Trends in the Development of Machinery and Associated Technology ” TMT 2010 , Mediterranean Cruise , 11-18 September 2010 ANNEAL HARDENING EFFECT IN SINTERED COPPER ALLOYS DEPENDENCE ON ALLOYING ELEMENTS AND DEFORMATION
This paper reports results of investigation carried out on sintered copper alloys: Cu-8at%Ni, Cu8at %Zn, Cu-8at%Al, Cu-8at%Ag, Cu-4at%Ni-4at%Sn, Cu-4at%Ni-4at%Zn and Cu-4at%Au. For comparison, investigation carried out on the sintered copper. The sintered alloys, as well as pure copper, were subjected to the same thermomechanical treatment. Thermomechanical treatment included cold rolling of 30,50 and 70% in reduction. Isochronal and isothermal annealing up to the recrystallization temperature were performed, followed with hardness and electrical conductivity measuring. This investigation shows that hardness and electrical conductivity of cold deformed copper-alloys increase after annealing in the temperature range of 160 400°C, due to anneal hardening effect. Electrical conductivity decreases with increasing the amount of alloying elements. During the annealing the electrical conductivity slowly increases for both set of the samples copper and alloys due to recovery and recrystallization
The mechanism of anneal hardening in dilute copper alloys
Copper alloys containing 4 at. pct of a solute (Al, Au, Ga, Ni, Pd, Rh, and Zn) were cold worked and annealed below the recrystallization temperature to study the effect of different solute species on the anneal hardening. By measuring the flow stress at small bending strains, it was found that anneal hardening occurs with all solutes and that the magnitude increases with the misfit of the solute atoms. This indicates that solute segregation to dislocations and the resulting binding force is the primary cause of anneal hardening.
Measuring Sheet Resistances of Dielectrics Using Co‐Planar Hydrogel Electrochemical Cells with Practical Applications to Characterize the Protective Quality of Paints on Sculptures
Electrical properties of thin dielectric films at the solid-liquid phase boundary are an important performance characteristic of many devices, coatings and sensors. In this paper, co-polymeric hydrogels of polyacrylic acid co-sulfonic acid, swollen with a salt solution to act as the solid electrolyte, were used to assess interfaces using electrochemical impedance spectroscopy (EIS) in a co-planar geometry. Silane-modified glasses were characterized by the co-planar hydrogel EIS cell and found to be distinguishable based on their surface monolayer chemistry. EIS measurements were also made on primed and painted metal substrates, using both test panels and an outdoor sculpture, Tony Smith's Stinger. The panels were then exposed to accelerated and outdoor weathering and showed degradation on the surface paint layers, which was observable electrochemically using EIS and confirmed visually by SEM. Electrochemical spectral features were compared between data from a standard paint-test cell versus this co-planar hydrogel cell; both cell types were able to measure coating capacitance, providing useful information about the condition of the bulk coating. Yet, sheet resistance (Rs) was a spectral feature seen only by the co-planar hydrogel cell. Thus, it can be concluded that the use of such co-planar hydrogel cells can provide an earlier warning sign to coating degradation and such cells provide a new type of spectral information that is not assessable by the standard geometry.