Issue 35

W. Ozgowicz et alii, Frattura ed Integrità Strutturale, 35 (2016) 434-440; DOI: 10.3221/IGF-ESIS.35.49 440 A CKNOWLEDGEMENTS he authors gratefully acknowledge financial support from the research project: Innovative sanitary sewage system DEMONSTRATOR +, NCBR under the contract No. UOD-DEM-1-591/001. C ONCLUSION he performed investigations of the CuNi2Si alloy and the analysis of obtained results allowed the following conclusions to be drawn: 1. The CuNi2Si alloy after supersaturation from the optimum temperature of 940°C shows homogeneous α solution grains of approx. 30µm with annealing twins and hardness of approx. 55HV. 2. The increase in deformation temperature of the tested alloy from 20°C to 800°C results in monotonic reduction in strength properties and non-monotonic change in plastic properties when the so-called ductility minimum temperature (DMT) occurs. 3. The minimum plastic properties of the tested alloy at DMT of approx. 550°C are as follows: elongation (A) – approx. 3% and reduction of area (Z) – approx. 1%. 4. In structure of the CuNi2Si alloy deformed in the range of DMT, the  solution grains with precipitations and micro- cracks at the boundaries of grains and twins have been revealed. The revealed effects confirm that the main cracking mechanism in the tested alloy at elevated deformation temperature is intergranular precipitation and slide at the grain boundary. 5. The tested alloy deformed in the range of DMT is characterised by brittle intergranular fracture with traces of plastic surface deformation. R EFERENCES [1] Rdzawski, Z., Alloyed copper, (monograph in Polish), Publisher Silesian University of Technology, (2009). [2] Ozgowicz, W., Physico-chemical, structural and mechanical factors of intergranular brittleness of α-bronzes at elevated temperature, Publisher Silesian University of Technology, Mechanika, 145 (2004), in Polish. [3] Nowosielski, R., Explication of minimum plasticity effect of mono-phase brasses, Mechanika, 135 (2000), in Polish. [4] Konieczny, J., Forming of the structure and application properties of precipitation reinforced titanium copper, Open Access Library, 4 (22) (2013) 1-114, in Polish. [5] PN-EN 12163 : 2011, Copper and copper alloys. Bars [6] Łoskiewicz, W., Orman, M., Systems of equilibrium of binary metal alloys, PWN, Warszawa, (1956), in Polish. [7] Masalski B., Binary alloy phase diagrams, ASM, Sec. Ed.(1990). T T