Influence of precipitates and dislocations on the acoustic nonlinearity
نویسندگان
چکیده
The influence of precipitates and dislocations on the acoustic nonlinearity was investigated in isothermally aged ferritic CrMo steel and low cycle fatigued copper. The variation in the normalized acoustic nonlinearity parameter (β/β0) was interpreted as resulting from microstructural changes supported by the electron microscopy. The β/β0 of CrMo steel increased abruptly in the initial stage of degradation, and then changed little due to the coarsening of carbide and precipitation of stable M6C carbide during isothermal aging. Due to the evolution of dislocation cell substructure, the β/β0 of copper increased with the fatigue cycles. These experimental results are illustrated that the acoustic nonlinearity is severely affected by the lattice strain caused by precipitates and dislocations.
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