Copper precipitation in FeCu, FeCuMn, and FeCuNi dilute alloys followed by X-ray absorption spectroscopy

Abstract

Samples of FeCu. FeCuMn, FeCuNi, and FeCuCr alloys containing 1.5 wt% of each solute have been electron irradiated around 2 9 0 T or thermally aged Y SOOT for various times. It is known that such treatments induce Cu precipitation; the Cu depletion of the mahix is measured by the resistivity decrease of the samples. The clystallographic environment of the solute atoms in the irradiated or aged samples has been studied by %AS (x-ray absorption spemoscopy).The data show that Cr, Mn, and Ni atoms mainly remain in BCC solid solution during the CO precipitation. The first Cu precipitates are found to be of BCC structure, i.e. coherent with the matrix. At the longest ageing times, they have become of Fa' smcture. In the electronirradiated samples, the data show that, up to a Ruence of5 C cm-', most of the Cu precipitates (> 80%) are still of Bn: structure.The fraction of BCC precipitates has been estimated from both Lhe x-ray-absorption near-edge structure (XANES) and extended x-ray-absorption fine-structure (EXAFS) data It appears that, for both FeCu and FeCuMn samples, similarly aged, the FCC fraction is larger in cold-rolled samples than in pre-annealed and quenched ones.The results obtained are consistent. in the FeCu case, with a simple linear correspondence between Ruence and time, 1 C cm-' at 3 0 0 T being equivalent to -IO h at S W T . The CO precipitation is found to be accelerated, at least in its first stages, by the presence of Mn in thc alloy.

Comparison of Precipitation Kinetics and Strengthening in an Fe-0.8%Cu Alloy and a 0.8% Cu-containing Low-carbon Steel

“…The addition of 1.3 % Mn was observed to decrease significantly the time to peak hardness, but to leave unchanged the net hardness increase due to precipitation. This was confirmed in terms of precipitation kinetics by Maury and co-workers, 10) who found that the precipitate size in a Fe-Cu-Mn alloy were larger than in a Fe-Cu alloy of same copper content (namely 1.3 %). The same authors did not find however any evidence of the presence of Mn inside the copper precipitates (as determined by X-ray absorption methods).…”

“…The same authors did not find however any evidence of the presence of Mn inside the copper precipitates (as determined by X-ray absorption methods). 10,18) This is in contradiction with the results of Maruyama,9) who found from FIM measurements evidence for Mn segregation at the iron/copper interface. However, this author found as well an acceleration of the precipitation kinetics with the addition of manganese.…”

“…7) The model Fe-Cu system has itself received much attention, and particularly in terms of the influence of irradiation on the precipitation process and the related embrittlement of the steels, for nuclear power plants applications. Extensive studies using lately high resolution transmission electron microscopy (HRTEM) 8,9) or X-ray absorption techniques such as EXAFS and XANES, 10,11) have determined the precipitation sequence applicable to these alloys:…”

Precipitation Kinetics and Strengthening of a Fe-0.8wt%Cu Alloy.

“…4,9) It is of interest to evaluate whether the same characteristics of the precipitation process can be applied to lower Cu alloying such as the present 0.8 wt%. The first ob- servation of significance from the present work is that the precipitate sizes measured with SAXS and TEM are consistent.…”

Numerical Simulation of Copper Precipitation during Aging in Deformed Fe-Cu Alloys

“…Here, an equation of effective interfacial energy for nucleation of a misfitting precipitate on an edge dislocation, derived by (11) where s is the ordinary nucleus/matrix interfacial energy, b is the Burgers vector of the dislocation, m is the shear modulus, n is the Poisson's ratio and e is the misfit strain of the particle in the matrix. In a Fe-Cu alloy bϭ2.47ϫ10 Ϫ10 m, nϭ0.3, mϭ81.6 GPa and eϭ0.01-0.03 [33][34][35] and thus, the 2nd term in the r.h.s. of Eq.…”