Small batches of two oxide powders falling in the particle size range of about 30-230 μm were received from industrial sources and were electroless nickel (EN) coated in order to prepare properly modified reinforcing particles for further laboratory experiments with the Laser Melt Injection (LMI) technique to produce particle reinforced steel composite surface layers. The partially calcined alumina (Al2O3) as well as the hydrothermally recycled crystalline iron(III) oxide precipitate were characterized first to check their exact size ranges, specific surface areas and major chemical contaminants so that the best possible EN plating technique would be selected and applied. It was revealed soon that the sensitization and activation pre-treatment steps could not be omitted and after their proper adjustment, also the composition and pH of a relatively commonly used hypophosphite reducing type bath had to be modified to the given purpose. Eventually a slightly alkaline EN bath was successfully prepared with which both industrial oxide powders surface could be nickel coated soundly, which final result was demonstrated also by several metallographic testing techniques showing the microstructure of the quite evenly and fully coated oxide particles.
Al/SiC composites are used especially in automotive and aerospace industry due to the numerous advantageous mechanical properties. These end-products can be produced by casting or powder metallurgical techniques. High strength with high toughness can be reached only by perfect interfacial bonds between the matrix and reinforcing phase. To improve the interfacial bond, one of the methods is the surface coating of the SiC particles. But the metal layer of the reinforcing phase reacts with the matrix due to the high sintering temperature and long sintering time. In our research work the formation of Al-Ni intermetallic phase was investigated by Scanning electron microscopy (SEM) and X-ray diffraction measurements (XRD).
Három különböző Fe/Mn arányú EN AW-8006 ötvözetet vizsgáltunk. A gyártástechnológiai műveletsorban a hidegalakítások között végzett közbenső lágyítás és a gyártás végső műveleteként végzett lágyítás hőmérsékletét változtattuk. Az így kapott mintákon szakítóvizsgálatot és keménységmérést végeztünk. A vizsgálati eredmények alapján a kémiai összetétel hatását elemezve arra a következtetésre jutottunk, hogy csak a folyáshatárra van a vastartalom növelésének kismértékű hatása a közbenső lágyítás nélküli minták esetén, valamint a vastartalom változtatása a végső műveletben lágyított termék szemcseszerkezetét finomította a referenciaanyagéhoz képest.
In the research work the precipitation hardening and/or equal channel angular pressing (ECAP) of PM aluminium alloy (AlCuSiMg) samples were investigated. The aim of the research was to determine the optimal parameters for precipitation hardening, especially temperature and time (in terms of maximal strength), and to test the ECAP pressing number for the same properties of precipitation hardened samples. The samples produced were studied by SEM, X-ray diffraction. The results showed that the PM samples had higher mechanical properties after one pressing by ECAP than after precipitation hardening with optimal parameters. In severe plastic deformation a heated die with a channel angle of 90° and ‘A’ route was used. During the heat treatment the applied temperature of the solution treatment was 420-540°C for 1 hour or 3 hours, and hardening was applied at 180°C for 5 hours.
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