Hardening Of Copper Research Articles

Resoftening of Quench-hardened Copper

Kinetics of the resoftening of quench-hardened copper was investigated, and the activation energy for the resoftening was found to be about 5 eV. Two possible mechanisms of quench hardening in copper, i. e. stacking fault tetrahedra and extended prismatic loops, were discussed based upon this observation with reference to the transmission electron microscopy of quenched copper.

Copper and Copper Alloys in Ancient Argentina

ON the basis of their techniques, it is possible to distinguish two essentially different metallurgical provinces of South American cultures.1 One of these extends from the Guiana region to Colombia and Central America, on the Atlantic side, and, on the Pacific side, to the coast of middle and southern Peru and is characterized by its jewelery and use of gold and a gold-copper alloy {tumbago). Here are found small gold ornaments which are the only metallic objects in the Paracas culture. The other zone, which made useful objects from copper and bronze by a coarser metallurgy, developed, with Bolivia as a starting point, from the highlands of Peru to the Chilean Atacama Desert and to northwestern Argentina. The great blocks of the buildings at Tiahuanaco, Bolivia, are held together by copper clamps, and it is generally accepted, with Norden ski?ld,2 that this was the first case of the use of metals in the highlands. The beginning of the 4 4 Old'5 period at Tiahuanaco is usually given as the fourth century a.d., though radiocarbon dating may still shift the begin ning of the Copper Age backward in Bolivia. Bronze was probably discovered in the highlands in the Classical period of Tiahuanaco, around the eighth century, although some other authors assume that the hardening of copper by tin was first introduced into Bolivia in the eleventh century, before the beginning of the Inca domination, while knowledge of alloying first spread to the coast between the twelfth and fourteenth centuries.3

Irradiation hardening in copper and nickel

The lattice and dislocation components of irradiation hardening have been measured in polycrystalline copper and nickel as a function of 1. (a) testing temperature and 2. (b) neutron dose. The results are compared with Seeger's theory of lattice hardening, which is based on dislocations cutting through a forest of obstacles under the action of both stress and thermal activation. The observed temperature dependence of the lattice hardening in both metals is in excellent agreement with the theory in the as-irradiated condition. Mild annealing treatments greatly reduce the temperature sensitivity however and the theory is no longer obeyed. From the results it is concluded that the obstacles do not have a constant activation energy as assumed by Seeger and theories of the temperature dependence should include this factor. It is shown that the dose dependence of lattice hardening may be described by the new formula σ i = A(1 − e −Bφ) 1 2 which is derived by combining the theoretically predicted dependence on φ 1 2 with a saturation effect. The existence of obstacles of various sizes is also indicated from measurements of the temperature dependence of the constants in this equation. No definite conclusions as to the mechanism of formation of the obstacles can be made at present. The dislocation hardening component is shown to be independent of testing temperature in copper but not in nickel.

Observations Concerning the Radiation Hardening in Copper and Nickel

Single crystals of copper were irradiated with neutrons in a reacter to a dose of 2 x 10/sup 19/ nvt (integrated flux) at approximately 70 deg C and were subsequently deformed by various tensile stresses. The crystals were electrolytically polished to l000 A thickness and examined electron microscopically. The most obvious feature of the irradiated copper was dark spots with diameters from 50 to 250 A. These were probably caused by small vacancy condensation loops. Heavily kinked and intertwined glide dislocations, previously observed in deformed irradiated nickel, were also present. It was suggested that the kinks and intertwined loops were forced when glide dislocations had attracted vacancies and vacancy groups which, after they had condensed on them, formed kinks. It was concluded that the high yield stress after irradiation is caused by the profuse kinking of the glide dislocations. The low rate of work hardening is explained by the clearing of channels free of obstacles. (J.S.R.)

The hardening of copper by neutron irradiation

Copper wires of 0.060 in. diameter were irradiated at 50 deg C for 1 to 3 weeks. At a fixed neutron dose and testing temperature the yield stress of irradiated polycrystalline copper increases within accuracy limits of experimental measurements. Lattice friction hardening and source hardening proceed simultaneously. The increased yield strength of irradiated copper at -78 deg C compared with 20 deg C arises from a temperature dependence of the lattice friction component of hardening. (C.J.G.)