0.5 46 2 0.47 43 47 0.28 12 16 0.44 47 37 (only system observed for 200 nm diam. pillars) 0.42 47 40 Ill-defined slip traces 18 33 0.3 18 21 Ill-defined slip traces 0.5 48 1 Stress-strain response Stress-strain behavior of representative compression pillars with diameters β-CuZn ranging from 5 µm to 200 nm are shown in Figure 5.5 as a function of crystal orientation. These stress-strain curves have distinctive features typical of micropillar deformation. During the initial loading (well under 1% strain), relatively low and inconsistent stiffness values are recorded. This is thought to be caused by pillar surface features and initial seating of the indenter on the pillar [87]. Quickly the stiffness increases and the pillar undergoes elastic loading, until a critical point is reached and strain increases sharply under a constant applied load. Interestingly, such strain bursts remained prevalent for relatively large diameters. This is in contrast with previous studies on various FCC and BCC metals that have shown decreasing strain bursts for pillar diameters of 2 µm or larger [6,7,84,97,135]. Nevertheless, bulk deformation of has demonstrated or flow stress, somewhat β-CuZn ‘jerky’ ‘serrated’ resembling the strain bursts observed in micropillar testing [48,49]. Figure .: Representative stress-strain behavior of compression pillars. The curves fundamentally β-CuZn change shape with decreasing diameter. Figure 5.6a shows the critical resolved shear stress (CRSS) values at 2.5% strain for all samples tested. A 2.5% strain value was chosen because it is beyond the first observed strain burst, yet still low enough to be minimally affected by strain hardening. Although
(only system observed for 200 nm diam. pillars) 0.5 0.47 0.28 0.44 0.42 46 43 12 47 47 2 47 16 37 40 Ill-defined slip traces 0.3 18 18 33 21 Ill-defined slip traces 0.5 48 1 Stress-strain response Stress-strain behavior of representative β-CuZn compression pillars with diameters ranging from 5 µm to 200 nm are shown in Figure 5.5 as a function of crystal orientation. These stress-strain curves have distinctive features typical of micropillar deformation. During the initial loading (well under 1% strain), relatively low and inconsistent stiffness values are recorded. This is thought to be caused by pillar surface features and initial seating of the indenter on the pillar [87]. Quickly the stiffness increases and the pillar undergoes elastic loading, until a critical point is reached and strain increases sharply under a constant applied load. Interestingly, such strain bursts remained prevalent for relatively large diameters. This is in contrast with previous studies on various FCC and BCC metals that have shown decreasing strain bursts for pillar diameters of 2 µm or larger [6,7,84,97,135]. Nevertheless, bulk deformation of β-CuZn has demonstrated ‘jerky’ or ‘serrated’ flow stress, somewhat resembling the strain bursts observed in micropillar testing [48,49]. Figure .: Representative stress-strain behavior of β-CuZn compression pillars. The curves fundamentally change shape with decreasing diameter. Figure 5.6a shows the critical resolved shear stress (CRSS) values at 2.5% strain for all samples tested. A 2.5% strain value was chosen because it is beyond the first observed strain burst, yet still low enough to be minimally affected by strain hardening. Although
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