Date

2017

Author

Koç, Ömer Faruk

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Electrical conductivity together with some other mechanical properties like strength is needed for catenary systems in railway applications. In recent years, copper and its alloys especially the ones with Ni and Si which can mostly satisfy these mechanical needs are extensively researched. For this reason, uses of CuNiSi base alloys have become widespread. In the research study CuNiSi base alloys were put through several treatments to improve their properties. These treatments were basically melting and casting into permanent molds, solutionizing for appropriate temperatures, cold/hot working operations and heat treatments at different temperatures. Furthermore, microstructural analyses mainly grain size determination was carried out. In order to improve strength and shapeability of alloys, also grain size of 20-30μm was aimed. Throughout the study, scanning electron microscopy analysis, X-Ray diffraction analysis, hardness tests, bending tests, electrical conductivity tests were conducted. These tests and analyses were done to observe effects of different treatments on mechanical properties. A production route for optimum mechanical properties was designed. Additionally, hardness measurements were recorded as significantly higher for alloys with additional alloying element (CuNiSi-CrFe) on the other hand electrical conductivity was measured to be lower. SEM analyses revealed precipitate formation in the structure explaining this hardness increase. Namely, highest hardness measured is 120HB and average electrical conductivity measured is 42 %IACS for alloy composition of Cu%2,23Ni%0,34Si alloy. Grain size of this alloy after thermomechanical processing is in the range of 20-30 m. On the other hand, highest hardness measured is 180 HBN and average electrical conductivity measured is 34 %IACS for optimized alloy composition with Fe and Cr addition such as Cu%2,4Ni %0,6Si+%0,45Cr,%0,15Fe. Again, grain size of this alloy after thermomechanical processing is about 20-30 m. 

Subject Keywords

Metals, Metals, Metals, Copper alloys., Railroads.

URI

http://etd.lib.metu.edu.tr/upload/12621606/index.pdf
https://hdl.handle.net/11511/26807

Collections

Graduate School of Natural and Applied Sciences, Thesis