The effects of mo, sb, b or b2o3 additions on the mechanical and microstructural properties of the pb-sn-cu alloys.

ABSTRACTMaster ThesisTHE EFFECTS OF Mo, Sb, B or B2O3 ADDITIONS ON THE MECHANICAL ANDMICROSTRUCTURAL PROPERTIES OF THE Pb-Sn-Cu ALLOYS.Murat KARTALFırat Universitylnstute of Natural SciencesDepartment of Metallurgical Education2006, Page: 66In this study the effects of 5-6 % B2O3, 5-6 % Sb and 3-4 % Mo on the mechanical andmicrostructural properties of a journal bearing alloy containing 73,4 % Pb, 23,4 % Sn, and 3,2 % Cuhave been investigated.Pb based bronse alloys can be used as high speed bearing material and they are therefore,very important for bearings techniques. It is very interesting to investigate their mechanical andmicrostructural properties.For this aim, the alloyS which had a chemical composition above are melted in a metallic ironcrucible. Molybdenum, antimony and boron oxide powders was added to melted alloys and thenmixed mechanically until the solidification of melted alloys were finished. To achieve to a homogenemix the melting and solidification processes were repeat fifth times one after the other.After casting of needed alloys, the effects of Mo, Sb and B2O3 particles on the microstructuraland mechanical properties of these alloys have been investigated with use of the metallographic andmechanical test methotds. The changes of mechanical and micro structural characteristics have beeninspected by scanning electron microscopy (SEM), electron dispersive spectroscopy (EDS), X-raydiffraction (XRD), differential thermal analysis (DTA), thermal gravimetry analysis (TGA), strengthand hardness tests.In the first chapter, an introduction to Pb-Sn-Cu alloys and the knowledge about these alloysare given. In second chapter, materials and method, technical characterctics of used elements andcompounds, lead alloys, cast techniques of non ferrous metals, etching solutions of lead alloys areexplaned. In third chapter, the production techniques of test materials and the experimantal studies arepresented. In fourth chapter, the results of experiments, conclusion and recommendation were given.As first result, the ductuality of 72-74% Pb, 23-24% Sn, 3-3,5% Cu alloy have been decreasedby boron oxide and antymony particles addition. But molybdenum?s addition has been retarded theIbreaking off of the test materials and increased the ductility of Pb-Sn-Cu bronse alloy. All additionsof B or B2O3, Sb, Mo have been increased the hardness of alloy and decreased the melting pointsslightly. The existing phases after casting are α β eutectics, Cu-Sn α-phase, Cu3Sn ε-phasePb+ Snstructures. B2O3 and Mo particles help to formation of crystal cores.Keywords: Pb-Sn-Cu alloys, Boron oxide, Antymony, Molybdenum, Microstructure, DTA,XRD, Mechanical Properties, Casting.II