Showing papers on "Aluminium alloy published in 1978"

Production of cast aluminium-graphite particle composites using a pellet method

Abstract: Copper- and nickel-coated graphite particles can be successfully introduced into aluminium-base alloy melts as pellets to produce cast aluminium-graphite particle composites. The pellets were made by pressing mixtures of nickel- or copper-coated graphite particles and aluminium powders together at pressures varying between 2 and 20 kg mm–2. These pellets were dispersed in aluminium alloy melts by plunging and holding them in the melts using a refractory coated mild steel cone, until the pellets disintegrated and the powders were dispersed. The optimum pressure for the preparation of pellets was 2 to 5 kg mm–2 and the optimum size and percentage of aluminium powder were 400 to 1000mgrm and 35 wt% respectively. Under optimum conditions the recovery of the graphite particles in the castings was as high as 96%, these particles being pushed into the last freezing interdendritic regions. The tensile strength and the hardness of the graphite aluminium alloys made using the pellet method are comparable to those of similar composites made using gas injection or the vortex method. The pellet method however has the advantage of greater reproducibility and flexibility. Dispersion of graphite particles in the matrix of cast aluminium alloys using the pellet method increases their resistance to wear.

Bakable aluminium vacuum chamber and bellows with an aluminum flange and metal seal for ultrahigh vacuum

Abstract: A bakable (200°C) aluminium alloy vacuum chamber and bellows (6063‐T6) with an aluminium alloy (2219‐T87) flange and metal seal (Helicoflex‐HN: aluminium O‐ring) has been constructed. Such components may be used in the assemblies of the vacuum chambers in proton synchrotrons and electron storage rings.

Delayed retardation phenomena of fatigue crack growth in various steels and alloys

Abstract: The delayed retardation phenomena of fatigue crack growth resulting from a single application of overload were investigated for five steels, two aluminium alloys and a titanium alloy. As long as the small scale yielding condition was satisfied at the overloaded crack tips, the retardation behaviour of these materials was expressed consistently by four parameters; the peak/baseline stress ratio, r, the exponent in the Paris equation, m, the overload-affected zone size, ωD, and the crack distance at the minimum rate of crack growth, ωB. Then the parameters, ωB and ωD, characterizing the retardation phenomena for these materials were determined. The retardation of aluminium alloys was stronger than that of the other materials. This is attributed to the lower value of ωB/ωD in aluminium alloys than in the other materials. In the case of r=2, the overload-affected zone sizes, ωD, were nearly equal to 1.5ω0 in HT80 steel and aluminium alloys, slightly lower than 1.5ω0 in SNCM8 steel and much larger than 1.5ω0 in A553 steel and the titanium alloy, where ω0 is the monotonic plastic zone size calculated according to the Dugdale model. The dependence of retardation on baseline stress intensity, ΔK1, appeared somewhat complicated. In the cases of A553 steel and A2017 aluminium alloy the amount of retardation increased with increasing ΔK1 value, while in the cases of HT80 steel and Ti-6A1-4V titanium alloy the tendency appeared in the reverse direction. The former behaviour was related to the change in the stress state from plane strain to plane stress at the overloaded crack tips and the latter was related to the threshold of stress intensity.

Composite cast cylinder blocks for IC engine - consists of aluminium alloy block cast round liners made of wear resistant, hypereutectic aluminium silicon alloy

Abstract: The cylinder liners are made of a wear resistant Al alloy (I), and can be located on cooled mandrels during a casting process in which the liners (I) are surrounded by a cast Al alloy (II) possessing good-castability and -machineability. The casting temp. of alloy (II) is pref. is not >100 degrees C above the m.pt. of alloy (I). The mandrels are pref. cooled to extract heat from the liners (I) during the solidification of alloy (II). The liner alloy (I) pref. contains by wt. 12-25% Si, 1-5% Cu, and 0.5-5% Mg as the main alloying elements, the remainder being Al. The entire block is made of Al alloys and therefore has low wt. and good thermal conductivity; but wear resistance and machineability are provided where necessary.

Extraction and X-ray analysis of phases in aluminium alloys

Abstract: The extraction of precipitates and second phase insoluble intermetallic or metalloid compounds from three commerical aluminium alloys was achieved by anodic dissolution of the aluminium alloy matrix in a methanolic electrolyte containing benzoic acid, oxine and chloroform. Investigated were Aluminium Association alloy 7075 containing principally Al-Zn-Mg-Cu, alloy 6061 containing principally Al-Si, and alloy 2011 containing principally Al-Cu. X-ray diffraction of the extracted residues using the Debye-Scherrer method, identified the compounds MnAl6, MgO and Mg2Si in the 7075 alloy in the aged condition, the insoluble phase Mn12Si7Al5 in the 6061 alloy in both the solution heat-treated and aged conditions. In the 2011 alloy the primary precipitate, CuAl2, was extracted in the aged condition and the lattice parameters for this tetragonal compound were determined to bea=6.064 A andc=4.874 A: Metallic bismuth also was identified in the extraction from this alloy. Several lines, believed to represent an unknown ternary or higher compound, could not be identified.

Analysis of Specific Pressure Necessary to Extrude Aluminium Alloy Compacts

Abstract: The mechanical properties of aluminium alloy powder compacts vary throughout the quasi-static deformation zone. Experimental evidence has suggested that the flow stress is dependent upon both strain and strain rate such that an equation of the form δ = Aeme n best describes material behaviour under deformation conditions. This paper presents a mathematical analysis of the deformation by modifying an axi-symmetric upper-bound solution and utilizing a penalty function approach to minimization to obtain the stress constants. It is shown that for a cast billet this approach predicts the specific pressure accurately and that for powder compacts the constants k, m, and n may be obtained and a satisfactory prediction of pressure facilitated.

Aluminium alloy with excellent machinability and corrosion resistance

Abstract: PURPOSE:To provide an Al alloy with excellent machinability and corrosion resistance by adding Bi, Sn, and Cd in combination to an Al-Si-Mg alloy.

Non-erosion aluminium alloy for die-casting

Abstract: A corrosion resistant bright aluminum alloy for die-casting was consisted essentially of Zn 0.5-2.5, Mg 0.5-3.0, Si 0.2-1.2, Fe 0.2-1.5, Mn 0.1-1.2, Cu 0.05-0.3%, and the balance aluminum. The alloy for die-casting further additionally comprised at least one element selected from the group consisting of Ti 0.05-0.3, Zr 0.05-0.3, V 0.05-0.3, Co 0.05-0.5, B 0.01-0.5, Sb 0.05-0.3, Ni 0.05-2.0, and Be 0.001-0.005 wt. %.

Composite aluminium alloy sheet for heat exchangers - comprises aluminium core coated with alloy of aluminium, zinc and lithium, calcium, sodium or potassium

Abstract: The composite sheet is made of a core of Al alloy one or both surfaces being provided with a plated coat of an Al alloy of compsn. 0.1-2.0 wt.% Zn, 0.01-2.0 wt.% Li, Ca, Na or K, balance Al. The sheet is produced by applying the plating material to the surface of a bar of the Al alloy, which is then hot and cold rolled to sheet. Used for the fabrication of heat exchangers by vacuum brazing. The plated coat has a thickness of 3-20% of the total thickness of the composite. The composite sheet can be vacuum brazed without the loss of Zn due to evaporation.

Change of the ultrasonic characteristics with stress in some steels and aluminium alloys

Abstract: Under application of tensile stress to specimens of several steels and aluminium alloys up to a stress close to their yielding stress, a continuous ultrasonic wave of approximately 5 MHz was propagated through the specimens in directions parallel and perpendicular to the tensile axis The change of ultrasonic resonance frequency with applied stress was measured The results of the measurement of the ultrasonic resonance frequency showed that the frequency ratio varied with the magnitude of applied stress, the material of the specimen, and ultrasonic wave propagating direction with respect to the direction of the stress They also showed that the ultrasonic wave resonance frequency measuring method is useful in finding the ultrasonic characteristics of materials under applied stress

Method of producing aluminium alloy low density sintered parts

Abstract: PURPOSE:To produce a high strength aluminium alloy low density sintered parts through sintering in a pressed powder form of a mixture of Al powder, a Al-Si alloy powder, Al-Cu-Mg-Si alloy powder and the like in such a manner as to have a fixed composition of Cu, Mg and Si.

Long-Transverse Stress Corrosion Cracking Behaviour of Aluminium Alloy AA 7075

Abstract: Exposure of bolt-loaded DCB specimens to marine atmosphere and artificial sea water environments showed that YX-oriented stress corrosion crack growth in 7075 alloy plate is extremely slow, and is not greatly dependent on temper condition. Apparent ‘threshold’ stress intensities (KIsce)are about 25 MPa√m compared to ZX values which rangefrom about 5 (-T651 temper) to 23 (-T7351 temper)MPa√m Most of the crack growth in YX-oriented DCB specimens occurs in a plane normal to the precrack (ZX-oriented). These secondary cracks are presumably caused by the transverse tensile stress acting at the crack tip, and assume a size and shape similar to that of the plastic zone at this location.

Method of bonding high voltage aluminum ball

Abstract: To permit ball-bonding of wires of aluminium or aluminium alloy to small electrical circuits or components, a spark discharge is created between the end of the wire and an electrode in a shielding atmosphere with a peak current density in the wire section which is from 40 to 450 times that used for ball-bonding gold wire. In this way oxidation of the ball is prevented.