Abstract
This paper presents both mechanical and structural aspects of micro-cracking of CuNi2Si copper alloy in CNCS grade revealed during the static tensile test in the temperature range between 20ºC and 800ºC. The purpose of this paper is to determine the impact of plastic deformation temperature and structural condition of the tested alloy on the type and mechanism of its cracking under specified deformation conditions. Therefore, the subject of the detailed metallographic analysis in a microscopic scale is the location of initiation and propagation of cracking, morphology of precipitations and their impact on the cracking process, nature and type of the fractures formed during material decohesion as well as microstructural analysis of the alloy by electron diffraction method. The obtained results allow the determination of the impact of analysed factors on cracking mechanism in the tested alloy as well as the specification of effective methods for limitation of the effects of cracking and thus the improvement in plasticity of alloy and workability of its products
Highlights
Low-alloy copper alloys are used in various ways
This phenomenon is a result of reduced plasticity at a specific deformation temperature, called the ductility minimum temperature (DMT)
The rise of temperature from 100°C up to 500°C has been found to result in insignificant reduction in Rm from 282 MPa to 239 MPa, while the rise of deformation temperature from 550°C to 800°C results in sudden decrease in strength from 189 MPa to 36 MPa (Fig.1)
Summary
Most of them are applied in the electrical engineering and electronics. They are used in the production of welding electrodes, elements of bearings, non-sparking tools and chemical apparatus. An important technological problem is the occurrence of brittleness in these alloys during hot plastic deformation. This phenomenon is a result of reduced plasticity at a specific deformation temperature, called the ductility minimum temperature (DMT). The copper alloy cracking mechanisms, which have not been fully explained yet, depend on many physicochemical, structural and mechanical factors related to the chemical composition (liquid films and segregations at the grain boundaries as well as inclusions and precipitations), structure of the alloy (grain size, crystallisation defects, non-uniform deformation) and deformation parameters (deformation temperature and strain rate, specimen surface condition, type of mechanical test) [1÷4]
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