Description
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Copper matrix alloys are of great importance in many technological applications. Due to the high electrical conductivity of copper they are frequently used in electrical engineering. These applications often require a high strength as well (e.g. in case of connectors). Whereas strength can be enhanced by foreign atoms and precipitates, electrical conductivity decreases with an increasing number of foreign atoms dissolved in the matrix. The optimisation of both strength and electrical conductivity is a challenge in the development of new copper matrix alloys.
The kinetic Monte Carlo method allows simulating precipitation. It leads to realistic structures with complex precipitates and foreign atoms dissolved in the matrix. Strengths of these structures are determined using molecular dynamics simulations. In simulated tensile and shear tests, interactions of dislocations with precipitates and foreign atoms are investigated. Electrical conductivities and electronic properties of interface structures are determined using ab initio calculations,./p>
State of the art
Experimental investigations revealed several copper matrix materials with both high strength and high electrical conductivity. They differ in chemical composition, shape, size and coherency of the embedded precipitates. A very high strength is obtained for alloys containing planar Ni2Si [1] or Be [2] precipitates. For obtaining very high electrical conductivities, Ag is a suitable alloying element which forms spherical or octahedral precipitates in copper [3]. Material properties can be further improved using additional alloying elements (e.g. Al, Mg or Cr) [4].
Whereas there are hardly any atomistic simulations of these materials, many studies have been performed regarding iron matrix materials. It was shown that the kinetic Monte Carlo method is suitable for simulations of precipitation [5,6]. Molecular dynamics is an established method that can be used to determine strengths by simulating tensile and shear tests which was also shown in iron with copper precipitates [7].
Literature
[1] Zhao, D.; Dong, Q.M.; Liu, P.; Kang, B.X.; Huang, J.L.; Jin, Z.H.: Aging behaviour of Cu-Ni-Si alloy. Material Science and Engineering A361, pp. 93-99 (2003).
[2] Monzen, R.; Seo, T.; Sakai, T; Watanabe, C.: Precipitation processes in a Cu-0.9mass% Be single crystal. Materials Transactions 47, pp. 2925-2934 (2006).
[3] Miyazawa, T; Fujii, T.; Onaka, S.; Kato, M.: Shape and elastic state of nano-sized Ag precipitates in a Cu-Ag single crystal. Journal of materials science 46, pp. 4228-4235 (2011).
[4] Lei, Q.; Li, Z; Xiao, T.; Pang, Y.; Xiang, Z.Q.; Qiu, W.T.; Xiao, Z.: A new ultrahigh strength Cu-Ni-Si alloy. Intermetallics 42, pp. 77-84 (2013).
[5] Soisson, F.; Barbu, A.; Martin, G.: Monte Carlo simulations of copper precipitation in dilute iron-copper alloys during thermal aging and under electron irradiation. Acta materialia 44, pp. 3789-3800 (1996).
[6] Hocker, Stephen; Binkele, Peter; Schmauder, Siegfried: Precipitation in α-Fe based Fe-Cu-Ni-Mn-alloys: behaviour of Ni and Mn modelled by ab initio and kinetic Monte Carlo simulations.
Applied Physics A 115, pp. 679-687 (2014).
[7] Molnar, David ; Binkele, Peter; Hocker, Stephen; Schmauder, Siegfried: Atomistic multiscale simulations on the anisotropic tensile behaviour of copper-alloyed α-iron at different states of thermal ageing. Philosophical Magazine 92, pp. 586-607 (2012).