Onset of local ordering in some copper-based alloys: critical solute concentration vis-a-vis various solutionhardening parameters

Abstract

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 ≈ 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.≈ 27 at. %Zn, 7 at.%Al and 1 at.%Mn, when examined as a function of the size-misfit factor δ = (1/ )(d /d ) of a given binary alloy system, shows that the value of strongly depends on δ; the smaller the magnitude of δ, the greater the value of and vice versa. Also, the value of is found to correlate well with the electron-to-atom ratio ( / ) of the Cu-Zn, Cu-Al, Cu-Ge and Cu-Mn alloys with the solute concentration = . However, no systematic correlation exists between the critical solute concentration for the onset of local ordering and the modulus -mismatch parameter η = (1/G)(dG/d ).

On the strength and stress-relaxation response of fine-grain Cu–42.2at.%Zn–0.6at.%Pb alloy polycrystals

“…Since the mechanical response of alloys is sensitive to the nature of solute distribution [19][20][21][22], dispersion of second-phase particles [23][24][25], etc., we shall now critically examine the published data on the strength of thermally-activable barrier, U o , which determines the stress-relaxation rate, s , in polycrystalline copper and ␣-brasses together with that obtained for Cu-42.2 at.%Zn-0.6 at.%Pb alloy in the present investigations. appertaining to 99.999 at.% pure copper and ␣-brass polycrystals containing nominally 12, 20, 30 and 35 at.% Zn, deformed by Ghauri [5] at room temperature, whereas the U o -value for 42.2 at.%Zn belongs to the present work.…”

Correlation between the temperature dependence of yield stress and the nature of solute distribution in Cu–Ni solid solutions

“…So is the case for other mechanical properties of solid-solution crystals, such as workhardening rate [22], internal friction [23], creep [22,24], stress relaxation [25,26], and strain rate sensitivity of flow stress [27]. To explore the relationship between the temperature dependence of critical resolved shear stress (CRSS) of solid-solution crystals and the nature of solute distribution, Butt and co-workers [13][14][15][16] carried out investigations with a number of copper-based binary alloy systems. They found that the CRSS of Cu-Zn [13], Cu-Al [14], Cu-Ge [15] and Cu-Mn [16] varies with the deformation temperature T in accord with the relation:…”

“…To explore the relationship between the temperature dependence of critical resolved shear stress (CRSS) of solid-solution crystals and the nature of solute distribution, Butt and co-workers [13][14][15][16] carried out investigations with a number of copper-based binary alloy systems. They found that the CRSS of Cu-Zn [13], Cu-Al [14], Cu-Ge [15] and Cu-Mn [16] varies with the deformation temperature T in accord with the relation:…”

“…As far as alloys are concerned, the non-random distribution of solute atoms has a marked effect on the principal features of solid-solution hardening, such as the temperature and concentration dependence of yield stress and associated activation volume [13][14][15][16][17][18], the stress dependence of activation volume [19], and the phenomenon of stress equivalence [9,20,21]. So is the case for other mechanical properties of solid-solution crystals, such as workhardening rate [22], internal friction [23], creep [22,24], stress relaxation [25,26], and strain rate sensitivity of flow stress [27].…”