Onset of local ordering in some copper-based alloys: critical solute concentration vis-a-vis various solutionhardening parameters |
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Authors: | Muhammad Zakria Butt Mozina Noshi Farooq Bashir |
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Institution: | (1) Department of Physics, University of Engineering and Technology, Lahore-, 54890, Pakistan;(2) Central Research Laboratory, Lahore College for Women University, Lahore-, 54000, Pakistan |
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Abstract: | The mode of planar distribution of solute atoms in Cu single crystals alloyed with 0.5 to 8.0 at.%Ge has been investigated
via the temperature dependence of the critical resolved shear stress of these alloys. It is found that there exists a critical
solute concentration c
m
≈ 5 at.%Ge below which the distribution of solute atoms in the crystal is random, and above which some local ordering occurs.
This together with such data available in the literature for Cu-Zn, Cu-Al and Cu-Mn alloys, i.e. c
m
≈7 at. %Zn, 7 at.%Al and 1 at.%Mn, when examined as a function of the size-misfit factor δ = (1/b)(db/dc)of a given binary alloy system, shows that the value of c
m
strongly depends on δ; the smaller the magnitude of δ, the greater the value of c
m
and vice versa. Also, the value of c
m
is found to correlate well with the electron-to-atom ratio (e/a)of the Cu-Zn, Cu-Al, Cu-Ge and Cu-Mn alloys with the solute concentration c = c
m
. However, no systematic correlation exists between the critical solute concentration c
m
for the onset of local ordering and the modulus-mismatch parameter η = (1/G)(dG/dc).
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Keywords: | copper alloys yield stress temperature dependence composition fluctuations local order |
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