Heavy Alloy

heavy alloy

[¦hev·ē ′al‚ȯi]
(metallurgy)
A tungsten-nickel alloy produced by pressing and sintering the metallic powders; used for screens for x-ray tubes and radioactivity units and for contact surfaces of circuit breakers.

Heavy Alloy

 

any of a group of tungsten-based composition materials containing (by weight) up to 10 percent nickel and iron (tungsten-nickel-iron type alloys), in proportions from 7:3 to 1:1, or nickel and copper (tungsten-nickel-copper alloys), in proportions from 3:2 to 1:1. Small amounts of chromium, molybdenum, rhenium, cobalt, and other metals are sometimes also present.

Heavy alloys have a two-phase structure, in which tungsten grains, the γ-phase, are uniformly distributed in a nonrefractory matrix of nickel and iron or copper, the α-phase. Iron and copper limit the solubility of tungsten in nickel, inhibiting the formation of the β-phase (Ni4W), and they lower the temperature at which the α-phase begins to melt.

Heavy alloys are ductile and easily cut and shaped. Their properties depend on the extent and graininess of the α-phase, the Ni: Fe or Ni: Cu ratio, the alloying elements, and the production conditions. Tungsten-nickel-copper alloys are not as strong as tungsten-nickel-iron alloys because of the formation of a coarse dendritic structure when they are cooled below the sintering temperature, but they are more practical to manufacture because the temperature at which the α-phase begins to melt is about 100°C lower.

Heavy alloys have a density of at least 16.5–17 g/cm3 at 20°C. They have a thermal coefficient of linear expansion of (4.0–5.5) × 10–6 between 20° and 400°C, a tensile strength of up to 150 kilograms-force per sq mm (kgf/mm2; 1 kgf/mm2 = 107 newtons per sq m), a compressive strength of up to 120 kgf/mm2, a yield point of up to 140 kgf/mm2, a relative elongation of up to 30 percent, and an impact strength of at least 1 kgf-m/cm2 for unmatched samples. They are corrosion-resistant and are good absorbers of γ rays and X rays.

Heavy alloys are produced from mixtures of powdered metals using techniques of powder metallurgy. During the process of sintering at 1350°-1500°C in the presence of the liquid phase, the tungsten powder recrystallizes to form almost spherical particles that are dozens of times larger than the particles of the initial powder. The properties of heavy alloys are improved by subsequent pressure working and heat treatment.

Heavy alloys have a wide range of application because of their

Table 1. Rate of growth of the total industrial output of the USSR (base year, 1913 = 1)
 192819401950196019701975
Fuel industry. . . . . . . . . . . . . . . . . . . . . .1.56.59.322.741.154.7
Ferrous metallurgy. . . . . . . . . . . . . . . . . . . . . .15.810.227.553.368
Chemical and petrochemical industries. . . . . . . . . . . . . . . . . . . . . .1.517.534.3134468772
Machine building and metalworking. . . . . . . . . . . . . . . . . . . . . .1.829.763.62688401,449
Total. . . . . . . . . . . . . . . . . . . . . .1.37.713.340.391.5131

advantageous combination of desirable properties. They are used in making screens that are more effective than lead as shields against penetrating radiation, and in the production of containers for radioactive isotopes, such as 90Sr. In addition, they are used in the manufacture of balances and counterweights for aircraft, counterweights for self-winding clocks and watches, rotors for gyroscopes, inertial masses, cores for armor-piercing shells, dies for electrical upsetting processes, and matrix inserts for hot pressing of brass and bronze rods. Heavy alloys are used as electrode materials in chipless metalworking processes and resistance welding and as temperature compensators in silicon semiconductor devices. The range of uses for heavy alloys is continually and rapidly expanding.

O. P. KOLCHIN and IU. A. EIDUK

References in periodicals archive ?
Address : The General Manager, Heavy Alloy Penetrator Project (Happ), Ministry Of Defence, Govt.
May 10 /PRNewswire-FirstCall/ -- Aerojet, a GenCorp (NYSE: GY) company, announced today that it has been selected by The Boeing Company to supply heavy alloy weights for Boeing's revolutionary Composite Main Rotor Blade (CMRB) in support of the AH-64D Apache Block III (AB3) program.
It is made of a heavy alloy of nickel, cobalt and steel, shaped to be very thin and pointed so the warhead punches into rock like a nail into wood.
Heavy alloy was selected for the line due to the presence of wet carbon dioxide in the gas stream.
Address : Heavy Alloy Penetrator Project Happ Township Trichy 620 025
Tenders are invited for Supply Of Pure Tungsten Powder As Per Arde Specification No: Arde/Specn/Pnwh/Mat/Tap:2012 In Lieu Of Heavy Alloy Scrap
Tenders are invited for 1)Supply Of Pure Tungsten Powder As Per Arde Specification No:Arde/Specn/Pnwh/Mat/Tap:2012 In Lieu Of Heavy Alloy Scrap And Scope Of Work Enclosed 2) Offers Of Established Suppliers Who Have Successfully Supplied Tungsten Powder In Lieu Of Heavy Ally Scrap To Happ During The Past Will Not Be Considered
Address : Heavy Alloy Penetrator Project, Trichirappalli Tamil Nadu India Pin 620025
Address : Works Manager, Heavy Alloy Penetrator Project, Tiruchirappalli,Tamilnadu, India, Pin.
Among their topics are the non-Gaussian diffusion of phosphorus and arsenic in silicon with local density diffusivity model, the artificial aging behavior of 6063 alloy studied using Vickers hardness and positron annihilation lifetime techniques, the liquid-phase sintering of tungsten heavy alloys, new experimental proof of phase and structure formation in metallic materials eletrodeposited through a liquid state stage, the variable range hopping model in manganese oxides, and dynamics of trililoxane wetting of hydrophobic surfaces.
This 18-page practical Design Guide for Tungsten (W) Heavy Alloys (WHA) is authored by Dr.
Finally, part four explores metal injection molding of particular materials, including stainless steels, titanium and titanium alloys, thermal management alloys, high speed tool steels, heavy alloys, refractory metals, hard metals and soft magnetic alloys.