INTERNAL STRESS AND HIGH TEMPERATURE CREEP MECHANISM IN ORDERED AND DISORDERED BETA BRASS SOLID SOLUTION ALLOYS (DISLOCATION, MICROCREEP, TRANSIENT)

The high temperature creep behavior and creep transient behavior after strain transient dip test were investigated in ordered and disordered beta brass solid solution alloys. The controlling creep mechanism was investigated by considering several factors proposed as the criteria for determining the controlling creep mechanism in solid solution alloys. The stress and temperature dependence of internal stress was investigated and compared with Weertman's theory of internal stress.;The stress and temperature dependence of internal stress in ordered and disordered beta brass was found to agree well with Weertman's theory. Correlating the internal stress measurements with the theory, the friction stress is estimated to be larger in ordered beta brass than in disordered beta brass. The larger internal stress in ordered beta brass is considered to be from the larger friction stress. The modified power-law creep exponents with friction stress were measured as 3.0 in both ordered and disordered beta brass as predicted by Weertman's theory.;Comparing the friction stress with the critical stresses for microcreep mechanisms, the friction stress is considered to be from the stress-induced order mechanism in ordered and disordered beta brass. Comparing the drag constants for microcreep mechanisms, the Cottrell-Jaswon mechanism and the antiphase boundary mechanism are considered to control the viscous glide of dislocations in ordered beta brass. In disordered beta brass, the Cottrell-Jaswon mechanism is considered to control the viscous glide of dislocations.;There is no detectable primary creep stage in ordered beta brass, although brief inverted primary creep stage was observed in disordered beta brass. The power-law creep exponents were measured as 3.5 for ordered beta brass and 3.2 for disordered beta brass. The instantaneous elongation and instantaneous contraction are in good agreement for a given stress change in ordered and disordered beta brass. The dislocations observed in crept ordered beta brass show the smoothly curved shapes with random distributions. From these investigated factors, the ordered and disordered beta brass are classified as class I alloys and the dislocation glide process is considered as the controlling creep mechanism.