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Nondestructive Evaluation of Microstructure Degradation of Pearlitic Steel

Pearlite spheroidization is the common form for the structural deterioration of pearlitic steel. The excessive pearlite spheroidization induces the serious decline in the mechanical properties of material and the change of ultrasonic parameters. Different heat treatment processes were applied to T8 steel samples for obtaining the pearlite structure in different spheroidized states with measurement of the corresponding longitudinal wave velocity, attenuation coefficient and nonlinear parameters. The experimental results showed that the normalized nonlinear parameter enhanced with the increment of pearlite spheroidization, while the longitudinal wave velocity and attenuation coefficient had no significant changes.