The flow stress was decreased by superposing an ultrasonic oscillatory stress during plastic deformation. Amplitude-dependent internal friction was investigated, together with the stress decrement due to superposed oscillations during plastic deformation, in single crystals doped with KBr, KI or SrCl2. The relationship between the amplitude-dependent internal friction and the stress decrement was divided into 3 regions for KCl doped with KBr or KI. The internal friction was proportional to the stress decrement in the first region, up to the first bending point at the lower stress amplitude. The stress decrement at the first bending point was proportional to the square root of the KBr or KI concentration. The internal friction of KCl–SrCl2 had an amplitude-independent part. The stress decrement at the onset of increasing internal friction was independent of the SrCl2 concentration. The amplitude-dependent internal friction of KCl–KBr and KCl–KI consisted of a part that was due to the impurity, and a part that was due to forest dislocations. The amplitude-dependent internal friction of KCl–SrCl2 was due only to forest dislocations.

Amplitude Dependent Internal Friction during Plastic Deformation of KCl Doped with KBr, KI or SrCl2. T.Ohgaku, Y.Hasegawa: Journal of Materials Science, 2001, 36[15], 3617-22