Size effect on mechanical properties in high-order hierarchically nanotwinned metals
- PDF / 1,141,521 Bytes
- 17 Pages / 584.957 x 782.986 pts Page_size
- 50 Downloads / 166 Views
Size effect on mechanical properties in high-order hierarchically nanotwinned metals Jicheng Li1 Ke-Gang Wang2,a) 1
Department of Mechanical & Civil Engineering, Florida Institute of Technology, Melbourne, Florida 32901, USA; Institute of Systems Engineering, China Academy of Engineering Physics, Mianyang, Sichuan 621999, China; and Shock and Vibration of Engineering Materials and Structures Key Laboratory of Sichuan Province, Mianyang, Sichuan 621999, China 2 Department of Mechanical & Civil Engineering, Florida Institute of Technology, Melbourne, Florida 32901, USA a) Address all correspondence to this author. e-mail: kwang@fit.edu Received: 17 August 2018; accepted: 3 October 2018
Theoretical models for the strength and ductility of high-order hierarchically nanotwinned metals are developed, and especially analytical expressions of mechanical parameters with various influencing factors are deduced. Furthermore, the size effect on mechanical properties is analyzed based on these mechanism-based plasticity models, wherein the effects of twin spacing and grain size on the strength and ductility are discussed systemically. Related analysis demonstrates that the twin spacing plays an important role. Through adjusting the twin spacing of the primary layer of twin lamellae and optimizing the combination of twin spacing of the high-order layers, expected mechanical properties with high strength and high ductility could be achieved. Besides, the grain size also has a significant effect, and the reduction in grain size still induces a positive effect on the strength, whereas a negative effect on the ductility. Finally, a material design approach for the optimization of comprehensive mechanical properties is suggested.
Introduction Improving comprehensive mechanical properties is always a central objective of materials research. However, traditional approaches for strengthening materials usually compromise their ductility. Regarding to metallic materials, benefit from the grain boundary (GB) strengthening effect, grain refinement can increase the amount of GBs and further enhance the strength of metals. This is just the so-called Hall–Petch effect [1, 2]. Consequently, nanocrystalline metals attracted extensive investigations [3, 4, 5, 6, 7, 8]. Unfortunately, the ductility of nanocrystalline metals with high strength becomes very limited, i.e., the strength–ductility trade-off dilemma still cannot be evaded. The low ductility of nanocrystalline materials is mainly derived from the deformation and premature failure in interfaces within the material; thus, this shortcoming could be overcome by tuning the interfacial structures or properties. Such effort is usually called as interfacial engineering [7]. Among all possible boundary structures, twin boundary (TB) stands out for its capability to enhance strength and retain ductility of crystalline metals [7, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18]. TBs play a strengthening role like other kinds of boundary
ª Materials Research Society 2019
structures, and they interact with dis
Data Loading...
