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Showing papers on "Aluminium alloy published in 1988"


Journal ArticleDOI
TL;DR: In this paper, a new Al-based amorphous alloys with high strength and good ductility were produced in an Al-Y-Ni system by liquid quenching.
Abstract: New Al-based amorphous alloys with high strength and good ductility were produced in an Al-Y-Ni system by liquid quenching. The tensile fracture strength ( σf) and Vickers hardness reach 1140 MPa and 300 DPN for Al87Y8Ni5. The specific strength defined by the ratio of σf to density is as high as 38, being much higher than that for conventional alloy steels. The high-strength Al-base amorphous alloys are expected to attract strong attention as a new type of high-strength material with low density.

310 citations


Journal ArticleDOI
TL;DR: In this paper, the first amorphization for the Al-M binary alloys was reported, which is important for subsequent development of Al-based amorphous alloys with high specific strength.
Abstract: New amorphous alloys in Al-M (M=Y, La or Ce) binary systems have been formed in the compositional ranges of 9 to 13 at% Y and 7 to 10 at% La or Ce by liquid quenching. Crystallization temperature, Vickers hardness and electrical resistivity at 293 K of the binary amorphous alloys increase with an increase of Y, La or Ce content from 437 to 516 K, 116 to 216 DPN and 54 to 93 µΩcm, respectively. The first amorphization for the Al-M binary alloys is important for subsequent development of Al-based amorphous alloys with high specific strength.

152 citations


Journal ArticleDOI
TL;DR: In this paper, the manufacturing processes for metal matrix composites, in particular those based upon liquid metal technology, e.g., squeeze casting and spray forming, are described. And an analysis of how matrix alloy selection may influence tensile and fracture behaviour of short fibre and particle reinforced composites is attempted.
Abstract: Metal matrix composites have been available in certain forms for at least two decades, e.g. boron fibre reinforced aluminium and various dispersed phase alloys and cermets. Recently, a range of alumina and silicon carbide fibres, whiskers, and particles with diameters <20 μm have become available. The possibilities of incorporating these materials into metals to improve stiffness, wear resistance, and elevated temperature strength without incurring weight penalties have attracted the attention of design engineers in the aerospace and automobile industries. The aim of the present paper is to outline the manufacturing processes for such composites, in particular those based upon liquid metal technology, e.g. squeeze casting and spray forming. Some of the mechanical and physical properties which have been determined for these materials are described. An analysis of how matrix alloy selection may influence tensile and fracture behaviour of short fibre and particle reinforced composites is attempted.MS...

138 citations


Journal ArticleDOI
TL;DR: In this article, the effect of Nd:YAG laser welding aluminum alloys 6061, 5456, and 5086 was studied from a perspective of alloying element vaporization, hot cracking susceptibility, and resultant mechanical properties.
Abstract: The effect of Nd:YAG laser welding aluminum alloys 6061, 5456, and 5086 was studied from a perspective of alloying element vaporization, hot cracking susceptibility, and resultant mechanical properties. Both continuous wave and pulsed Nd.YAG laser welds were investigated. It was found that Mg was vaporized during welding, the extent of which was a function of the weld travel speed. Calculations based upon evaporation theory, and assuming a regular solution model, resulted in an estimation of weld pool surface temperatures from 1080 to 1970 K for the continuous wave welds. Pulsed Nd:YAG laser welds were observed to be extremely susceptible to weld metal hot cracking whereas continuous wave Nd:YAG laser welds were crack-free. The hardness of 6061 welds was affected by the Mg vaporization such that base metal strengths could not be achieved by subsequent re-heat treatment to the T6 condition. This loss in hardness was attributed to a reduced ability of the alloy to precipitation harden due to a lower Mg concentration. In the cases of 5456 and 5086, when samples containing welds were processed to the O condition, the weld metal had reduced hardness relative to the base metal. This loss of hardness was also attributed to the loss of Mg in these welds, resulting in reduced solid solution strengthening.

110 citations


Journal ArticleDOI
TL;DR: In this paper, surface finish data were generated for aluminium alloy 390, ductile cast iron, medium carbon leaded steel 10L45, and medium carbon alloy steel 4130 for a wide range of machining conditions defined by cutting speed, feed and tool nose radius.
Abstract: Surface finish data were generated for aluminium alloy 390, ductile cast iron, medium carbon leaded steel 10L45, medium carbon alloy steel 4130, and inconel 718 for a wide range of machining conditions defined by cutting speed, feed and tool nose radius. These data were used to develop surface finish prediction models, as a function of cutting speed, feed, and tool nose radius, for each individual metal. A general purpose surface finish prediction model is also proposed for ductile cast iron, medium carbon leaded steel, and alloy steel. Statistical analysis of experimental data indicated that surface finish is strongly influenced by the type of metal, speed and feed of cut, and tool nose radius. While the effects of feed and tool nose radius on surface finish were generally consistent for all materials, the effect of cutting speed was not. The surface finish improved with speed for ductile cast iron, medium carbon leaded steel, medium carbon alloy steel, and aluminium alloy, but it deteriorated with speed...

109 citations


Journal ArticleDOI
Joong Keun Park1
TL;DR: In this paper, the influence of retrogression and reaging (RRA) treatments on high strength aluminium alloy 7075 was studied using hardness and tensile testing and by measuring the stress corrosion crack growth rate using doublecantilever-beam specimens.
Abstract: The influence of retrogression and reaging (RRA) treatments on high strength aluminium alloy 7075 was studied using hardness and tensile testing and by measuring the stress corrosion crack growth rate using double-cantilever-beam specimens. Transmission electron microscopy was used to study the microstructures at both the matrix and the grain boundary. The RRA treatments result in a significant improvement of the stress corrosion resistance of aluminium alloy 7075-T651 without sacrificing its maximum strength. The crack velocity decreases to a level comparable with that of the T73 structure as a result of the optimum RRA treatments. The initial strength decrease during the retrogression treatment is mainly due to a dissolution of small η′ particles. The coarsening of grain boundary precipitates occurs during the retrogression treatment. The steady state crack velocity decreases logarithmically with increase in the volume fraction of grain boundary precipitates.

99 citations


Journal ArticleDOI
TL;DR: In this article, the free energy curves of the amorphous and bcc phases were calculated from the phase diagram and additional thermodynamic data, and the formation of the different phases can be understood by considering the free energies of different phases.
Abstract: Nb‐Al alloys have been prepared by mechanical alloying of elemental crystalline powders and investigated with x‐ray diffraction and transmission electron microscopy. Crystalline equilibrium phases form for Al‐rich alloys. Amorphous phase formation is observed for the Nb50Al50 composition. Mechanically alloyed powders with more than 70 at. % Nb exhibit the metastable bcc (A2) solid solution which transforms after thermal annealing into the A15 phase. Formation of the different phases can be understood by considering the free‐energy curves of the amorphous and bcc phases as calculated from the phase diagram and additional thermodynamic data.

82 citations


Journal ArticleDOI
TL;DR: In this paper, the mechanical properties (i.e., tensile fracture strength and Young's modulus) of eight different alloys of a new class of metallic glasses containing up to 90% aluminum are reported along with crystallization temperatures of these alloys.
Abstract: The mechanical properties (i.e., tensile fracture strength and Young’s modulus) of eight different alloys of a new class of metallic glasses containing up to 90 at. % aluminum are reported along with crystallization temperatures of these alloys. The Al90Fe5Ce5 material has a tensile fracture strength of 940 MPa (1 MPa=145 psi), while two others (Al87Fe8.7Gd4.3 and Al87Ni8.7Y4.3) exceed 800 MPa. Young’s modulus measurements for three of these exceed 60 GPa with a high value of 66 GPa for the Al90Fe5Ce5 glass. These unusually high strengths of the aluminum glasses can be of significant importance in obtaining high‐strength, low‐density materials.

82 citations


Journal ArticleDOI
TL;DR: In this paper, the effect of aluminium filler metal composition on the formation of AI-Ti intermetallic compounds was investigated in brazed aluminium-to-titanium (Al/Ti) joints and titanium-totitanium-Ti/Ti joints.
Abstract: The effect of aluminium filler metal composition on the formation of AI-Ti intermetallic compounds was investigated in brazed aluminium-to-titanium (Al/Ti) joints and titanium-totitanium (Ti/Ti) joints. The clearance filling ability was also studied. In Ti/Ti joints, the thickness of the intermetallic compound layer was strongly dependent on the aluminium filler metal composition, whereas the clearance filling ability was independent of the composition. The maximum intermetallic compound layer thickness was observed in 99.99% highly pure aluminium filler metal; therefore all additional elements reduced the layer thickness. Above all, the addition of 0.8% Si greatly reduced the thickness. After brazing at 680° C for 3 min, the intermetallic compound formed by Al-0 to 0.8% Si filler metal was found to be of type Al3Ti. Other compounds, of types Ti9Al23 and Ti7Al5Si12, were also found in joints brazed by Al-3 to 10% Si filler metals. AI-0.8% Si filler metals maintained a higher joint strength than pure aluminium filler metal under brazing conditions of high temperature and long heating time. In Al/Ti joints, AI-Cu-Sn and AI-Cu-Ag filler metal mainly formed Al3Ti, and Al-10Si-Mg filler metal mainly formed Ti7Al5Si12 at the brazed interface of the titanium side after brazing at 600 to 620° C.

74 citations


Journal ArticleDOI
Akihisa Inoue1, Y. Bizen1, Hisamichi Kimura1, T. Masumoto1, M. Sakamoto 
TL;DR: An amorphous single phase was found to be formed in wide compositional ranges in rapidly solidified Al-Si-transition metal (M) and Al-Ge-M alloys as discussed by the authors.
Abstract: An amorphous single phase was found to be formed in wide compositional ranges in rapidly solidified Al-Si-transition metal (M) and Al-Ge-M alloys. The compositional ranges are in the range from 12 to 53 at. % Si or Ge and 8 to 23% M and Al-Si-Co and Al-Ge-Fe alloys have the widest glass-formation ranges. Because the interaction between aluminium and silicon or germanium atoms is thought to be repulsive from the immiscible equilibrium phase diagrams, the glass formation is probably due to an attractive interaction of M-Si (or Ge) and Al-M pairs. Hardness, H v, and crystallization temperature, T x, increase with increasing M content and the highest values reach 1120 DPN and 715 K, while the change with silicon or germanium content is much smaller for H v and is hardly seen for T x. Additionally, the H v and T x have maximum values for Al-Si (or Ge)-M (M=Cr, Mn or Fe), decrease with the decrease and increase in the group number of M element and are the lowest for Al-Si (or Ge)-Ni alloys. The compositional dependence is interpreted under the assumption that T x and H v of the aluminium-based amorphous alloys are mainly dominated by the attractive interaction of M-(Si or Ge) and Al-M pairs. Room-temperature resistivity, ϱ RT, increases in the range of 220 to 1940 μΩ cm with increasing silicon or germanium and M contents. The change in ϱ RT with the group number of M elements shows a maximum phenomenon for manganese. It has thus been clarified that the characteristics of the Al-Si-M and Al-Ge-M amorphous alloys have the different compositional dependence as compared with those for conventional metalmetalloid amorphous alloys, probably because of the unusual interaction among the constituent elements.

68 citations


Journal ArticleDOI
TL;DR: In this paper, an analysis of the compressive test results is given based on the mixture rule modified to apply for discontinuous randomly oriented fiber composites. But, it is shown that agreement between predictions and experimental results can only be obtained by considering the increase of the strength of the matrix as a result of the presence of the fibres.
Abstract: Composites made with Al–7 wt-%Si alloys and discontinuous Nicalon SiC fibres were prepared by compocasting followed by squeeze casting. This technique gives rise to macroscopically homogeneous materials with, however, some segregation of the fibres in the eutectic phase, especially for the lowest volume fractions. The SiC fibres appreciably improve wear resistance, hardness, and compressive strength of the matrix, both in the as cast and heat treated conditions. An analysis of the compressive test results is given based on the mixture rule modified to apply for discontinuous randomly oriented fibre composites. However, it is shown that agreement between predictions and experimental results can only be obtained by considering the increase of the strength of the matrix as a result of the presence of the fibres. This increase is discussed in terms of structural changes and residual stresses created during cooling resulting from the difference in the coefficients of thermal expansion of the components...

Journal ArticleDOI
TL;DR: In this article, the Bauschinger effect has been used to measure internal stress and shows that the tensile behavior of these materials is determined by the development of these stresses due to the plastic flow of the matrix, differences in elastic constants of the two phases and residual thermal stresses developed during fabrication.

Journal ArticleDOI
TL;DR: In this article, the formation and thermal stability of aluminum-rich metallic glasses was studied. But the formability of these new glasses has been found to be unusual. And the results showed that many of them have tensile strengths over 800 MPa, greatly exceeding the strongest commercial aluminum alloys.

Journal ArticleDOI
TL;DR: In this article, the mechanical properties of steel wire-reinforced aluminium matrix composites were investigated and it was found that their tensile strength was somewhat lower than that predicted by the rule-of-mixtures; failure occurred predominantly by fibre pull-out.

Journal ArticleDOI
TL;DR: In this article, the effect of anisotropy of the fiber thermal expansion on thermal stress was examined by extending a thick-walled cylinder model for graphite/aluminium composites.

Journal ArticleDOI
TL;DR: The neutron diffraction technique for measuring residual stresses non-destructively in an aluminium alloy weld has been examined in this article, and the results showed that the technique can be used to determine residual stresses in an aluminum alloy weld.
Abstract: The neutron diffraction technique for measuring residual stresses non-destructively in an aluminium alloy weld has been examined. Calibration experiments have been performed to determine th...

Journal ArticleDOI
TL;DR: In this paper, a metallographic study of diffusion bonds between aluminium and copper has been made in order to further understand the mechanism of bond formation for joints between dissimilar metals that form intermediate phases or intermetallic compounds.
Abstract: A metallographic study of diffusion bonds between aluminium and copper has been made in order to further understanding of the mechanism of bond formation for joints between dissimilar metals that form intermediate phases or intermetallic compounds. A three-stage mechanistic model based upon sintering principles has been proposed to explain this kind of diffusion joint.

Journal ArticleDOI
TL;DR: In this paper, the microstructure of a cast Al-Si alloy-graphite particle composite was examined using optical and analytical scanning electron microscopy, and it was shown that the reduction in machining forces with increasing graphite content is due mostly to a decrease in the shear flow stress rather than to lower chip-rake-face friction.
Abstract: The microstructure of a cast Al---Si alloy-graphite particle composite is examined using optical and analytical scanning electron microscopy. Specimens containing different percentages of graphite were machined by orthogonal planning with 25° and 45° rake angle tools at both 6.5 and 13.2 m min−1. The machining forces are reported and the chip-rake-face friction coefficients and shear flow stresses are calculated. It is shown that the reduction in machining forces with increasing graphite content is due mostly to a decrease in the shear flow stress rather than to lower chip-rake-face friction. Both the polished and the machined surfaces of the composite are rougher than those of the simple alloy, apparently owing to the greater porosity, the tearing out of graphite particles, or the opening of cracks at the graphite particles in the wake of the tool.

Journal ArticleDOI
TL;DR: In this paper, the machinability of two classes of high-temperature composites (SiC whisker/2124 aluminium and SiC whiskers/Al2O3) with an abrasive waterjet (AWJ) was investigated.
Abstract: The machinability of two classes of high-temperature composites (SiC whisker/2124 aluminium and SiC whisker/Al2O3) with an abrasive waterjet (AWJ) was investigated. The as-machined surfaces of the composites were characterized by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), and profilometry to determine the surface finish. Microhardness measurements were also performed on the as-machined metal matrix composites. AWJ appears to be a quite promising machining method due to its fast speed and economical operation. It gives relatively smooth surfaces coupled with minimum subsurface microstructural damage.

Journal ArticleDOI
TL;DR: The experimental results for some 80 aluminium alloy and mild steel double-shear specimens were reported in this paper, where they were subjected to impact loads in a drop hammer rig and, from the experimental results, a number of empirical relations were obtained which relate the deformation of a specimen to the impact energy of a drop mass.

Journal ArticleDOI
TL;DR: In this article, the effect of surface pretreatment and "oxide penetration" by the adhesive matrix on durability of aluminium-bonded surfaces is investigated. But the results show little damage to the adhesive or adherend.
Abstract: The interface in aluminium bonded structures can be revealed by ultramicrotomy and subsequently studied by transmission electron microscopy. By these means, the more usual surface pretreatments encountered, have been characterised in depth. A similar examination has been effected following exposure of bonded joints (floating roller peel specimens) to 85% relative humidity at 70°C. Although a drop in peel performance is noted over the exposure time, interfacial examination reveals little damage to the adhesive or adherend. Possible mechanisms for bond strength reduction are discussed: subtle undermining of the alumina film and disruption of physico-chemical bonds across the interface. Both are initiated by moisture reaching the alumina film, either passing along the interface itself or travelling through the adhesive matrix. Also considered are the effects of surface pretreatment and “oxide” penetration, by the adhesive, on durability. The effect of priming the adherend surface prior to bonding, u...

Journal ArticleDOI
TL;DR: In this paper, the relationship between microstructure and properties in rapidly solidified NiAl alloys whose melting point is of the order of 1900 K was investigated and it was concluded that NiAl's strength can be significantly increased through dispersoid additions without sacrifice of high temperature ductility.
Abstract: Initial experimental results are presented concerning the relationship between microstructure and properties in rapidly solidified NiAl alloys whose melting point is of the order of 1900 K. When the dispersoid content of NiAl alloys is increased, the dispersoids begin to populate the grain boundaries, rendering them weak, so that failure must propagate intergranularly. It is concluded that NiAl alloys' strength can be significantly increased through dispersoid additions without sacrifice of high temperature ductility.

Journal ArticleDOI
TL;DR: In this article, a 20 kHz ultrasonic vibrator was used on a copper-manganese-aluminium alloy used for marine propellers by means of a 20 Hz vibrator and the effect of the ultrasonic probe on free corrosion potential was investigated.
Abstract: Cavitation corrosion in natural sea water has been induced on a copper–manganese–aluminium alloy used for marine propellers by means of a 20 kHz ultrasonic vibrator. The stirring effect of the ultrasonic probe on the free corrosion potential was investigated. A synergistic effect of cavitation and corrosion was found and attributed to microcracking and grain boundary corrosion which weakens the material and allows σ grains to become detached. The material was found to contain an active, brittle phase which is sensitive to both cavitation and corrosion. Corrosion current densities during applied polarisation scans were enhanced under the influence of cavitation because of the destruction of passivating films. Evidence was found for a work hardened layer.

Journal ArticleDOI
TL;DR: In this paper, the authors investigated the effect of applied stress on a 4.5 vol. of Al-4.0mass% Cu-1.5mass% Mg alloy with mean grain diameter about 0.9 μm in the temperature range 623-723 K and with applied stresses ranging from 7.5 × 10 −4 G to 3.1 × 10−3 G (where G is the shear modulus).
Abstract: Creep in an Al-4.0mass% Cu-1.5mass%Mg alloy strengthened by about 4.5 vol.%Al 4 C 3 particles (Novamet IN-9021 alloy) of mean grain diameter about 0.9 μm was investigated in the temperature range 623–723 K and with applied stresses ranging from 7.5 × 10 −4 G to 3.1 × 10 −3 G (where G is the shear modulus). The creep is characterized by an apparent activation energy about five times higher than the activation enthalpy of lattice self-diffusion in pure aluminium; the steady state creep rate varies as approximately the sixteenth power of applied stress. Two different interpretations of experimental data are considered: 1. (i) The creep results from the motion of lattice dislocations associated with a strongly temperature- and applied-stress-dependent back stress σ B . 2. (ii) The creep is due to diffusional transport of matter controlled by motion of grain boundary dislocations with which a back stress σ 0 , again strongly temperature and applied stress dependent, is associated. Both interpretations are critically discussed; because of small grain size of the alloy investigated and, in particular, because of strong applied stress and temperature dependences of the back stress, the latter interpretation, although qualitative, is believed to be more realistic.

Journal ArticleDOI
TL;DR: In this paper, the role of microstructure and environment in influencing mechanisms of damage during high-temperature, low cycle fatigue were investigated in a lithium-containing aluminium alloy in the peak-aged condition, and tested over a range of plastic strains.

Journal ArticleDOI
TL;DR: In this paper, a previous treatment of nucleation in gas atomised liquid aluminium alloys has been extended to model more realistically the cooling conditions in a gas atomiser, and the predicted undercoolings are now slightly higher than in the earlier work.
Abstract: A previous treatment of nucleation in gas atomised liquid aluminium alloys has been extended to model more realistically the cooling conditions in a gas atomiser. Previous predictions of the phase which will predominantly nucleate in powder particles, as a function of powder size and composition, are reinforced. Predicted undercoolings are now slightly higher than in the earlier work. Results from this work are compared with recent experiments.MST/1013

Journal ArticleDOI
TL;DR: The surface of an Al-4wt%Cu alloy was irradiated with an excimer laser and X-ray measurements showed that this treatment changed the residual stress in the alloy surface layers from tensile to compressive in the first 10 μm below the surface of the laser-treated alloy, the microhardness was found to be higher than that of the as-received alloy as discussed by the authors.
Abstract: The surface of an Al-4wt%Cu alloy was irradiated with an excimer laser Very precise X-ray measurements showed that this treatment changes the residual stress in the alloy surface layers from tensile to compressive In the first 10 μm below the surface of the laser-treated alloy, the microhardness was found to be higher than that of the as-received alloy

Journal ArticleDOI
TL;DR: In this article, the kinetics of static recrystallization of a commercial purity aluminium alloy have been determined after hot torsion testing followed by quenching, and a clear correlation has been found between the time t0.5 to reach a 50% recrystized fraction, the parameters of deformation, the strain and the annealing temperature Ta.
Abstract: The kinetics of static recrystallization of a commercial purity aluminium alloy has been determined after hot torsion testing followed by quenching. The annealing treatments of quenched specimens have been carried out in the temperature range 325–500°C. For each combination of deformation conditions and annealing temperature, the recrystallized fraction, as measured by quantitative optical metallography, changes with time following an Avrami type of relationship. A clear correlation has been found between the time t0.5 to reach a 50% recrystallized fraction, the parameters of deformation, the strain and the annealing temperature Ta. It is shown that deforming the material within the steady state regime has a marked effect on t0.5; an increase in strain yields a decrease in t0.5. This behaviour is consistent with the dependence of the number of recrystallization nuclei (recrystallized areas formed during hot deformation) on strain. The time t0.5 to reach a 50% recrystallized fraction is also observed to decrease for an increase in annealing temperature and/or an increase in the Zener-Hollomon parameter.

Journal ArticleDOI
TL;DR: In this paper, the authors investigated the flow behavior of 2024 aluminium during drop weight compression tests and found that the shear surfaces display a conical geometry and appear to develop in the presence of thermal softening after a flow stress maximum.
Abstract: The flow behaviour of 2024 aluminium during drop weight compression tests was investigated. Use of cylindrical specimens of different height to diameter ratios, of different orientations and having undergone varying levels of prestrain, enabled the development of shear bands occuring within these specimens to be studied. The shear surfaces display a conical geometry and appear to develop in the presence of thermal softening after a flow stress maximum has been reached. Fracture along these surfaces appears to be associated with the rotation of strings of inclusions into the plane of the surface as well as severe deformation along the bands which leads to both thermal softening and exhaustion of matrix material ductility.

Journal Article
TL;DR: Etude de la resistance a la traction des materiaux renforces par dispersion. Influence de la temperature and de la porosite sur la microstructure des lingots.
Abstract: Etude de la resistance a la traction des materiaux renforces par dispersion. Influence de la temperature et de la porosite sur la microstructure des lingots. Caracterisation de celle-ci par microscopie electronique a balayage