Search Results

You are looking at 1 - 5 of 5 items for

  • Author: J. Stobrawa x
Clear All Modify Search
Open access

Z. Rdzawski, J. Stobrawa, W. Głuchowski and J. Sobota

Abstract

The required functional characteristics expected from copper alloys have a major impact on the technological production process, therefore there is a strong need to acquire knowledge on changes of properties with technological process including heat treatment and plastic working. The studied in this work copper CuTi4. CuFe2. CuCr0.7 and CuNi2Si1 alloys was selected to present differences in hardening phases .The samples were quenched, cold deformed (rolling), and aged. Detailed microstructure analysis and its influence on electrical and mechanical properties was presented in the work. Quenched CuTi4, CuFe2, CuCr0.7 and CuNi2Si1alloys have different mechanism and kinetics of precipitation during aging. These processes are complex and depend on the heterogeneity of distribution of alloying elements in copper matrix, the process parameters and cold strain value.

Open access

Z. Rdzawski, W. Głuchowski, J. Stobrawa and J. Sobota

Abstract

Effect of addition of rare earth metals on microstructure and properties of copper alloys after casting, after cold working and after heat treatment was studies in this paper. Methodology consisted of microstructure investigations by optical microscopy and scanning electron microscopy. In addition, distribution of alloying elements and electron backscattered diffraction results (EBSD) were presented. The mechanical properties of a wire after tension test and after hardness measurements were described. Electrical conductivity test was performed using Foerster Sigmatest and Thomson bridge. Analysis of the microstructure and mechanical properties of investigated alloys after casting and after metal working showed possibility to produce materials with preferred set of functional properties.

Open access

J. Stobrawa, Z. Rdzawski, W. Głuchowski and W. Malec

Ultrafine Grained Strips of Precipitation Hardened Copper Alloys

Precipitation strengthened copper belongs to a group of functional and structural materials applied where combination of high electrical conductivity with high strength is required. A growing trend to use the new copper-based functional materials is observed recently world-wide. Within this group of materials particular attention is drawn to those with ultrafine grain size of a copper matrix.

This study was aimed to investigate mechanical properties and microstructure in strips of age-hardenable copper alloys processed by continuous repetitive corrugation and straightening (CRCS).

Tests were performed on 0.8 mm thick, CuCr0.6 and CuNi2Si1 alloys strips annealed at 650°C for 1 hour. The specially designed construction of die set (toothed rolls and plain rolls set) installed on tensile testing machine was applied for deformation process. The changes of mechanical properties (HV, ultimate tensile strength, 0,2 yield strength) as well as microstructure evolution versus number of deformation cycles were studied. The microstructure was observed with optical and electron microscopes (TEM and SEM equipped with EBSD).

The CRCS process effectively reduced the grain size of CuCr0.6 and CuNi2Si1 alloys strips, demonstrating the CRCS as a promising new method for producing ultra-fine grained metallic strips.

Open access

L. Wierzbicki, W. Malec, J. Stobrawa, B. Cwolek and B. Juszczyk

Studies Into New, Environmentally Friendly Ag-Cu-Zn-Sn Brazing Alloys of Low Silver Content

The paper present selected results of the research conducted for elimination of toxic cadmium from silver based brazing alloys of Ag-Cu-Zn-Cd type. The investigations were conducted with nine new alloys of constant, low silver content (25%) and diversified copper (38.8-46%), zinc (19-32%) and tin (3-10%) contents. Tin was selected as potentially the best cadmium substitute basing on literature review and analysis of equilibrium systems.

For examinations and tests a series of ingots in laboratory scale was manufactured, as well as some ingots in pilot scale for the selected, most promising alloys. Complex metallographic examinations of the brazing alloys samples produced in various conditions were made as well as analyses of their phase composition. Also mechanical properties of the samples both in ambient and in elevated temperatures were examined, and physical and technological properties and usability of the alloys were determined. The last stage of the study covered laboratory trials of brazing using the selected alloys.

Basing on the results it can be said that there is a possibility to substitute selected cadmium containing silver-based alloys with environmentally friendly alloys of Ag-Cu-Zn-Sn type of relatively low silver content. Low range of melting point was reached, as preliminary assumed. Mechanical properties of the studied alloys strongly depend on temperature, and present limited plasticity in room temperature, while at high temperature (over 500°C) present superplasticity. The examined alloys show good spreadability and the brazing tests confirmed their good reactions both with copper and brass base in a wide temperature range.

Open access

W.J. Głuchowski, Z.M. Rdzawski, J.P. Stobrawa and K.J. Marszowski

Abstract

Nowadays, there is much activity all over the world in development of Cu-Nb composites for their potential use as conductors in high field magnets. This study was aimed at investigation of microstructure, mechanical and electrical properties of Cu-Nb composite wires. The investigated materials have been processed by vacuum furnace melting and casting, and then hot forging and cold drawing. Initial results of research into Cu-Nb composite material obtained using repeated iterative drawing of niobium wires compacted into copper tube, have been also presented in this article. The ultimate tensile strength versus cold deformation degree has been presented. These changes have been discussed in relation to microstructure evolution. It was assumed that repeated drawing of compacted wires is a promising method for fibrous composite production (more than 823,000 Nb fibres of nanometric diameter) characterized by high mechanical properties and electrical conductivity. Original SPD technique applied for Cu-Nb composite deformation result in initial microstructure refinement and improves effectiveness of wire production process.