Copper cold worked

Modifications to Precipitates. Silicon is sometimes added to Al—Cu—Mg alloys to help nucleate S precipitates without the need for cold work prior to the elevated temperature aging treatments. Additions of elements such as tin [7440-31-5] Sn, cadmium [7440-43-9] Cd, and indium [7440-74-6] In, to Al—Cu alloys serve a similar purpose for 9 precipitates. Copper is often added to Al—Mg—Si alloys in the range of about 0.25% to 1.0% Cu to modify the metastable precursor to Mg2Si. The copper additions provide a substantial strength increase. When the copper addition is high, the quaternary Al CuMg Si Q-phase must be considered and dissolved during solution heat treatment. 

Additions of cadmium (0.05—1.3%) to copper raise the recrystallization temperature and improve the mechanical properties, especially in cold-worked conditions, with relatively Htde reduction in conductivity. Copper containing 0.07% cadmium is used in automotive cooling fins, heavy-duty radiators, motor commutators, and electric terminals. 

The effect of cold working by cold rolling of sheet on the yield, at 0.2% offset strain, and tensile strengths of copper sheet is shown in Figure 1. 

Figure 1 also shows the decrease in tensile elongation (a common measure of ductiUty) that accompanies the strength increase with cold working. Whereas these particular rolling curves include up to 70% reduction in thickness, pure copper is capable of being roUed much further without fracturing. 

The annealing curves for several copper alloys are compared to copper in Figure 4. Solute additions affect the annealing response, as they do for cold working, by interaction with microplastic processes that account for softening as dislocations and subgrains are eliminated during the anneal. 

Electrical conductivity of copper is affected by temperature, alloy additions and impurities, and cold work (9—12). Relative to temperature, the electrical conductivity of armealed copper falls from 100 % lACS at room temperature to 65 % lACS at 150°C. Alloying invariably decreases conductivity. Cold work also decreases electrical conductivity as more and more dislocation and microstmctural defects are incorporated into the armealed grains. These defects interfere with the passage of conduction electrons. Conductivity decreases by about 3—5% lACS for pure copper when cold worked 75% reduction in area. The conductivity of alloys is also affected to about the same degree by cold work. 

Fig. 9. The effect of prioi cold work on softening resistance, as illustrated for C230 (copper—15% 2inc) where (—) is CR 55% (---) CR 10% in thickness.

Figure 6.11. Isothermal energy release from cold-worked copper, measured calorimelrically...

Spiral-plate exchangers are fabricated from any material that can be cold worked and welded. Materials commonly used include carbo steel, stainless steel, nickel and nickel alloys, titanium, Hastelloys, and copper alloys. Baked phenolic-resin coatings are sometimes applied. Electrodes can also be wound into the assembly to anodically protect surfaces against corrosion. 

These are produced by adding small amounts of copper, magnesium and/or silicon, which can increase their strength much more by heat-treatment than by cold-working (Table. 3.31). 

W.B. Hutchinson, F.M.C. Besag and C.V. Honess, The annealing behaviour of cold worked copper-25at.% gold, ActaMetall. 21 1685 (1973). 

Cold worked copper alloys, 7 723t Cold working... 

The effect of dislocations has also been studied by Bloembergen and Rowland 106) in cold-worked copper (Cu and Cu resonances), and also the effect of alloying in Al-Zn alloys (Al resonance) by Rowland 107). Otsuka and Kawamura 108) have studied the NMR of 1" in KI, Na in NaCl-NaBr mixed crystals, and Br in KBr-NaBr mixed crystals and have estimated dislocation densities in these materials. 

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