A. Płachta

Physical and Mechanical Properties of Composites with Aluminum Alloy Matrix Designed for Metal Forming

The change of matrix and usage of the aluminum alloys designed for the metal forming in making the composite suspension allows to extend the processing possibility of this type of materials. The possibility of the metal forming of the composites obtained by mechanical mixing will extend the range of composite materials usage. Applying of the metal forming e.g. matrix forging, embossing, pressing or rolling, will allow to remove the incoherence of the structure created while casting and removing casting failures. In order to avoid the appearance of the casting failures the homogenization conditions need to be changed. Inserting the particles into the matrix influences on the shortening of the composite solidification. The type of the applied particles influenced the sedimentation process and reinforcement agglomeration in the structure of the composite. Opposite to the composites reinforced with one-phase particles applying the fasess mixture (glassy carbon and silicon carbide) triggered significant limitation in the segregation process while casting solidification. Inserting the particles into the AW-AlCu2SiMn matrix lowers the mechanical properties tension and impact value strength. The most beneficial mechanical properties were gained in case of heterofasess composites reinforced with the particle mixture of SiC and glass carbon. The chemical composition of the matrix material (AW-AlCu2SiMn) allows to increase additionally mechanical characteristics by the precipitation hardening reached through heat casting forming.

Strength–Energy and Structural Effects of Dynamic Deformation of Aluminum Alloy

This paper presents the results of dynamic deformation tests performed on aluminum alloy PA4. The studiem was carried out by using rotary hammer, in the range of high rate of deformation: 400 – 2000 s-1. The test were carried using a rotary hammer of RSO type owned by Silesian Technical University in Institute of Technology Metals. Before the dynamic deformation, the heating treatment was carried out allowed for eliminating structural effects resulting from the previous technological treatments and for obtaining the homogenous grain structure. The tests were carried out with linear velocity in the range of 5 – 30 m/s. After deformation the following mechanical characteristics were determined: deformation limit εg, strain rate , tensile strength UTS, impact strength U. Independently of the dynamic deformation tests were carried out tensile test under static conditions. Moreover bending test were performed on Charpy type hammer with initial impact energy equal 300 J. The analysis of the microstructure was carried out using scanning electron microscopy Hitachi S–3400 N.

The Effect of High Strain Rate on Properties and Microstructure of the Fully Austenitic High Mn Steel

In the paper, results of impact bending tests of a high-manganese steel of X30MnAlSi26-4-3 grade are presented. The tests were carried out using a flywheel machine, suitable for dynamic tensile tests and impact bending tests in the range of linear velocity of the forcing element from 5 ÷ 40 m/s. The obtained test results were compared with the results of impact resistance of the studied steel determined using Charpy machine. Structural investigations were carried out using light microscope and scanning transmission electron microscopy. Creating a mechanical twins at different strain rates was analyzed. The surfaces of fractures formed in the break point during bending tests were analyzed, and they indicate a presence of mixed transcrystalline fractures with a predominance of plastic fractures. Substructure studies revealed the presence of mechanical twinning induced in a high strain rate for the X30MnAlSi26-4-3 steel.

The Effect of Metal Forming Direction on the Tribological Properties of MMCp Composites

This article presents the results of the research on tribological composites with AlCu2SiMn matrix that underwent the process of extrusion. The research was conducted on the composites that underwent extrusion, which was carried out with a pneumatic press with a heated matrix of 14mm and 20mm diameter. The research was carried out under technical dry friction conditions in reciprocating motion. The results allowed to describe the influence of the plastic work direction on the tribological properties of the composites reinforced with silicone carbide and glassy carbon. The process of wearing was conducted in two directions: the perpendicular and parallel to the axis of the extruded composite rod. In the examined composites the tribological wear in the direction perpendicular to the direction of the extrusion was greater than wear in the parallel direction. The difference between the values for the parallel and perpendicular directions to the rod decreases with the increase of the degree of plastic work.

Assessment of the Deformation of Composites with Aluminum Matrix Designed for the Metal Forming

Applying the metal forming for the production of machine parts from the composites in the aluminum alloy matrix will allow to widen the range of the practical appliances in this group of materials. In order to reach such results not only the reinforcement with ceramic particles into the matrix should be inserted but also the basic metal forming parameters of created composites must be set and verified. The article shows the results of plastometric research carried on the composites with PA31 alloy matrix. The research was conducted on the turning plastometer possessed by the Faculty of Mechanical Engineering of the Silesian Technology University. On the basis of the results the yielding curves were set in the system forming stress σ true deformation ε. Good coating in the PA31-SiC system causes limitation of the ability to deformation as a result of the separating boarder destruction and leads to destruction of the composite at the much lower deformation value and ductile stress. In case of the composites with glass carbon as well as in homofases system (PA31+15%WS) and heterofase (PA31+15%(SiC+WS)) the ductile stress value increase as follows 10 % and 20%.