Atomistic mechanisms of fatigue in nanotwinned metals. (15th October 2015)

• Record Type: Journal Article
• Authors: Zhou, Xiaoling; Li, Xiaoyan; Chen, Changqing
• Is Part Of: Acta materialia. Volume 99(2015)
• Page Start: 77
• Page End: 86
• Publication Date: 2015-10-15
• Subjects: Fatigue crack -- Nanoscale twins -- Dislocation -- Detwinning -- Atomistic simulation; Materials -- Periodicals; Materials science -- Periodicals; Materials -- Mechanical properties -- Periodicals; Metallurgy -- Periodicals; Chemistry, Inorganic -- Periodicals; 620.112
• DOI: 10.1016/j.actamat.2015.07.045
• Languages: English
• ISSNs: 1359-6454

Abstract

Graphical abstract: Abstract: We investigate the fatigue behavior of nanotwinned Cu using a combination of molecular statics and molecular dynamics simulations. The presence of nanoscale twins is found to enhance fatigue crack growth resistance. For the twin-free nanocrystalline samples, the fatigue crack propagates by linking the nanovoids that are formed ahead of the crack tip. In the case of the nanotwinned samples, however, it advances as the crack tip alternately blunts and re-sharpens due to dislocation emission and slip. Both detwinning and crack closure are observed in the path of the fatigue crack in nanotwinned samples with a high density of twin boundaries. As the twin number per grain (quantified by the ratio of the mean grain size to the twin boundary spacing d / λ ) increases, detwinning increases the dissipated energy of fatigue cracking, leading to enhanced fatigue resistance. The atomistic simulations show that fatigue crack growth in nanotwinned Cu conforms to Paris' law. In conjunction with the experimental results, we obtain a quantitative estimation of the Paris' law exponent (∼4.0), which is in agreement with the theoretical predictions from the damage accumulation model.