High-Strength Nanotwinned Al Alloys with 9R Phase
Qiang Li, School of Materials Engineering, Purdue University, West Lafayette, IN, 47907, USA.
Sichuang Xue, School of Materials Engineering, Purdue University, West Lafayette, IN, 47907, USA.
Jian Wang, Mechanical and Materials Engineering, University of Nebraska-Lincoln, Lincoln, NE, 68588, USA.
Shuai Shao, Mechanical and Industrial Engineering, Louisiana State University, Baton Rouge, LA, 70803, USA.
Anthony H. Kwong, Division of Engineering and Applied Science, California Institute of Technology, Pasadena, CA, 91125, USA.
Adenike Giwa, Division of Engineering and Applied Science, California Institute of Technology, Pasadena, CA, 91125, USA.
Zhe Fan, Oak Ridge National Laboratory, Oak Ridge, TN, 37830, USA.
Yue Liu, State Key Lab of Metal Matrix Composites, School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai, 200240, P. R. China.
Zhimin Qi, School of Materials Engineering, Purdue University, West Lafayette, IN, 47907, USA.
Jie Ding, School of Materials Engineering, Purdue University, West Lafayette, IN, 47907, USA.
Han Wang, School of Materials Engineering, Purdue University, West Lafayette, IN, 47907, USA.
Julia R. Greer, Division of Engineering and Applied Science, California Institute of Technology, Pasadena, CA, 91125, USA.
Haiyan Wang, School of Materials Engineering, Purdue University, West Lafayette, IN, 47907, USA.
Xinghang Zhang, School of Materials Engineering, Purdue University, West Lafayette, IN, 47907, USA.
Abstract
Light-weight aluminum (Al) alloys have widespread applications. However, most Al alloys have inherently low mechanical strength. Nanotwins can induce high strength and ductility in metallic materials. Yet, introducing high-density growth twins into Al remains difficult due to its ultrahigh stacking-fault energy. In this study, it is shown that incorporating merely several atomic percent of Fe solutes into Al enables the formation of nanotwinned (nt) columnar grains with high-density 9R phase in Al(Fe) solid solutions. The nt Al-Fe alloy coatings reach a maximum hardness of ≈5.5 GPa, one of the strongest binary Al alloys ever created. In situ uniaxial compressions show that the nt Al-Fe alloys populated with 9R phase have flow stress exceeding 1.5 GPa, comparable to high-strength steels. Molecular dynamics simulations reveal that high strength and hardening ability of Al-Fe alloys arise mainly from the high-density 9R phase and nanoscale grain sizes.
