Abstract
Methodical aspects of the determination of contribution to the total strain of all the three mechanisms providing superplastic flow: grain boundary sliding, intragranular dislocation strain and diffusion creep, have been considered in the paper. Experimental measurements have been conducted on the magnesium alloy MA8 (Mg-1.5%Mn-0.3%Ce) and the aluminium alloy AMg6 (Al-6.3%Mg-0.5%Mn) in which it is possible to determine independently the contributions of different mechanisms in Regions I, II and III of superplastic behaviour of these alloys. The obtained data on the contributions of intragranular dislocation strain (γIS) and diffusion creep (γDC) seem to be most reliable. The value of γIS for the investigated alloys is about 20% at the optimum strain rate (Region II), it tends to increase in Region I and rises sharply in Region III. The value of γIS in Region II is equal only to a few percent but it increases to about 20% in Region I. The values of γGBS have been estimated from the results of grain size measuring and according to the method of marker lines offset. They have been also determined from expression γGBS = 1 − γDC−γIS. It has been established that in the latter case the calculated values are close to those obtained from grain shape measuring but are higher than those obtained according to the method of marker lines offset. The results of this study are compared to the data of other investigations.
Published Version
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