Effect of thermal stress upon internal friction in Mg-Se alloys

Internal friction of Mg-Se alloys has been studied after sequential thermal treating. The obtained strain amplitude dependences of the logarithmic dec rement can be divided into two regions. In the region of small strain ampli tudes the decrement is dependent on the amplitude only slightly while at hi gher amplitudes the decrement depends strongly on the amplitude. Both regio ns are separated by a critical strain amplitude. The thermal treatment of a lloys changes the sample microstructure. These changes are reflected in the dependence of the critical amplitude on the thermal treatment temperature. An increase of the critical amplitude with temperature up to 160 degrees C is interpreted on the base of the theory of vibration of short and long di slocation segments caused by a sonic wave. Solving of Sc clusters (up to ap proximate to 160 degrees C) is very probably followed at higher temperature s by a precipitation process.