TY - JOUR
T1 - An assessment of the homogeneity of nano-crystalline Fe–Cu powders as studied by means of APT
AU - Wille, Catharina
AU - Al-Kassab, Tala'at
AU - Choi, Pyuck-Pa
AU - Kwon, Young-Soon
AU - Kirchheim, Reiner
N1 - KAUST Repository Item: Exported on 2020-10-01
PY - 2009/4
Y1 - 2009/4
N2 - In this contribution the homogeneity of mechanically alloyed Fe-Cu powders for two different compositions (Fe-10 and Fe-2.5 at%Cu) has been systematically characterised by atom probe tomography. Since Fe-Cu exhibits the Invar effect, it is among the most attractive systems for technical application. Furthermore, this system is immiscible and characterised by a large positive heat of mixing. In combination with the widespread application and accessibility, this predestines Fe-Cu as a binary model alloy to elaborate the enforced nonequilibrium enhanced solubility for immiscible systems. Depending on the parameters composition and milling time, results on the extension of the solubility limit and on the homogeneity of the alloy are presented, discussed and compared to earlier works. Only for the alloy with lower Cu content and for the prolonged milling time of 50 h, chemical homogeneity of the sample as measured by the atom probe was fully reached on the nano-scale. For all other parameter combinations homogeneity could not be achieved, even for long milling times and for those samples that appear to be homogeneous via X-ray analysis. Moreover, impurities were determined, mostly stemming from the fabrication procedure. The arrangement and homogeneity of the most common impurity, oxygen, was evaluated from atom probe data for different samples. Thus, the local concentration, segregation effects and the distribution of impurities could be quantified on the nano-scale, depending on the different nominal compositions and processing parameters. Additionally, structural information could be gained employing transmission electron microscopy and diffraction measurements. (C) 2008 Elsevier B.V. All rights reserved.
AB - In this contribution the homogeneity of mechanically alloyed Fe-Cu powders for two different compositions (Fe-10 and Fe-2.5 at%Cu) has been systematically characterised by atom probe tomography. Since Fe-Cu exhibits the Invar effect, it is among the most attractive systems for technical application. Furthermore, this system is immiscible and characterised by a large positive heat of mixing. In combination with the widespread application and accessibility, this predestines Fe-Cu as a binary model alloy to elaborate the enforced nonequilibrium enhanced solubility for immiscible systems. Depending on the parameters composition and milling time, results on the extension of the solubility limit and on the homogeneity of the alloy are presented, discussed and compared to earlier works. Only for the alloy with lower Cu content and for the prolonged milling time of 50 h, chemical homogeneity of the sample as measured by the atom probe was fully reached on the nano-scale. For all other parameter combinations homogeneity could not be achieved, even for long milling times and for those samples that appear to be homogeneous via X-ray analysis. Moreover, impurities were determined, mostly stemming from the fabrication procedure. The arrangement and homogeneity of the most common impurity, oxygen, was evaluated from atom probe data for different samples. Thus, the local concentration, segregation effects and the distribution of impurities could be quantified on the nano-scale, depending on the different nominal compositions and processing parameters. Additionally, structural information could be gained employing transmission electron microscopy and diffraction measurements. (C) 2008 Elsevier B.V. All rights reserved.
UR - http://hdl.handle.net/10754/575664
UR - https://linkinghub.elsevier.com/retrieve/pii/S0304399108002647
UR - http://www.scopus.com/inward/record.url?scp=62549115289&partnerID=8YFLogxK
U2 - 10.1016/j.ultramic.2008.10.004
DO - 10.1016/j.ultramic.2008.10.004
M3 - Article
SN - 0304-3991
VL - 109
SP - 599
EP - 605
JO - Ultramicroscopy
JF - Ultramicroscopy
IS - 5
ER -