Abstract
BIRMINGHAM. Institute of Metals.—Annual autumn meeting, September 21.—Prof. A. A. Read and R. H. Greaves: The properties of some nickel-aluminium-copper alloys. In some of the copper-rich nickel-aluminium-copper alloys the α-solution will retain more nickel and aluminium at 900° C. than at the ordinary temperature. These alloys, while relatively soft on quenching from 900° are hardened by slow cooling or by reheating to lower temperatures. This change is the result of the appearance of a new constituent, probably a nickel-aluminium-copper solid solution, the separation of which is accompanied by changes in density and electrical conductivity, in addition to its effect on tensile, hardness, notched bar, and other tests. The separation of this special constituent takes place slowly, so that chill-cast alloys and hot-rolled rods of small section consist almost wholly of the α-constituent. On annealing the cold-rolled alloys softening proceeds slowly up to 500° C., when precipitation of the nickel-aluminium-rich constituent begins to take place. If the separation is sufficient, this may give an alloy of high elastic limit and tensile strength and good elongation. The hardest product is obtained by reheating the quenched alloy for some time at 600–700° C. Alloys so treated generally give better properties than those obtained by uniform rates of slow cooling, and show considerable endurance under alternating stresses above their true fatigue limit.—R. T. Rolfe: The effect of increasing proportions of lead upon the properties of Admiralty gunmetal, with an appendix dealing with the effect of lead on gunmetal containing copper 85 per cent., tin 5 per cent., and zinc 10 per cent. Synthetic alloys containing increasing proportions of lead up to 1.68 per cent. were examined. In sand-cast gunmetal lead gradually increases the strength, ductility, and softness of the alloy up to about 1.5 per cent. of lead, but above this proportion causes a decrease in all three. It does not affect the soundness. In chill-cast gunmetal the effect on the hardness parallels that of the sand-cast metal, with a change-point at about 1.5 per cent. of lead, but associated with a minimum rather than a maximum strength figure. It does not affect the soundness. The influence of lead on liquation, machinability, corrosion, and behaviour for bearing purposes is discussed, and it is suggested that in sand-cast gunmetal the proportion of lead permitted by the Admiralty specification might with advantage be increased from 0.5 to 1 per cent.—R. Genders: The casting of brass ingots. The failure of hollow-drawn articles made from brass rod has generallv been found to be due to the presence of non-metallic inclusions which originated in the cast ingot. The methods used in casting ingots of brass vary, much consideration being given to the saving of rolling. When a hollow article subject to expanding stresses is to be made, the avoidance of inclusions of foreign matter is vital, and the form of ingot requires modification. The ingots made were 3 in. square and 30 in. in length, as compared with the ingots 6–7 ft. in length and 1½ in. square section in common use. A hot sinking head or “dozzle” was introduced, and molten brass is poured through the “dozzle.” No pipe is formed in the ingot proper, and additions of metal may be made at any time to the metal in the “dozzle” without risk of introducing defects into the ingot, any dross rising to the top of the still fluid head. The moulds were tapered, the top being enlarged by increasing amounts in successive experiments, and ingots were cast at the usual foundry speed.—T. G. Bamford: The density of the zinc-copper alloys. Experiments were conducted with alloys made from pure metals and cast in sand- and chill-moulds respectively. There is a contraction in volume due to alloying with mixtures containing more than 25 per cent. of copper, and the density of the sand-cast or slowly cooled alloys is generally less than that of the chill castings; at points where the liquidus and solidus coincide on the constitutional diagram, chill castings and sand castings give the same values. The expansion recorded by Turner and Murray with alloys containing less than 30 per cent. of copper is confirmed, and is shown to be connected with a new form of porosity different from ordinary unsoundness.—Dr. F. Johnson: Experiments in the working and annealing of copper. Part 1: Critical ranges of deformation probably result from stages of abnormal plasticity during rolling of the metal. It is suggested that during these stages the metal actually loses some of the increase of hardness conferred in earlier “passes.” A decrease of volume up to 85 per cent. occurs; the increase of volume which then sets in may correspond to the inception of permanent disability which cannot be eradicated by annealing. Part 2: At 200° C. for one hour softening occurs in all strips rolled beyond 40 per cent. reduction. Test-pieces from the axes of the strips undergo softening to a greater extent than edge-specimens from the same series when annealed under the same conditions, thus indicating a greater intensity of strain at the centre than at the edges. High-temperature annealing at 750° C. shows that at 87 per cent. reduction a rapid decrease in strength sets in. Part 3: Low-temperature annealing of cold-drawn copper rods of varying compositions. “Tough-pitch” arsenical rods retain their strength practicallv unimpaired up to 300° C., whereas “tough-pitch” electrolytic copper undergoes considerable loss of strength. The presence of silver in arsenical rods raises slightly the annealing temperature. The substitution of iron for oxygen in arsenical copper retards the rate of softening.—W. E. Alkins and W. Cartwright: The effect of progressive cold-drawing upon some of the physical properties of low-tin bronze. The tin content varied from about 07 to about 1.0 per cent. in the three samples of bronze studied. The most important and rapid changes in properties occur after a reduction of 85 per cent. of the original area, i.e. over the range where practical difficulties are met with during drawing. The extent of the variation in tensile strength, specific volume, and scleroscooe hardness is very similar to that previously found in the case of copper.
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Societies and Academies. Nature 108, 197–199 (1921). https://doi.org/10.1038/108197b0
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DOI: https://doi.org/10.1038/108197b0