Abstract
Atomic force microscopy (AFM) measurements of dihedral angles are conducted for the first time to characterize the ratio of the twin-boundary energy (γΤ) to the surface free energy (γS). In plane, twin morphology is measured with AFM, verified by scanning electron microscopy, optical microscopy, and found to be consistent. The chemical composition and homogeneity of annealed Cu10 wt%Zn sample are confirmed by energy-dispersive spectroscopy. AFM data indicate that the average depth and height of the grooves and peaks are 118 ± 45 and 158 ± 45 nm, respectively. Surface roughness parameters, Sq and Sa, are measured by a factor of two to four less than the depth and height of the twin boundaries. Both surface roughness parameters are less with no planar defects present compared with selected areas containing twin boundaries. The average dihedral angle is found to be 167 ± 5° for the grooves and 193 ± 4° for the peaks. The twin to surface interfacial free energy ratio, γT/γS, is 0.0018. The comparison of AFM-based results to the other method-based results obtained on pure metals is discussed.
Highlights
Knowledge of interfacial energy values may be necessary when solving microstructural or metallurgical challenges in demanding the industrial applications of commercial CuZn alloys where the combinations of strength, machinability, and corrosion resistance are required (Zhao et al, 2007; Zhang et al, 2008; Igelegbai et al, 2017; Choucri et al, 2019; Gu et al, 2019; Zaynullina et al, 2019)
The opening width for boundaries is found to be ∼1 μm based on Atomic force microscopy (AFM) measurements, which is greater than scanning electron microscopy (SEM) estimates of ∼0.5 μm
AFM has been proven for the first time to be a feasible new method for measuring the dihedral angles of twin-boundary grooves
Summary
Knowledge of interfacial energy values may be necessary when solving microstructural or metallurgical challenges in demanding the industrial applications of commercial CuZn alloys where the combinations of strength, machinability, and corrosion resistance are required (Zhao et al, 2007; Zhang et al, 2008; Igelegbai et al, 2017; Choucri et al, 2019; Gu et al, 2019; Zaynullina et al, 2019). Nucleation, growth, and coarsening of precipitates (Lifshitz & Slezov, 1961; Wagner, 1961) or grain growth, mobility, and recrystallization (Shockley & Read, 1949; Herring, 1951) are at the heart of end-user mechanical properties such as hardness, strength, and ductility. Knowledge of the optimal stacking fault energy has been reported as a key factor in achieving higher ductility in ultrafinegrained CuZn alloys (Zhao et al, 2007). There is a close association between interfacial free energy and interfacial composition gT gS
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