The Influence of Growth Rate on Mechanical and Thermodynamical Properties of the Zn-Ti0.075-Cu0.15 Single Crystals Deformed at (0001)<11-20> System

Abstract

The single crystals were produced from industry zinc alloy containing 0.075wt.% of titanium and 0.15wt.% of copper. The Bridgman method was applied to obtain the single crystal. Three growth rates were used: 6mm/h, 10mm/h and 16mm/h. The common feature of all of the produced single crystals was homogeneous distribution of the second phase on a sections normal to the growth direction. The investigated single crystals were deformed in compression test with jump changes of the strain rate (from 10-4s-1 on 10-3s-1). From the obtained stress-strain curves the Critical Resolved Shear Stress (CRSS), hardening coefficient in the easy slip range (QA) and thermodynamical – activation volume (V*) and activation enthalpy (DH) were determined. The tests were done at the temperature range from 77K to 400K. Results showed anomaly on the CRSS=f(T) curve. The temperature of an extreme was 240K. The same effect was observed on V*=f(T) and DH=f(T) curves. The presented results reveal good correlation with crack phenomena that was observed during a bent of the zinc alloy sheets at the temperatures below 300K.