Portevin-Le-Chatelier effect

It has been shown that several polymers exhibit instabilities in their plastic deformation process. It should finally be mentioned that instabilities may also occur during the plastic deformation of metals This phenomenon which is called the Portevin-Le Chatelier effect, is generally interpreted in terms of different modes of dislocation movement depending on whether or not dislocations move by dragging along their atmosphere of impurities behind them. 

The Portevin-Le Chatelier effect with serrated yielding was observed for both the ordered and disordered state (Mohamed etal., 1974). Recovery and recrystallization have been analyzed in detail (Vidoz etal., 1963 Cahn, 1990, 1991). Experimental and theoretical studies have been directed at dislocations and antiphase domain boundaries (see, e.g. Tichelaar and Schapink, 1991 D. G. Morris, 1992 Veyssiere, 1992), grain boundaries (Yan etal., 1992), and the electronic structure (Bose et al., 1991). It is noted that disordered layers are formed in ordered CujAu on antiphase boundaries and twin boundaries just below the order-disorder transition temperature (Tichelaar et al., 1992). This may be expected in other phases, too, and may improve the ductility of less ductile phases, as is discussed for NijAl (see Sec. 4.1.2). 

Although Y ions present only weak obstacles to dislocation motion [58], they are present in high concentrations and could, in theory, yield a large contribution to the flow stress. However, the crystals presently available apparently contain very small precipitates of ZrN [71] which provide stronger obstacles to slip than do unassociated Y ions [58, 72, 73]. Nonetheless, these unassociated Y ions do cause plastic instabilities, such as dynamic strain aging or the Portevin-Le Chatelier effect in... 

Cie] observed Portevin-Le Chatelier Effect in biaxially strained Al-Fe-Si foils. This effect is attributed to the diffusion of Si rather than Fe, as the latter has much slower diffusivity and low solubiUty in (Al). [2003Mur] reported the hardness and indentation fracture toughness of T2 and T5 phases, both have hardness much higher than binary aluminides and they have very similar indentation fracture toughness. 

Cie] Cieslar, M. C., Fressengeas, C., Karimi, A., Martin, J.L., Portevin-Le Chatelier Effect in Biaxially Strained Al-Fe-Si Foils , Scr. Mater., 48, 1105-1110 (2003) (Experimental, Meehan. Prop., 19)... 

Fig. 4.55 The Portevin-Le Chatelier (PLC) effect. The influence of temperature on the appearance of a stress-strain curve under tension [7]...

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