Serrated plastic flow

This paper attempts an assessment of the current understanding of the phenomenon of “serrated plastic flow”, which manifests itself as serrations, load drops, jerkiness or other discontinuities in the stress-strain curves obtained in constant extension rate tensile tests, and as sudden bursts of strain in constant loading rate tests and in constant load (stress) creep tests (the so called staircase creep). Though one can identify at least seven physical processes that can cause serrations, the discussion here is restricted mainly to serrated yielding in tension tests originating from dynamic strain ageing (dsa). The characteristics of the five types of serrations that have been identified so far and the experimental conditions under which they occur are discussed. The various models of serrated flow that have been put forward are reviewed critically. Some recent results on 316 stainless steel are presented to illustrate the effects of grain size, temperature and strain rate on serrated flow. Manifestations ofdsa other than serrations such as a negative strain rate sensitivity, positive temperature dependence for flow stress and work hardening, and the ductility minimum are also discussed. Finally the various issues to be resolved are enumerated.

[1]  B. A. Wilcox,et al.  On serrated yielding and negative strain-rate sensitivity , 1966 .

[2]  S. Mannan,et al.  Strain-ageing in disordered CuAu , 1972 .

[3]  G. Bolling,et al.  Continual mechanical twinning: Part I: Formal description , 1965 .

[4]  Y. Estrin,et al.  Computer simulation of the low temperature instability of plastic flow , 1982 .

[5]  A. van den Beukel,et al.  Theory of the effect of dynamic strain aging on mechanical properties , 1975 .

[6]  G. A. Malygin.  Dynamic interaction of impurity atmospheres with moving dislocations during serrated flow , 1973 .

[7]  H. G. Bueren.  Theory of the formation of lattice defects during plastic strain , 1955 .

[8]  S. Bodner,et al.  Discontinuous yielding of commercially-pure aluminium , 1967 .

[9]  A. Cottrell,et al.  LXXXVI. A note on the Portevin-Le Chatelier effect , 1953 .

[10]  U. F. Kocks,et al.  The strain dependence of static and dynamic strain-aging , 1982 .

[11]  G. Venkataraman,et al.  Instability associated with repeated yield drop , 1983 .

[12]  S. Bodner,et al.  Repeated discontinuous yielding of 2024 aluminum alloy , 1969 .

[13]  S. K. Ray,et al.  Dynamic strain ageing in type 316 stainless steel at 300 K , 1992 .

[14]  R. Reed-hill,et al.  Dynamic strain aging and ductility minima in zirconium , 1970 .

[15]  S. Morozumi,et al.  A Portevin-Le Chatelier Effect expected from Solute Atmosphere Dragging , 1971 .

[16]  P. Penning.  Mathematics of the portevin-le chatelier effect , 1972 .

[17]  E. Pink,et al.  Serrated flow in a ferritic stainless steel , 1981 .

[18]  A. Sleeswyk.  Slow strain-hardening of ingot iron , 1958 .

[19]  W. C. Leslie,et al.  Some aspects of serrated yielding in substitutional solid solutions of iron , 1972 .

[20]  U. F. Kocks,et al.  New observations on the mechanisms of dynamic strain aging and of jerky flow , 1979 .

[21]  J. V. Westrum,et al.  A new type of stress-strain curve and the Portevin-Le Chatelier effect in Au (14 at.% Cu) , 1972 .

[22]  J. Barber.  XXXVII. On preventing the freezing of water in pipes , 1804 .

[23]  B. Russell,et al.  Repeated yielding in tin bronze alloys , 1963 .

[24]  Frank Reginald Nunes Nabarro,et al.  Theory of crystal dislocations , 1967 .

[25]  J. Weertman.  Theory of Infinitesimal Dislocations Distributed on a Plane Applied to Discontinuous Yield Phenomena , 1967 .

[26]  P. G McCormigk,et al.  A model for the Portevin-Le Chatelier effect in substitutional alloys , 1972 .

[27]  V. Seetharaman.  Deformation and martensitic transformation , 1984 .

[28]  W. Tegart,et al.  Serrated flow in gold-indium alloys , 1969 .

[29]  C. G. Schmidt,et al.  The effect of solutes on the strength and strain hardening behavior of alloys , 1982 .

[30]  A. V. D. Beukel.  On the mechanism of serrated yielding and dynamic strain ageing , 1980 .

[31]  William Charnock,et al.  The apparent activation energy for serrated yielding , 1969 .

[32]  W. Charnock.  The influence of grain size on the nature of portevin-lechatelier yielding , 1968 .