Effect of Sn Addition in Preprecipitation Stage in Al-Cu Alloys: A Correlative Transmission Electron Microscopy and Atom
- PDF / 1,876,548 Bytes
- 11 Pages / 593.972 x 792 pts Page_size
- 48 Downloads / 182 Views
RODUCTION
THE microalloying effect in various Al alloys has been well documented since the 1950s.[1–8] The influence of the microalloying elements on material systems has previously been investigated extensively by means of X-ray techniques, transmission electron microscopy (TEM), high-angle annular dark-field scanning TEM, and atom probe field ion microscopy.[9–24] In the case of age hardenable Al-Cu systems, Sn, Cd, and In are key microalloying elements.[4,5] These alloys exhibit much superior strengths and/or hardness in comparison to the binary alloy. However, the origins behind the effects of the microalloying addition remain intriguing. It has been shown that the heterogeneous nucleation of h¢ phases on precursor Sn precipitates (b-Sn) occurs in the Al-Cu-Sn ternary system, leading to a high number density of h¢ phases.[14,17,18] Notably, Bourgeois et al.[9,24] provided careful TEM experiments in recent years and identified a variety of orientations and interfacial TOMOYUKI HOMMA, Assistant Professor, formerly with the Australian Key Centre for Microscopy & Microanalysis, The University of Sydney, Sydney, NSW 2006, Australia, is now with the Department of Mechanical Engineering, Nagaoka University of Technology, Nagaoka, 940-2188 Japan. Contact e-mail: thonma@ mech.nagaokaut.ac.jp MICHAEL P. MOODY, Lecturer, formerly with the Australian Centre for Microscopy & Microanalysis, The University of Sydney, is now with the Department of Materials at The University of Oxford, Oxford, UK. DAVID W. SAXEY, Research Associate Professor, formerly with the Australian Key Centre for Microscopy & Microanalysis, The University of Sydney, is now with the School of Physics, University of Western Australia, Crawley, WA 6009, Australia. SIMON P. RINGER, Director and Professor, is with the Australian Centre for Microscopy & Microanalysis, The University of Sydney. Manuscript submitted August 18, 2011. Article published online March 21, 2012 2192—VOLUME 43A, JULY 2012
reactions between the Sn and the h¢. However, investigations into the effect of the microalloying addition on the atomic clustering in preprecipitation stages have been more limited. The atomic clustering of microalloying solutes is now recognized as an important stage of microstructure evolution within aged materials. Experimental investigations into the evolution of nanoscale microstructures in Al alloys using atom probe tomography (APT), TEM, and positron-annihilation techniques[25–30] have demonstrated the paths fine-scale solute–solute interactions present for the formation of larger precipitates and phases. Furthermore, the proposal that the initial finescale clustering can influence mechanical properties significantly has been confirmed independently.[27,31] In this contribution, we focus on the processes involved in the decomposition of the solid solution in a base Al-1.7Cu (at. pct) alloy and one containing 0.01 at. pct Sn during increased temperature aging at 473 K (200 C) using a combination of APT and TEM. In particular, APT has emerged as a powerful technique for th
Data Loading...
