ISSN:
1662-9752
Source:
Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
Topics:
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
Notes:
Modelling hot flow stress during grain refinement operations of fcc metals has largelyincluded the use of an Avrami type equation to describe the decrease in stress due to DynamicRecrystallization (DRX). However when refining large-grained copper, the processing temperaturesand strain rates often produce a multi peak behaviour, which is not predictable by an Avramiequation alone. If an initial grain size, D0, is greater than the stable dynamically recrystallized grainsize, Drex, which is a function of the Zener-Hollomon Parameter, Z, then the material will tend torefine. However if the current the Zener-Hollomon value, given by current temperature and strainrate conditions, is lower than a critical value, Zc, which depends on D0, then a multi peak stressbehaviour is expected while refining. The latter Relative-Grain-Size model (i.e. the D0-Zc and Drex-Zrelationships plotted on the same log-log graph) is a practical model that allows determination ofwhether a material will grain coarsen or refine and whether the dynamic recrystallization behaviourwill be monotonic or with multi peaks. The present authors devised a dynamic recrystallizationalgorithm to measure the stress due to the diminishing initial grain volume and to measure thecorrection stress due to recrystallizing grains. Analysis on the hot (600ºC-950ºC) compression dataof a 99.9% pure copper inductively lead to the use of an Avrami type equation to describe the stresscontribution produced by the deformation of the remaining initial grain volume and a dampedcosine equation to describe the stress contribution of the synchronized volume of new grains. Thiswork discusses the experimental evidence and analytical findings that inductively support themathematical description of the stress-strain curve given by a Damped Cosine Avrami Model fordiscontinuous DRX
Type of Medium:
Electronic Resource
URL:
http://www.tib-hannover.de/fulltexts/2011/0528/02/16/transtech_doi~10.4028%252Fwww.scientific.net%252FMSF.550.565.pdf
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