An in situ synchrotron X-ray diffraction study of precipitation kinetics in a severely deformed Cu–Ni–Si alloy

• Published in: Materials science & engineering. A, Structural materials : properties, microstructure and processing Structural materials : properties, microstructure and processing, 2014-03, Vol.597, p.288-294
• Main Authors: Azzeddine, H., Mehdi, B., Hennet, L., Thiaudière, D., Alili, B., Kawasaki, M., Bradai, D., Langdon, T.G.
• Format: Article
• Language: English
• Subjects: Aging; AGING MECHANISMS; AGING PARAMETERS; Arrays; Condensed Matter; Condensed matter: structure, mechanical and thermal properties; COPPER ALLOYS (40 TO 99.3 CU); Copper base alloys; Cross-disciplinary physics: materials science; rheology; Cu–Ni–Si alloy; DEFORMATION; Diffraction; ECAP; Equal channel angular pressing; Equations of state, phase equilibria, and phase transitions; Exact sciences and technology; General studies of phase transitions; HPT; KINETICS; Materials Science; Nucleation; Other heat and thermomechanical treatments; Phase diagrams and microstructures developed by solidification and solid-solid phase transformations; Physics; Precipitation; Solid solution, precipitation, and dispersion hardening; aging; Synchrotron X-ray diffraction; Synchrotrons; Treatment of materials and its effects on microstructure and properties; Ultrafine-grained metals; X RAY DIFFRACTION; X RAYS
• ISSN: 0921-5093; 1873-4936
• DOI: 10.1016/j.msea.2013.12.092

In situ synchrotron X-ray diffraction was used to study the decomposition kinetics of a metastable Cu–2.5Ni–0.6Si (wt%) alloy after severe plastic deformation by equal-channel angular pressing (ECAP) and high-pressure torsion (HPT). The measurements were performed at room temperature and also at high temperatures of 723, 823 and 973K in order to determine the ageing effect after processing. Two forms of precipitates, namely δ-Ni2Si and γ-Ni5Si2, were identified and the sequence of their appearance was well established for ECAP processing and ageing. There was no detection of either a modulated structure resulting from spinodal decomposition or an ordered structure nucleated from the modulated structure. An X-ray hybrid pixel array detector (XPAD-S140 detector) permitted the detection of the nucleation stages of the δ-Ni2Si phase that began soon after 24s of ageing at 723K. There was also no trace of any amorphization of the matrix phase.