Wpływ warunków wytwarzania na właściwości użytkowe materiałów proszkowych konsolidowanych w procesie wyciskania : praca doktorska /

Recenzenci pracy: Eugeniusz Łagiewka, Józef Zasadziński.Praca doktorska. Akademia Górniczo-Hutnicza im. Stanisława Staszica (Kraków), 2005.Bibliogr. k. 89-96.Formowanie proszków, spieków, na zimno, spiekanie, prasowanie na gorąco oraz spiekanie pod ciśnieniem, materiały proszkowe w procesach przeróbki plastycznej, metody zagęszczania materiałów proszkowych, proces wyciskania jako metoda wytwarzania wyrobów, półwyrobów z proszków metali, wpływ temperatury na odkształcania tworzyw metalicznych, warunki temperaturowo-prędkościowe procesu wyciskania, charakterystyka stopu AlSi26Ni6Fe2, AlCuMgAgZr, sposób wytworzenia materiałów do badań, badania metaloznawcze proszków, stanowisko badawcze, konsolidacja, wyciskanie na gorąco, metodyka, określenie gęstości, wyciskanych prętów metodą geometryczną, opartą na prawie Archimedesa, pomiary twardości, struktury, przygotowanie próbek do badań metalograficznych, badania makrostruktury stopów, mikrostruktury, charakterystyki mechaniczne odkształcenia wyznaczone w próbach ściskania i rozciągani

FEM Numerical and Experimental Study on Dimensional Accuracy of Tubes Extruded from 6082 and 7021 Aluminium Alloys

The extrusion of hollow profiles from hard-deformable AlZnMg alloys by using porthole dies encounters great technological difficulties in practice. High extrusion force accompanies the technological process, which is caused by high deformation resistance and high friction resistance in extrusion conditions. As a result of high thermo-mechanical loads affecting the die, a significant loss of dimensional accuracy of extruded profiles can be observed. The different projects of porthole dies for the extrusion of Ø50 × 2 mm tubes from the 7021 alloy were numerically calculated and then tested in industrial conditions by using a press of 25 MN capacity equipped with a container with a diameter of 7 inches (for 7021 alloy and 6082 alloy for comparison). New extrusion die 3 with modified bridge and mandrel geometry and a special radial–convex entry to the die opening was proposed. FEM was applied to analyse the metal flow during extrusion, geometrical stability of extruded tubes and the die deflection. The photogrammetric measuring method was used to evaluate dimensional accuracy of tubes extruded in different conditions and geometrical deviations in porthole dies elements, especially the bridges and the mandrels. Research revealed a high dimensional accuracy of tubes extruded from the 6082 alloy and from the 7021 alloy by using original extrusion die 3, while much higher dimensional deviations were noted for tubes extruded from the 7021 alloy by using extrusion dies 1 and 2, particularly in relation to the circularity, centricity and wall thickness

Microstructure and in vitro evaluation of extruded and hot drawn alloy MgCa0.7 for biodegradable surgical wires

The MgCa0.7 alloy may be a promising material for biodegradable surgical wires. In this paper, the technology for producing surgical wires from this alloy has been developed, based both on finite element modelling and experimental study. In particular, the extrusion and hot-drawing effects on the mechanical properties, microstructures, in-vitro rates of biocorrosion, and cytotoxicity to human cancer cells (SaOS-2) and healthy (hPDL) ones, have been determined. An approximately 30-40% increase in corrosion rate due to increasing hot-drawing temperature was observed. An effect of hot-drawing temperature on cytotoxicity was also found. Notably, at various stages of the final wires’ production, the MgCa0.7 alloy became toxic to cancer cells. This cytotoxicity depended on the alloys’ processing parameters and was maximal for the as-extruded rod and for the wires immediately after hot drawing at 440 $^{\circ}C$. Thus, the careful selection of processing parameters makes it possible to obtain a product that is not only a promising candidate for biodegradable surgical wires, but one which also has intrinsic bioactive properties that produce antitumor activity