Journal of Materials Processing Technology 150 (2004) 208–214 Dispersion-strengthening effect of Cu-based Mn, Al, and Zn rich alloys U˘ gur Sarı a , Sedat A ˘ gan b , ˙ Ilhan Aksoy b,∗ , Kutalmı˛ s Güven b , Nermin Kahveci b a Department of Computer Technology, Faculty of Education, Kirikkale University, Kirikkale, Turkey b Department of Physics, Faculty of Science and Arts, Kirikkale University, Kirikkale, Turkey Received 27 February 2002; received in revised form 3 July 2002; accepted 26 March 2003 Abstract In this systematic study, dispersion-strengthening effect of the Cu–25.91Mn (wt.%), Cu–26.62Mn–8.99Al (wt.%), Cu–22.17Mn–12.32Zn (wt.%) ingot alloys have been investigated. Samples were homogenized at a high fixed temperature in different periods and cooled with different cooling rates. After processes, microanalysis of the samples were interpreted by using scanning electron microscope (SEM) and weight percentages of the elements of the occurrence phases in the samples obtained by using electron dispersion spectroscopy (EDS) technique. Additionally, some characteristic properties of the heat treated samples with different conditions of Cu–Mn, Cu–Mn–Al, Cu–Mn–Zn ingot alloys were also discussed. © 2003 Elsevier B.V. All rights reserved. Keywords: Dispersion strengthening; Cooling rates; Microanalysis 1. Introduction There are some general considerations on determining how the characteristics of the alloys have been formed. Solid-state reactions of the alloys provide some useful in- formation to be used in the industry. In the solubility limits, it is possible to control the properties of an alloy by utiliz- ing dispersion-strengthening, solidification techniques, and cooling rates. The alloying elements may diffuse in the solid by dispersion-strengthening effect. It occurs more readily at a high temperature where diffusion is more rapid. Thus, the growth rates are controlled primarily by temperature. The relationship between growth and nucleation plays an important role in the phase transformation of solid-state reactions, just as in solidification of the alloys [1,2]. If solidification occurs rapidly, non-equilibrium solidification has been obtained. The cooling rates in the alloys at room temperature or in iced-water cause the appearance of small grained polycrystals. If the cooling rate is increased, the grain size of the crystal will decrease. When the cooling rate exceeds of a certain value, crystallization may not occur and the metals or alloys will solidify as an amor- ∗ Corresponding author. phous material [3]. The dispersion-strengthened alloys have multiple phases and often contain an inter-metallic com- pound which may be stoichiometric or non-stoichiometric. In Cu-based alloys, the major value of dispersion strength- ening is to produce the material that resists softening and grain growth at temperatures approaching the melting point of copper. Dispersion-strengthened Cu-based alloys are su- perior in structural stability to the precipitation hardenable alloys [4,5]. However, the dispersion strengthening reduces electrical conductivity in the alloy [1]. There have been a number of investigations on dispersion- strengthened Cu-based alloys. Work-hardening in dispersion- strengthened Cu-based alloys was studied by Okabe and Mori [6] and a dispersion-strengthening model was applied to the iron–copper system [7]. In Cu–Mn and Cu–Mn–Al alloys, it has been observed that microhardness (Vickers) of these alloys have decreased by increasing annealing temper- ature; on the other hand, increased by increasing annealing time at a fixed annealing temperature [8,9]. The annealing behavior and electrical resistivity measurements of Cu–Mn alloys have been investigated by Nicht et al. [10]. In this study, some properties of these Cu-based Cu–25.91Mn (wt.%), Cu–26.62Mn–8.99Al (wt.%), Cu– 22.17Mn–12.32Zn (wt.%) ingot alloys that are heat treated by dispersion-strengthening, solidification techniques, have been investigated. Heat treated samples were cooled down 0924-0136/$ – see front matter © 2003 Elsevier B.V. All rights reserved. doi:10.1016/S0924-0136(03)00619-8