by in situ generation of dispersoid particles and also, further value addition due to matrix strengthening caused by alloying. These lightweight composites result in reduced weight when employed in dynamic components, leading thereby to significant fuel economy. Dry sliding behavior of cast in situ Al (Ti)–Al₂O₃(TiO₂) composites synthesized by dispersing titanium dioxide (TiO₂) particles in molten aluminum, has been investigated to explore its potential application in sliding components. Wear tests have been conducted at normal loads of 9.8, 14.7, 19.6, 24.5, 29.4, 34.3 and 39.2 N and a constant sliding speed of 1.05 m/s using a pin-on-disc wear testing machine, under dry sliding conditions. For some specimens of cast in situ composite, wear tests have been also conducted at four different sliding speeds of 0.52, 1.05, 1.57 and 2.10 m/s but at a constant normal load of 34.3 N. The results show that the cumulative volume loss and wear rate of cast in situ composites are significantly lower than those observed in either the cast commercial aluminum or cast unreinforced Al–Ti base alloys, under similar load and sliding conditions. At a given particle content, the wear rate increases with increasing porosity content due to its effect on both the real area of contact and subsurface cracking. The wear rate of cast in situ composites with relatively lower porosity content, decreases with increasing particle content but, in presence of relatively large porosity content, the wear rate decreases only by a little or remain unchanged with increasing particle content. The coefficient of friction of cast in situ composite decreases with increasing porosity content but increases slightly with increasing particle content. In cast in situ composites, porosities were observed to increase the cumulative volume loss and wear rate in all the different types of cast in situ composites. Sometimes, the contributions of the reinforcing particles in enhancing the wear resistance have been obliterated by increased porosity content and therefore, it should be controlled in cast in situ composites. However, a limited amount of porosity could be tolerated in cast in situ composites without impairing its wear resistance significantly. The limitation of wear coefficient as a basis for defining wear resistance has been highlighted and wear rate has been judged as a better parameter for comparing the wear resistance of different cast in situ composites.
The influence of alumina particle dispersion and test parameters on dry sliding wear behaviour of zinc-based alloy
2007, Tribology International
The present investigation deals with dry sliding wear characteristics of a zinc-based alloy (ZA 37) with and without Al₂O₃ particle dispersion over a range of sliding speeds and applied pressures. The matrix alloy has been examined under identical test conditions in order to examine the role played by the second phase alumina particles on wear behaviour. The observed wear behaviour of the samples has been explained in terms of specific characteristics like cracking tendency, lubricating, load bearing and deformability characteristics, and thermal stability of various microconstituents. The nature of predominance of one set of parameters (causing higher wear rate) over the other (producing a reverse effect) was thought to actually control the wear behaviour. Examinations of the characteristic of wear surfaces and subsurface regions also enabled to understand the operating wear mechanism and to substantiate the wear behaviour.
At low sliding speed, significantly lower wear rate of the matrix alloy over that of the composite was noticed. This has been attributed to increased microcracking tendency of the composite than the matrix alloy. Reduced wear rate and higher seizure pressure experienced by the composite over that of the matrix alloy at the higher sliding speeds could be explained to be due to enhanced compatibility of matrix alloy with dispersoid phase and greater thermal stability of the composite in view of the presence of the dispersoid. The maximum temperature rise due to frictional heating has been observed to be low in the case of matrix alloy than composite at low speed while the trend reversed at higher speeds. In general, the wear rate and temperature increased with applied pressure and speed. Seizure pressure reduced with increasing speed while the seizure resistance (pressure) of the matrix alloy was more adversely affected by speed than that of the composite.
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2006, International Journal of Solids and Structures
Anisotropy and heterogeneity of friction and wear can result from anisotropic roughness of engineering surfaces and from anisotropic and heterogeneous microstructures present in many materials (wood, single crystals, ceramics, composites, layer-lattice materials, polymers, biomaterials, monomolecular layers). In sliding surfaces of some materials, kinematics of sliding initiates microstructural and frictional changes. This research deals with advanced constitutive models, which describe evolutions of frictional anisotropy and heterogeneity induced by the sliding kinematics. First-, second- and higher-order constitutive equations of friction are developed with respect to powers of a sliding path curvature. The first-order equation of the friction force has two independent variables: sliding velocity unit vector and its derivative. The second- and higher-order equations are polynomials with respect to odd order tensors composed by the sliding velocity unit vector and the derivative. In the equations, friction tensors of even orders describe anisotropy and inhomogeneity of friction and effects associated with the sliding kinematics. The sliding path curvature generates: (a) an additional resistance to sliding, (b) a constraint force normal to the sliding trajectory. The friction constitutive equations satisfy the axiom of objectivity. A condition of dissipated energy restricts the friction tensors and the radius of curvature. Examples illustrate friction descriptions.

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Anisotropic wear of planar-random metal matrix composites with zinc alloy matrix

Abstract

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Saffil Alumina Fibre: Applications in Metal Matrix Composites

Saffil alumina fibre for metal-matrix composites