@article{setman_kerber_bahmanpour_horky_scattergood_koch_zehetbauer_2013, title={Nature and density of lattice defects in ball milled nanostructured copper}, volume={67}, ISSN={["1872-7743"]}, DOI={10.1016/j.mechmat.2013.07.007}, abstractNote={Copper powder of 99.9% purity with particle size in the micrometer range was subjected to high energy ball milling by milling times between 2 and 24 h applying stearic acid as surfactant. The nature and density of lattice defects were determined using differential scanning calorimetry (DSC) and X-ray line profile analysis (XPA). The DSC measurements exhibit a considerable drop of the total stored energy with increasing ball milling time indicating a surprising decrease of lattice defect concentrations by more than one order of magnitude. The results from XPA, however, show that neither the dislocation density, nor the crystallite size can account for this behavior. Rather it is to be attributed to a high concentration of deformation induced vacancy type defects, with their density gradually decreasing during ongoing milling.}, journal={MECHANICS OF MATERIALS}, author={Setman, D. and Kerber, M. and Bahmanpour, H. and Horky, J. and Scattergood, R. O. and Koch, C. C. and Zehetbauer, M. J.}, year={2013}, month={Dec}, pages={59–64} }
 @article{bahmanpour_youssef_horky_setman_atwater_zehetbauer_scattergood_koch_2012, title={Deformation twins and related softening behavior in nanocrystalline Cu-30% Zn alloy}, volume={60}, ISSN={["1873-2453"]}, DOI={10.1016/j.actamat.2012.02.036}, abstractNote={Nanocrystalline Cu–30% Zn samples were produced by high energy ball milling at 77 K and room temperature. Cryomilled flakes were further processed by ultrahigh strain high pressure torsion (HPT) or room temperature milling to produce bulk artifact-free samples. Deformation-induced grain growth and a reduction in twin probability were observed in HPT consolidated samples. Investigations of the mechanical properties by hardness measurements and tensile tests revealed that at small grain sizes of less than ∼35 nm Cu–30% Zn deviates from the classical Hall–Petch relation and the strength of nanocrsytalline Cu–30% Zn is comparable with that of nanocrystalline pure copper. High resolution transmission electron microscopy studies show a high density of finely spaced deformation nanotwins, formed due to the low stacking fault energy of 14 mJ m–2 and low temperature severe plastic deformation. Possible softening mechanisms proposed in the literature for nanotwin copper are addressed and the twin-related softening behavior in nanotwinned Cu is extended to the Cu–30% Zn alloy based on detwinning mechanisms.}, number={8}, journal={ACTA MATERIALIA}, author={Bahmanpour, Hamed and Youssef, Khaled M. and Horky, Jelena and Setman, Daria and Atwater, Mark A. and Zehetbauer, Michael J. and Scattergood, Ronald O. and Koch, Carl C.}, year={2012}, month={May}, pages={3340–3349} }
 @article{atwater_bahmanpour_scattergood_koch_2013, title={The thermal stability of nanocrystalline cartridge brass and the effect of zirconium additions}, volume={48}, ISSN={["0022-2461"]}, DOI={10.1007/s10853-012-6731-5}, number={1}, journal={JOURNAL OF MATERIALS SCIENCE}, author={Atwater, Mark A. and Bahmanpour, Hamed and Scattergood, Ronald O. and Koch, Carl C.}, year={2013}, month={Jan}, pages={220–226} }
 @article{bahmanpour_kauffmann_khoshkhoo_youssef_mula_freudenberger_eckert_scattergood_koch_2011, title={Effect of stacking fault energy on deformation behavior of cryo-rolled copper and copper alloys}, volume={529}, ISSN={["1873-4936"]}, DOI={10.1016/j.msea.2011.09.022}, abstractNote={Abstract Pure copper and Cu–12.1 at.%Al–4.1 at.%Zn alloy were subjected to rolling in liquid nitrogen. TEM studies showed that dynamic recovery during the deformation process was effectively suppressed and hence microstructures with dislocation substructure and deformation twins were formed. Mechanical properties were assessed via microtensile testing that shows improved yield strength, 520 ± 20 MPa, and ductility, 22%, in the case of pure copper. Alloying with Al and Zn results in reduction in stacking fault energy (SFE) which can contribute to enhanced strength and good ductility. Physical activation volume obtained via stress relaxation tests is 26 b 3 , and 8 b 3 for pure copper, and Cu–12.1 at.%Al–4.1 at.%Zn, respectively. The effect of SFE on work hardening rate of samples is discussed. Although twinning is observed in the alloy, it is concluded that network dislocation strengthening plays the major role in determining the mechanical properties.}, journal={MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING}, author={Bahmanpour, H. and Kauffmann, A. and Khoshkhoo, M. S. and Youssef, K. M. and Mula, S. and Freudenberger, J. and Eckert, J. and Scattergood, R. O. and Koch, C. C.}, year={2011}, month={Nov}, pages={230–236} }
 @article{youssef_sakaliyska_bahmanpour_scattergood_koch_2011, title={Effect of stacking fault energy on mechanical behavior of bulk nanocrystalline Cu and Cu alloys}, volume={59}, ISSN={["1873-2453"]}, DOI={10.1016/j.actamat.2011.05.052}, abstractNote={Twinning and dislocation slip are two major and competing modes of plastic deformation in metals and alloys. In addition to controlling the dislocation substructure in coarse grained materials, stacking fault energy (SFE) also affects the propensity to form deformation twins. However, the influence of SFE has not been fully explored in nanocrystalline materials. Here the role of SFE in deformation twinning and work hardening was systematically studied in bulk artifact-free, nanocrystalline (nc) Cu (SFE 55 mJ m−2), and a nc Cu–12.1 at.% Al–4.1 at.% Zn alloy (SFE 7 mJ m−2). The nc Cu (23 nm) and nc Cu alloy (22 nm) were synthesized using in situ consolidation during cryo and room temperature milling. Both materials showed ultra-high tensile strength, significant strain hardening, and good ductility. The nc Cu alloy exhibits a higher yield strength and lower uniform elongation (1067 ± 20 MPa, 6.5%) than that of nc Cu (790 ± 12 MPa, 14%). The SFE variation played a significant role in strengthening the nc Cu alloy. High resolution transmission electron microscopy analyses revealed that the low SFE of the nc Cu alloy alters the deformation mechanism from a dislocation-controlled deformation, which allows for the higher strain hardening observed in the nc Cu, to a twin-controlled deformation.}, number={14}, journal={ACTA MATERIALIA}, author={Youssef, Khaled and Sakaliyska, Miroslava and Bahmanpour, Hamed and Scattergood, Ronald and Koch, Carl}, year={2011}, month={Aug}, pages={5758–5764} }
 @article{bahmanpour_youssef_scattergood_koch_2011, title={Mechanical behavior of bulk nanocrystalline copper alloys produced by high energy ball milling}, volume={46}, ISSN={["1573-4803"]}, DOI={10.1007/s10853-011-5312-3}, number={19}, journal={JOURNAL OF MATERIALS SCIENCE}, author={Bahmanpour, H. and Youssef, K. M. and Scattergood, R. O. and Koch, C. C.}, year={2011}, month={Oct}, pages={6316–6322} }