Showing papers on "Aluminium alloy published in 1992"
TL;DR: In this article, a pin-on-disc machine was used for sliding wear analysis of A356-SiC composites with 15 and 25 wt.% silicon carbide particles (average size 43 μm).
157 citations
01 May 1992-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this paper, a pin-on-disc machine was used to determine the wear rate of squeeze cast Al alloy (BSS: LM11) matrix composites under varying applied pressure at a sliding spped of 2.68 m s−1 against a rotating EN25 steel disc.
Abstract: Squeeze cast Al alloy (BSS: LM11) matrix composites, each containing 10 vol.% of SiC particles or fibres, have been investigated for their resistance to dry wear under varying applied pressures (1–3 MPa) at a sliding spped of 2.68 m s−1 against a rotating EN25 steel disc. Seizure pressure of the composites as well as the base alloy was determined using a pin-on-disc machine. The alloy containing SiC particles showed less wear rate than the one having SiC fibre dispersion. The base alloy showed maximum rate of wear. Dispersoid-matrix interfacial bonding and shape of the dispersoid were found to play an important role in governing the wear rate of the composites. Scanning electron microscopy examinations indicated relatively finer grooves on the wear surfaces prior to seizure, while seizure led to severely damaged surfaces. Similarly, wear debris generated during wear was thin and flaky prior to seizure, while bulky debris particles were observed during seizure. A few iron machining chips were also found in all the cases. The results obtained have been explained on the basis of wear-induced microstructural changes and deformation, leading to work hardening in the subsurface regions and wear debris.
149 citations
TL;DR: The tribological behavior of aluminium alloy 2014-graphite particle composites has been found to be a function of the volume fraction of graphite particles, and wear resistance can be improved by adding graphite, which causes a corresponding reduction in the coefficient of friction.
126 citations
TL;DR: In this paper, the effects of sintered porosity, volume fraction and particle size of silicon carbide particles (SiC p ) on the abrasive wear resistance of powder metallurgy (P/M) aluminium alloy 6061 matrix composites have been studied.
109 citations
TL;DR: An Al 88 Ni 9 Ce 2 Fe 1 Alloy with ultrahigh tensile fracture strength exceeding 950 MPa in the temperature range from room temperature to 573 K was obtained by rapid solidification in the structural state where the nanoscale fcc-Al particles without internal defects dispersed homogeneously in the amorphous matrix as discussed by the authors.
Abstract: An Al 88 Ni 9 Ce 2 Fe 1 alloy with ultrahigh tensile fracture strength exceeding 950 MPa in the temperature range from room temperature to 573 K was found to be obtained by rapid solidification in the structural state where the nanoscale fcc-Al particles without internal defects disperse homogeneously in the amorphous matrix. The ultimate tensile strength is as high as 1560 MPa at room temperature and 970 MPa at 573 K
85 citations
TL;DR: In this paper, the surface tension and density of liquid binary and ternary aluminium alloys of the systems AlSi-Mg and Al-Zn-mg (Si, Mg and Zn contents less than 19, 8 and 20 wt %, respectively) were measured by means of the maximum bubble pressure method.
Abstract: The surface tension and density of liquid binary and ternary aluminium alloys of the systems Al-Si-Mg and Al-Zn-Mg (Si, Mg and Zn contents less than 19, 8 and 20 wt %, respectively) have been measured by means of the maximum bubble pressure method. A semi-empirical theory, which relates the surface tension to bulk thermodynamic properties, is used to calculate the surface tension of the binary alloys and discuss the experimental data. For the ternary alloys, the present results indicate that in the range of compositions explored here, the properties of the ternaries can be obtained from those of the binaries. Comparison with results previously reported by other authors is made.
85 citations
TL;DR: In this article, a mechanism for the pitting corrosion of Al alloys is proposed based on the literature data and the current results, where the assumption is made that the transport of Cl− ions through defects in the passive film of aluminum and aluminum alloys was not a rate determining step in pitting, and the pit development is controlled by the solubility of the oxidized alloying elements in acid solutions.
71 citations
TL;DR: In this article, a wear mechanism map of aluminium alloys was produced to relate material properties such as hardness and toughness to the wear rate of aluminum alloys under particular load and speed conditions.
71 citations
TL;DR: The basic principles of alloying of aluminum alloys with scandium are: it is desirable to add Scandium together with zirconium in a quantity from 0.1 to 0.3% as discussed by the authors, which strengthens the positive influence on the structure and properties of alloys.
Abstract: The basic principles of alloying of aluminum alloys with scandium are: it is desirable to add scandium to aluminum alloys in a quantity from 0.1 to 0.3% together with zirconium (0.05–0.15%), which strengthens the positive influence of scandium on the structure and properties of alloys; the greatest effect (that is, the positive influence on mechanical properties and other characteristics) from addition of scandium together with zirconium is observed for alloys not containing alloy elements combining scandium in insoluble phases, specifically the Al−Mg, Al−Zn−Mg, and Al−Mg−Li systems; with a limited copper content alloying with scandium together with zirconium of Al−Zn−Mg−Cu and Al−Cu−Li system alloys is possible. At present on the basis of or taking into consideration the principles developed of alloying of aluminum alloys with scandium commercial aluminum alloys based on the Al−Mg−Sc−Sr (01570, 01571, 01523, 01505), Al−Zn−Mg−Sc−Zr (01970, 01975), and Al−Li−Mg−Sc−Zr (10421, 01423) systems have been developed.
63 citations
TL;DR: In this paper, the discovery of very high-strain-rate superplasticity in a mechanically alloyed 15 vol pct SiCp/IN9021 aluminum composite was reported.
Abstract: The discovery of very-high-strain-rate superplasticity in a mechanically alloyed 15 vol pct SiCp/IN9021 aluminum composite is reported. Tensile elongations of more than 500 pct were obtained at strain rates between 5 to 100/s at 823 K. The maximum elongation of 610 pct was recorded at 6/s and 823 K. The potential for high-strain-rate superplasticity in this mechanically alloyed composite is found to be superior to a number of other reinforced aluminum composites. In particular, the superplastic strain rates were many orders of magnitude higher than those for typical superplastic alloys. It is demonstrated that mechanically alloyed composites can exhibit superplasticity in the very high strain rate over 1/s. 13 refs.
61 citations
TL;DR: The various areas involved in the casting process of aluminium alloys are all related with each other and revolve around one primary concern: the hydrogen content present in the molten alloy prior to and during casting and its consequential effect on the porosity and quality of the cast product as mentioned in this paper.
Abstract: The various areas involved in the casting process of aluminium alloys are all interrelated with each other and revolve around one primary concern: the hydrogen content present in the molten alloy prior to and during casting and its consequential effect on the porosity and quality of the cast product. Focusing on this concern, the present article reviews the problems associated with the production of aluminium alloy castings, in particular those areas on which the hydrogen content has a direct bearing. Current procedures in each area are discussed.
TL;DR: In this paper, wear-induced subsurface microstructural changes and material removal mechanisms in squeeze-cast BS LM11 alloy dispersed with 10 vol% SiC were investigated.
Abstract: An attempt has been made to understand wear-induced subsurface microstructural changes and material removal mechanisms in squeeze-cast BS LM11 alloy dispersed with 10 vol% SiC. Particles as well as fibres of SiC were separately dispersed in the alloy matrix to determine the influence of shape of the dispersoid on the abrasion behaviour of the latter. Abrasion tests were conducted on a standard rubber wheel abrasion test apparatus. Silica sand was used as the abrasive medium. Abrasive wear rates of the specimens were found to decrease gradually with the number of test intervals until a steady state value was attained. This was attributed to the protrusion of the reinforcement phase and abrasion-induced work hardening of the matrix in regions close to the abraded surface. The dispersoid/matrix interface as well as the shape of the dispersoid was found to influence the abrasion rate of the composites. A poor dispersoid/matrix interface led to higher rate of abrasion due to pull-out of the dispersoid. On the other hand, good bonding between the dispersoid and the matrix helped the dispersoid phase to be retained by the matrix, offering reduced rate of abrasion.
TL;DR: In this paper, the effects of casting conditions and deformation processing on the mechanical properties of unreinforced A356 aluminum and A356-20 vol pct SiC composite were investigated by tensile properties in these compounds fabricated by either sand casting or squeeze casting techniques.
Abstract: The effects of casting conditions and deformation processing on the mechanical properties of unreinforced A356 aluminum and A356-20 vol pct SiC composite were investigated by tensile properties in these compounds fabricated by either sand casting or squeeze casting techniques followed by hot working to 33, 50, 90, and 95 percent reductions. The evolution of the microstructure and values of tensile properties were evaluated for the cast materials in each of the hot worked conditions. It was found that, while the deformation processing of the sand-cast composite resulted in banding of the Al and SiC particles within the microstructure, such features were not observed in the squeeze-cast microstructure. The tensile strengths of the squeeze cast materials was found to be higher than those of the sand cast materials, for both the unreinforced and composite samples, while increased amounts of deformation were found to improve the ductility of the composite.
TL;DR: In this paper, detailed optical and transmission electron microscopical observations were used to analyse the intrinsic microstructural features of the alloy in the T77 condition, and the fracture behavior was different in the two environments.
Abstract: A study has been made to understand the microstructure, tensile properties and fracture characteristics of aluminium alloy 7150 Detailed optical and transmission electron microscopical observations were used to analyse the intrinsic microstructural features of the alloy in the T77 condition The alloy was deformed to failure over a range of strain rates in environments of 35% sodium chloride solution and laboratory air The environment was found to have little influence on strength of the alloy The strength only marginally increased with an increase in strain rate However, for all strain rates, the ductility of the alloy degraded in the aggressive environment The ratio of strain to failure in sodium chloride solution to that in laboratory air indicates that the alloy is only mildly susceptible to stress corrosion cracking The fracture behaviour was different in the two environments However, in a given environment the fracture behaviour was essentially the same In the aggressive environment fracture was predominantly intergranular while fracture revealed a ductile transgranular failure in laboratory air An attempt is made to discuss the kinetics of the fracture process in terms of competing mechanistic effects involving intrinsic microstructural features, matrix deformation characteristics, environment and strain rate
TL;DR: In this paper, a study was made to understand the low-cycle fatigue and cyclic fracture behavior of the aluminium alloy 2124, which is discontinuously reinforced with varying volume fractions of silicon carbide particulate.
TL;DR: The role of gallium is to bias the surface charge in the direction of activation, and that activation occurs only when sufficient bias has been achieved as mentioned in this paper, and this condition is satisfied by the formation of a number of aluminium complex species.
TL;DR: In this article, the corrosion behavior of squeeze-cast Al alloy (LM11) separately dispersed with 10 vol% SiC fibres and SiC particles was investigated in 3% aqueous NaCl solution by general corrosion as well as potentiodynamic polarization techniques.
Abstract: The corrosion behaviour of squeeze-cast Al alloy (LM11) separately dispersed with 10 vol% SiC fibres and SiC particles was investigated in 3% aqueous NaCl solution by general corrosion as well as potentiodynamic polarization techniques. Erosion-corrosion tests were also performed on the specimens in the solution. The base alloy was also subjected to identical tests to examine the influence of the presence of SiC in the matrix. The base alloy showed a lower corrosion rate than the composites. Furthermore, the alloy containing SiC fibres showed a higher corrosion rate than the one with SiC particle dispersion. Erosioncorrosion tests indicated that the rate of material loss followed a trend similar to that in other corrosion tests. The material loss was significantly higher in the case of erosion-corrosion tests. In addition to pitting and attack at the CuAl2 precipitate-Al interface in the matrix, dispersoid-matrix interfacial attack by the corrosion medium was also observed in the case of composites. On the other hand, erosion-corrosion revealed occasional partial removal of the dispersoid due to the impingement of the electrolyte. The tendency of the dispersoid removal by the impinging electrolyte was predominantly more in the case of the composites dispersed with SiC fibres. Results are explained in terms of the interfacial bonding as well as the shape of the dispersoid.
TL;DR: In this paper, the grain size depends on the temperature-time regime applied: at temperatures higher than 400 °C, enhancing the temperature in a stepwise mode results in grains larger than after isothermal heating.
TL;DR: In this paper, the growth rates of long fatigue cracks have also been measured at different stress ratios using pre-cracked specimens and the distributions of SiC particles and of coarse constituent particles in the matrix have been investigated.
Abstract: Fatigue crack initiation and subsequent short crack growth behaviour of 2014-5wt%SiC aluminium alloy composites has been examined in 4-point bend loading using smooth bar specimens. The growth rates of long fatigue cracks have also been measured at different stress ratios using pre-cracked specimens. The distributions of SiC particles and of coarse constituent particles in the matrix (which arise as a result of the molten-metal processing and relatively slow cooling rate) have been investigated. Preferential crack initiation sites were found to be SiC-matrix interfaces, SiC particles associated with constituent particles and the coarse constituent particles themselves. For microstructurally short cracks the dispersed SiC particles also act as temporary crack arresters. In the long crack growth tests, higher fatigue crack growth rates were obtained than for monolithic alloys. This effect is attributed to the contribution of void formation, due to the decohesion of SiC particles, to the fatigue crack growth process in the composite. Above crack depths of about 200 μm 'short' crack growth rates were in good agreement with the long crack data, showing a Pris exponent, m = 4 in both cases. For the long crack and short crack growth tests little effect of specimen orientation and grain size was observed on fatigue crack growth rates, but, specimen orientation affected the toughness. No effect of stress ratio in the range R = 0.2-0.5 was seen for long crack data in the Paris region.
TL;DR: In this paper, an attempt to review up-to-date knowledge of the conditions of pore formation in cast solidifying metals and alloys is made, and various mechanisms responsible for pore nucleation and growth are summarized, and experimentally evaluated using an unfed type of mould with aluminium alloy castings.
Abstract: Porosity occurs in cast solidifying metals and alloys due to negative pressures generated during solidification contraction, and pressure developed by gases dissolved in the motten metal. Both the above processes may act either together or separately to produce such shrinkage or gas defects (collectively termed pores). They are generally unwanted and constitute a major industrial problem. This paper is an attempt to review up-to-date knowledge of the conditions of pore formation in cast metals and alloys. Various mechanisms responsible for pore nucleation and growth are summarized, and experimentally evaluated using an unfed type of mould with aluminium alloy castings. The observations are in support of a non-nucleation mechanism of pore formation playing a major role in the occurrence of such defects in cast metals. Further, in gas-containing alloy melts the critical amounts of gas required for single and multiple pore nucleation have been determined quantitatively and are listed in the text. The gas contents of the melts were measured using an apparatus based on the “first bubble technique”. It is also experimentally observed that under poor feeding conditions more than one of the non-classical nucleation mechanisms may be functional at the same time for the formation of such defects.
TL;DR: In this paper, the cyclic stress-response characteristics of powder-metallurgy-processed high-purity aluminium alloy 2124 discontinuously reinforced with varying volume fractions of silicon carbide particulates were studied over a range of plastic strains.
TL;DR: In this paper, the detection of high-strain-rate superplasticity in a new aluminum-based crystalline alloy, an as-extruded Al-Ni-Mm (Mm = misch) alloy which was fabricated by warm consolidation of its amorphous powders, was reported.
Abstract: The detection is reported of high-strain-rate superplasticity in a new aluminum-based crystalline alloy, an as-extruded Al-Ni-Mm (Mm = misch) alloy which was fabricated by warm consolidation of its amorphous powders and was developed to be a very fine-grained structure of 70 nm in size, with a very uniform distribution of both Al3Mm and Al3Ni particulates of 70 nm. The maximum elongation of 540 pct was recorded at 0.7 s and 873 K, at which a high m value of 0.5 was obtained. The superplastic strain rate for the Al-Ni-Mm alloy was many orders of magnitude higher than that for typical superplastic alloys. This result shows a new possibility for the development of high strain rate superplasticity in aluminum-based alloys fabricated by warm consolidation of their amorphous powders. 7 refs.
TL;DR: In this article, the influence of pH on the corrosion behavior of two aluminium-lithium-copper-magnesium-zirconium (8090 and 2091) alloys was studied and compared with a standard aircraft alloy, 2014 (Al-4.4% Cu) and 99.9% pure Al. In constant exposure and potentiodynamic polarization studies conducted in 3.5% NaCl solution, all the alloys exhibited high corrosion rates in acidic and alkaline environments, with a minimum in less hostile environments close to neutral pH.
01 Jun 1992-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this article, the role of microstructural parameters on the fracture mechanism of SiC-particle-reinforced aluminium alloy 6061-T6 composites with 5, 10, 20 and 30% volume fraction was investigated.
Abstract: To investigate the role of microstructural parameters on the fracture mechanism, SiC-particle-reinforced aluminium alloy 6061-T6 composites with 5, 10, 20 and 30% volume fraction were tested to measure the fracture toughness on a precracked compact tension specimen. The interparticle spacing of two adjacent particles with the critical size was related to the fracture toughness. The critical particle diameter was experimentally determined from the plastic zone size and the crack-tip-opening displacement using the Hutchinson-Rice-Rosengren solution and the Hahn-Rosenfield model. It has been found that the critical particle diameter decreased as the volume fraction of SiC particles increased.
TL;DR: In this article, the corrosion behavior of sputter-deposited Al-Zr alloys in 1 M HCl solution at 30°C was investigated using electrochemical measurements and XPS analysis.
TL;DR: In this paper, the modified Dugdale model given by Budiansky-Hutchinson and a Coffin-Manson type damage law are used to calculate the cumulative fatigue damage of material elements at the tip of a fatigue crack.
Abstract: The modified Dugdale model given by Budiansky-Hutchinson and a Coffin-Manson type damage law are used to calculate the cumulative fatigue damage of material elements at the tip of a fatigue crack. From this analysis a fatigue crack growth equation is obtained which gives predicted crack growth rates in reasonable agreement with experimental data for two aluminium alloys 7075-T6 and 2024-T81, two titanium alloys Ti-8A1-1Mo-1V and Ti-6A1-6V and a PH13-8Mo stainless steel. Limitations of this new fatigue crack growth model are also discussed.
TL;DR: Amorphous Al88(Y1-xCex)2Ni9Fe1 alloys containing nanoscale fcc-Al particles have been found to exhibit tensile fracture strength (σf) and hardness (HV) higher than those of amorphous single phase alloys with the same compositions, without detriment to good bending ductility.
Abstract: Amorphous Al88(Y1-xCex)2Ni9Fe1 alloys containing nanoscale fcc-Al particles have been found to exhibit tensile fracture strength (σf) and hardness (HV) higher than those of amorphous single phase alloys with the same compositions, without detriment to good bending ductility. The particle size of the fcc-Al phase increases in the range of 3 to 30nm with a decrease in cooling rate. The HV and Young's modulus (E) increase monotonously with increasing volume fraction of the fcc phase (Vf), while the σf shows a maximum in the Vf range of 5 to 26% (e.g., 1560MPa at 25% Vf for Al88Ce2Ni9Fe1).The increase in σf in the Vf range below 26% is presumably due to an enhancement of the resistance to shear deformation caused by the nanoscale fcc particles which have hardness higher than that for the amorphous phase with the same compositions. The highest σf for the Al88Ce2Ni9Fe1 alloy is much higher than that (1320MPa) for the Al88Y2Ni9Fe1 alloy. It is presumably a reason for this difference that the bonding force between Al and Ce atoms is stronger than that between Al and Y.
TL;DR: In this article, the diffusion coefficient of aluminium cations through the amorphous aluminium oxide layer has been determined in the degassing temperature range by using the experimental data of Hayden et al.
Abstract: A study has been performed of the oxidation and degassing processes of aluminium-based alloy powders. Oxidation and hydration of gas-atomized metal powders take place during inflight solidification and cooling to room temperature, during collection and keeping in the powder collection box and during transport and storage before consolidation. Under the atomizing conditions, oxidation cannot be prevented. In contact with humid gases (air) the oxide layer on the powder surface takes up water vapour which is physically or chemically bound. A literature study shows that the oxide layer on atomized aluminium powder is amorphous and has a thickness of 2–10 nm depending on the atomizing conditions. The amount of water in the powder is sufficient to form a completely closed hydroxide layer on the outer surface of the powder. The thickness growth of the oxide layer is governed by cation diffusion. Degassing experiments were carried out by heating canned powders in vacuum. The partial pressures of evolved water vapour and hydrogen were registered as a function of temperature at a constant heating rate. Two different alloy powders were used: the first air atomized and containing 1% magnesium (Al-20Si-3Cu-1Mg-5Fe), and the second (Al-9Fe-2Mo-1Zr) magnesium-free powder, atomized by nitrogen. Much work has been done on degassing, but most of it is directed towards industrial applications. The quantitative theoretical description of the degassing phenomenon is still lacking. A new approach aiming at narrowing this gap is presented by employing Wagner's theory of high temperature oxidation of metals. The diffusion coefficient of aluminium cations through the amorphous aluminium oxide layer has been determined in the degassing temperature range by using the experimental data of Hayden et al. The diffusion coefficient of aluminium cations through the Al2O3 layer has also been evaluated from the degassing experiments. The values obtained directly from the degassing experiments are in reasonable agreement with those derived from the oxidation results. It has been concluded that extrapolation of the results obtained from diffusion experiments at high temperatures in aluminium oxides towards the temperature range of degassing cannot explain the formation of hydrogen during this process, even if the surface diffusion coefficient (much higher than lattice diffusion coefficient) is taken into account.
TL;DR: In this article, the dispersion of longitudinal and transverse waves in metal matrix composites was examined to obtain the dynamic elastic modulus and to evaluate various models for predicting the composite's macroscopic elastic constants from the properties of its constituents.