Effect of strain rate on microstructure of polycrystalline oxygen-free high conductivity copper severely deformed at liquid nitrogen temperature

Abstract

Phenomenological plastic flow stress models are used extensively in the simulation of large deformations of metals at high strain-rates and high temperatures. Several such models exist and it is difficult to determine the applicability of any single model to the particular problem at hand. Ideally, the models are based on the underlying (subgrid) physics and therefore do not need to be recalibrated for every regime of application. In this work we compare the Johnson-Cook, Steinberg-Cochran-Guinan-Lund, Zerilli-Armstrong, Mechanical Threshold Stress, and Preston-Tonks-Wallace plasticity models. We use OFHC copper as the comparison material because it is well characterized. First, we determine parameters for the specific heat model, the equation of state, shear modulus models, and melt temperature models. These models are evaluated and their range of applicability is identified. We then compare the flow stresses predicted by the five flow stress models with experimental data for annealed OFHC copper and quantify modeling errors. Next, Taylor impact tests are simulated, comparison metrics are identified, and the flow stress models are evaluated on the basis of these metrics. The material point method is used for these computations. We observe that the all the models are quite accurate at low temperatures and any of these models could be used in simulations. However, at high temperatures and under high-strain-rate conditions, their accuracy can vary significantly.

Hydrostatic pressure effects on deformation mechanisms of nanocrystalline fcc metals

“…7, partial dislocation behaviors, formation of SFs and formation of dislocation networks are all enhanced with increasing hydrostatic pressure when the grain size is large (15 nm), which is consistent with results shown in GB thickening is observed to increase monotonically with increasing hydrostatic pressure for both grain sizes, and the NC Cu with grain size of 3 nm has the trend to become amorphous state after 10% strain compression when the hydrostatic pressure is as high as 80 GPa. The crystalline-to-amorphous transition has generally been observed during the high-strain-rate deformation processes [36][37][38]. Meyers et al [36] reported the first observation on crystalline-to-amorphous transition in stainless steel inside a shear band formed under dynamics loading, which was attributed to a non-equilibrium solid-state amorphization process rather than melting.…”

Bi-modal Structure of Copper via Room-Temperature Partial Recrystallization After Cryogenic Dynamic Compression

“…[33,34] These two features enable twin boundaries to exist (even at high temperature) after deformation and enable the materials to have great strength. [6] High speed and low temperature (over~33 of ln Z) are required for twinning to be activated as one of the main deformation mechanisms in copper, and the twin fraction increases with increasing ln Z. [7,8] Thus, the CTD sample with~64 of ln Z could have many twin boundaries.…”

“…To understand the effect of the Z parameter at not only extreme but also ordinary conditions, the deformation of copper over a wide range of temperature and strain rate were studied. [6][7][8] However, these studies have three deficiencies: (1) few study at strain rates over~10 3 s À1 and at cryogenic temperature, (2) less consideration for global microstructural features than for local microstructural ones, and (3) insufficient attention to reheating from cryogenic temperature to room temperature after the deformation.…”

“…In order to further decrease the lower bound of the grain size, and to expand the microstructural window of SPD-processed materials, many researchers have been interested in controlling processing parameters, such as strain rate and temperature, at extreme levels. [6][7][8][9][10] The simultaneous effects of strain rate and temperature on microstructural evolution during plastic deformation are generally expressed by the Zener-Hollomon parameter, Z, as follows:…”

Study on Surface Asperity Flattening in Cold Quasi-Static Uniaxial Planar Compression by Crystal Plasticity Finite Element Method

“…They found that the increase in strain rate causes increase in strain hardening which thereby influences the texture. Zhang et al [10] studied the effect of strain rate on microstructure of polycrystalline oxygen-free high conductivity copper severely deformed at liquid nitrogen temperature. Kodeeswaran et al [11] analysed the effect of strain rate on nanocrystalline surface formation in controlled ball impact process in AISI 304 SS.…”