Size effects and temperature dependence on strain-hardening mechanisms in some face centered cubic materials

作者：Hug E^*; Dubos P A; Keller C; Duchene L; Habraken A M

来源：Mechanics of Materials, 2015, 91: 136-151.

DOI：10.1016/j.mechmat.2015.07.001

• Size effects
• Thermomechanical behavior
• Plasticity
• Face centered cubic materials
• Dislocation substructures
• Strain gradient plasticity model

The mechanical behavior of face centered cubic metals is deeply affected when specimen dimensions decrease from a few millimeters to a few micrometers. At room temperature, a critical thickness (t) to grain size (d) ratio (t/d)(c) was previously highlighted, under which the softening of mechanical properties became very pronounced both in terms of Hall-Petch relation and work hardening mechanisms. In this work, new experimental results are provided concerning the influence of temperature on this size effect for copper, nickel and Ni-20 wt.%Cr, representative of a wide range of deformation mechanisms (i.e. dislocation slip character). It is shown that multicrystalline samples (t/d<(t/d)c) are not deeply affected by an increase in temperature, independently of the planar or wavy character of dislocation glide. For pronounced wavy slip character metals, surface effects in polycrystals (t/d>(t/d)(c)) are not significant enough to reduce the gap between poly-crystal and multicrystal mechanical behavior when the temperature increases. However, a transition from wavy slip to planar glide mechanisms induces a modification of the polycrystalline behavior which tends toward multicrystalline one with a moderate increase in temperature. This work demonstrates that surface effects and grain size influence can be successfully disassociated for the three studied materials using an analysis supported by the Kocks-Mecking formalism. All these results are supported by microscopic investigations of dislocation substructures and compared to numerical simulations using a strain gradient plasticity model.

• 出版日期2015-12