Issue 35

W. Ozgowicz et alii, Frattura ed Integrità Strutturale, 35 (2016) 434-440; DOI: 10.3221/IGF-ESIS.35.49 434 Focussed on Crack Paths Analysis of cracking of low-alloy copper stretched at elevated temperature Wojciech Ozgowicz Silesian University of Technology, Mechanical Engineering Faculty, 18a Konarskiego Str., 44-100 Gliwice, Poland Wojciech.Ozgowicz@polsl.pl Elżbieta Kalinowska-Ozgowicz, Klaudiusz Lenik, Aneta Duda Lublin University of Technology, Fundamentals of Technology Faculty, 38 Nadbystrzycka Str., 20-618 Lublin, Poland kalinowska-ozgowicz@tlen.pl, k.lenik@pollub.pl , a.duda@pollub.pl A BSTRACT . 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. K EYWORDS . Low-alloy copper; Plastic deformation; Structure; Mechanical properties; Brittleness; Process of cracking. I NTRODUCTION ow-alloy copper alloys are used in various ways. Most of them are applied in the electrical engineering and electronics. They are also 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]. L