Time-Resolved Flow Stress Behavior of Structural Materials at Low Temperatures
During low-temperature testing of metals and alloys, the load developed in a specimen is measured in-place with a time resolution of up to 5μs. A load drop resulting from a rapid excessive event of plastic relaxation (“plastic instability”) emerges as a coupled two-stage process: A linear drop at very high rate at macroscopic level is followed by a quasi-exponential drop at much smaller rate. The surface temperature of the specimen measured with a thermocouple during loading shows no significant rise until the load has started to fall. These experimental findings are discussed in terms of dislocation motion controlled by viscous and thermally activated mechanisms, respectively.
KeywordsPlastic Instability Plastic Relaxation Constant Crosshead Speed Maximum Sampling Rate Solid State Data
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