WORK SOFTENING IN IRRADIATED COPPER
The temperature dependence of the flow stress of polycrystalline copper, both unirradiated and after neutron irradiation, has been investigated by repeated tensile testing first at temperature T: and then at temperature T/sub 2/. In this way reversible and irreversible temperature effects can be separated. In irradiated copper the temperature sensitivity of the flow stress is very large during the early stages of the deformation, and irreversible effects occur when the temperature of the deformation is changed. A sharp yield drop, accompanied bv a Luders band, appears whcn an irradiated specimen is strained at a high temperature (e.g., 20 C) after being deformed at a low tcmperature (e.g.s 195 C). This phenomenon is not sensitive to the temperature range over which the experiments are carried out but occurs only during the early stages of the deformation. After about 15 per cent extension the flow stress becomes entirely reversible on changing the temperature, and the temperature dcpendence is only slightly greater than in unirradiated material. The effect is not observed in alpha brass anmd is removed from irradiated copper by mild annealing treatments. The phenomenon is believed to be associated with the high temperature sensitivity of the lattice hardening produced on irradiation. An explanation is proposed in which groups of dislocations piled up during low temperature deformation behind the obstacles responsible for the lattice hardening collapse on subsequent higher temperature deformation either by by-passing the obstacles or by actually removing the smaller obstacles. (auth)
- Research Organization:
- Atomic Energy Research Establishment, Harwell, Berks, Eng.
- NSA Number:
- NSA-13-013976
- OSTI ID:
- 4256718
- Journal Information:
- Acta Met., Journal Name: Acta Met. Vol. Vol: 7
- Country of Publication:
- Country unknown/Code not available
- Language:
- English
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