A debris mechanism of cyclic strain hardening for F.C.C. metals

Abstract Prismatic dislocation loops (dislocation debris), formed by fatigue or cyclic straining, have been observed in a number of metals. To account for these observations a mechanism of cyclic strain hardening is proposed which depends on the ease of loop formation and the behaviour of the loops after they are formed. In the initial rapid hardening stage, the rate of cyclic strain hardening is determined by the rate of formation of debris obstacles. Since the debris is thought to be formed by some variant of the double cross slip mecachism, changes of variable which lead to easier cross-slip result in higher hardening rates (because the rate of debris obstacle formation is increased). As the crystal fills up with debris, the motion of screw dislocations diminishes and the enforced strain is accommodated by the motion of the prismatic loops already present in the crystal. The basic motion of the prismatic dislocation loops is a flip-flop motion from one stable equilibrium position to another which is re...

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