Abstract
Round tensile test specimens of an age-hardened CuCr1Zr alloy were subjected to direct electrical current heating in a Gleeble thermal–mechanical simulator at 800 °C. The mechanical properties were monitored by the Vickers hardness test, and the changes in the grain structure were examined by light metallography. A quantitative analysis of the size and distribution of fine precipitates during annealing was carried out using transmission electron microscopy (TEM). The grain structure showed a gradient corresponding to the gradient of the temperature on the test piece. Annealing for 60 s at 800 °C resulted in a partially (~50%) recrystallized structure with new grains about 45 μm in diameter. In the as-delivered condition, TEM documented tiny (1 to 4 nm) coherent chromium precipitates inducing strain fields in the matrix. During overaging, the particles lost their coherence and gradually coarsened up to a mean diameter of 40 nm after 300 s at 800 °C. The coarsening kinetics obeys Lifshitz, Sloyzov, and Wagner’s theory.
Highlights
Precipitation-hardened CuCr1Zr alloy combines high thermal and electrical conductivity with high strength and good softening resistance. It is used in many application areas, especially as resistance welding electrodes and wheels, switches, circuit breakers, high-temperature wires, lead frames of integrated circuits, contact wires of high-speed railways, casting wheels, and ingot molds in metallurgy, or as rotor rings and connectors in the electric industry
When the alloy is exposed to high temperatures, as in resistance spot welding electrodes, mechanical properties can be degraded by softening, thermal fatigue, recovery, and recrystallization
The purpose of this study is to visualize the changes in the grain structure of the alloy after direct heating by electric current in a Gleeble thermal–mechanical simulator at 800 ◦C
Summary
Precipitation-hardened CuCr1Zr alloy combines high thermal and electrical conductivity with high strength and good softening resistance It is used in many application areas, especially as resistance welding electrodes and wheels, switches, circuit breakers, high-temperature wires, lead frames of integrated circuits, contact wires of high-speed railways, casting wheels, and ingot molds in metallurgy, or as rotor rings and connectors in the electric industry. It is considered for heat sink of the International Thermonuclear Experimental Reactor (ITER) divertor [1]. These results are supplemented by a quantitative analysis of the size and distribution of fine precipitates for different annealing times at 800 ◦C
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