Solid-Solution Hardening

Abstract

The temperature and concentration dependences of the yield-stress are determined in the Cu/Zn system with polycrystalline brasses (0.03 to I .O at '10 Zn) and high-purity copper of the same grain size between 15 and 300 K. The data, as well as similar ones on other dilute copper alloys, given in the literature, are found to be well accounted for by the 'kink-pair-formation' model of solid-solution hardening, originally developed for concentrated solid solutions. At temperatures at which diffusional forms of recovery are absent, the model is shown to be applicable at all concentrations, with possiblc exceptions at levels below about 10-2%, and allows for the influence of work-hardening due to dislocations, present in the metal also in its solute-free 'ground state', on the process of solid-solution hardening. The kink-pair nucleation process is examined in dctail.Die Temperatur-und Konzentrationsabhangigkeiten der FlieMspannung wird im System Cu/Zn an Messing-Einkristallen 0,03 bis 1,0 At% Zn) und hochreinem Kupfer der gleichen KorngroDc im Bereich 15 bis 300 K bestimmt. Die Messungen, sowie gleichartige aus der Literatur entnommene Angaben iiber andere schwach legierte, auf Kupfer basierende feste Losungen, weisen auf die gute Anwcndbarkeit des Begriffes der Erzeugung von Kinkenpaaren, der friiher zur Erklarung der durch Legierung bedingten Verfestigung in konzentrierten festcn Losungen vorgeschlagen wurde, auch auf den Fall schwach legierter Metalle hin. Fur Temperaturen, bei denen keine diffusionsbedingte Erholung stattfindet zeigt sich das Modell bei allen Konzentrationen anwendbar; mogliche Ausnahmen diirftc man unter einem Niveau von ungefahr 10-20h erwarten. Die durch die Anwesenheit von Versetzungen bedingte mechanische Verfestigung, welche auch im legierungsfreien "Grundzustand" des Metalls vorhanden ist, wird im Modell beriicksichtigt. Einzelheiten des Kinkcnpaarbildungsprozesses werden erortert.

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

“…According to Feltham and Kauser [6], the unrelaxed dislocation pile-ups developing at grain boundaries in the course of an elastic relaxation, induce a progressive reduction in the mobility of new dislocations arriving from the grain interior. This leads to the concomitant decrease in the amount of stress relaxed (t) and in the magnitude of relaxation rate s; the smaller the grain size, the greater will be the retarding effect, and hence smaller the stress relaxed (t) and the relaxation rate s (Figs.…”

“…In early sixties, Feltham [2,3] point. Later, Feltham and Spears [4] extended this preliminary work to rather large strains deforming single crystals of copper and ␣-brasses (maximum shear strain ≈85%) at 77, 220 and 291 K. Similarly, Ghauri [5] investigated stress-relaxation in polycrystalline ␣-brasses containing 12, 20, 30 and 35 at.% Zn between 18 and 300 K. His measurements were, however, restricted to a narrow tensile strain range 3-5%, and the grain size for each brass composition was different ranging from 70 to 170 m. Furthermore, Feltham and Kauser [6] studied the dependence of stress-relaxation rate on the initial level of compressive stress, and on the temperature, in the near-linear work-hardening stage of high-purity copper and dilute brass (0.03-1.0 at.% Zn) polycrystals of grain size 130 m, at total strains of 2-5%.…”

“…Since then a lot of work has been done to explore stress-relaxation response of various metals and alloys (e.g. [2][3][4][5][6][7][8][9][10][11][12][13][14][15]) keeping in view their numerous technological applications. Like all other metals, copper and copper-based alloys are also susceptible to stress-relaxation.…”

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

“…The points in Fig. 4 denote the values of W o for Cu-Ni alloy single crystals containing 0.5-95 at.% Ni given in Table 1, while those for pure Cu and pure Ni crystals were taken from Feltham and Kauser [37] and Butt and Sattar [18], respectively. One can readily note that in the case of Cu-Ni alloys, Fig.…”

Effect of heat treatment and stress relaxation in 7075 aluminum alloy

“…In the past, stress relaxation has been studied extensively in high purity metals, e.g., copper [8], aluminum [9], nickel [10], tungsten [11], cobalt [12], iron [13], zirconium [14], and niobium [15] etc. from the viewpoint of basic research to develop and test models of relaxation mechanism in terms of dislocation movement in crystals.…”