Papers by Author: Klaudiusz Gołombek

Abstract: The aim of this work is to determine the effect of a reinforcing phase and manufacturing conditions on the structure and properties of newly developed nanostructural powders of composite materials with the aluminium alloy matrix reinforced with natural halloysite nanotubes. Composite materials were manufactured employing as a matrix the air atomized powders of AA 6061 aluminium alloy and as a reinforcement the halloysite nanotubes. Composite powders of aluminium alloy matrix reinforced with 5, 10 and 15 wt.% of halloysite nanotubes were fabricated by high-energy mechanical alloying using a planetary mill. Elaborated composite powders were characterized for their apparent density, microhardness, particle size distribution and microstructure. A structure of newly developed nanostructured composite materials reinforced with halloysite nanotubes prove that a mechanical alloying process allow to improve the arrangement of reinforcing particles in the matrix material. A homogenous structure with uniformly arranged reinforcing particles can be achieved by employing reinforcement with halloysite nanotubes if short time of mechanical alloying is maintained thus eliminating an issue of their agglomeration.

Abstract: The thermomechanical processing of certain AHSS still represents a challenge due to the lack of complete data on their hot deformation behaviour. Therefore, the aim of this study was to provide data on the hot-working behaviour of four model steels of the type 0.17C-3Mn-1.5Al and 0.17C-5Mn-1.5Al with or without Nb microaddition. The paper presents the results of hot strip rolling simulated by multi-step compression tests using a Gleeble simulator. Analysis of microstructural features of steels with focusing on Mn and Nb contents was carried out using X-ray, LM (light microscopy) and SEM (scanning electron microscopy). It has been shown that the applied deformation schedule allows to develop very fine-grained transformation products of supercooled austenite and controlled cooling with isothermal holding at 400°C enables to retain from 13 to 18% of retained austenite with the blocky or lath-type morphology. Mn alloying in the amount of 3 to 5 wt.% does not affect hot deformation resistance contrary to Nb microaddition, which raises flow stress levels. Influences of Mn and Nb on the retained austenite content and its carbon content are discussed.

Abstract: The work presents the research results of modern composite materials. The matrix material was EN AC AlSi12 alloy while the reinforcement ceramic preforms, obtained through sintering process of Al2O3 Alcoa CL 2500 powder with addition of carbon fibers as pore forming agent burned out during sintering. The composites were produced with use of porous material pressure infiltration method. The main limitation of base technology is a difficulty in obtaining composite materials with volumetric participation of ceramic phase in amount not less than 20%. Obtained on the base of ceramic preforms composite materials were tested with scanning electron microscopy. Additionally, hardness and tensile test was performed for acquired materials. Achieved results indicate the possibility of producing, with use of pressure infiltration method, porous preforms composed of Al2O3 particles, new composite material with desired microstructure and properties, being a cheaper alternative for materials with base of ceramic fibers.

Abstract: Within the project framework the structure and properties was investigated of the cemented carbides, cermets and oxide ceramics using the scanning electron microscope (SEM). The X-ray qualitative microanalysis and surface distribution analysis of elements in the investigated materials were made using the EDS X-ray energy dispersive radiation spectrometer. The roughness measurements of the developed materials were made in two orthogonal directions. The Ra parameter was assumed to be the value describing surface roughness. The microhardness tests using the Vickers method were made on the dynamic ultra microhardness tester. The measurements were made in the „load - unload” mode.