A study was made of the weldability of 4-mm-thick aluminium-alloy 5083 plates using friction-stir welding. A plan of experiments was prepared based on the abilities of a universal milling machine, where the tool-rotation speed varied from 200 r/min to 1250 r/min, the welding speed from 71 mm/min to 450 mm/min and the tool tilt angle was held constant at 2. The factors feed per revolution (FPR) and revolution per feed (RPF) were introduced to get a better insight into the friction-stirring process. Samples for microstructure analyses, Vickers micro-hardness measurements and special miniature tensile-testing samples were prepared. The microstructure was prepared for observation on a light microscope under a polarised light source. A set of optimal welding parameters was determined at a FPR of 0.35 mm/r, at which quality welds can be made with a minimal increase in the weld hardness and an up to 15 % drop in the tensile strength.
COBISS.SI-ID: 12490011
A comprehensive research of Friction Stir Welding of 4 mm thick aluminium alloy (AlMg4.5Mn) for forming was done. A vast variety of process parameters was tested according to the plan of experiments at constant 2° tilt angle. Specialy designed tensile test specimens were sectioned perpendicular to the welding direction. The microstructure was prepared for the observation on a light microscope under the polarized light source. Vickers micro-hardness was measured. The results show the influence of FSW process parameters on the formation of the microstructure and mechanical properties.
COBISS.SI-ID: 12401435
The investigation of aluminium alloy die casting die failures was done with the emphasis on thermal cracks. The aim of the study was to prolog the in-service die life by cladding with maraging steels, which would be economically beneficial. A vast analysis of thermal fatigue cracks in aluminium alloy die casting is done. Immersion test apparatus was developed, which enables simulation of conditions during aluminium alloy die casting and enables controlled thermal fatigue testing of materials. Special specimens made of the AISI H13 tool steel were differently heat treated. On the edges of some specimens, the maraging steel is cladded using gas tungsten arc (GTA) welding. These samples are tested in as-welded and in optimally aged condition. After completion of a particular number of cycles, the specimen edge surfaces were examined visually. The specimens were then sectioned and examined with light and scanning electron microscopy (SEM). The energz-dispersive X-ray spectroscopy (EDS) mapping of areas around the cracks was done. The number and length of thermal fatigue cracks were statistically evaluated and a Vickers hardness profiles were measured. The results confirmeda good thermal fatigue resistance of the properly hardened H13 hot work tool steel. The surface cracks growth is accelerated by surface oxidati on.
COBISS.SI-ID: 12133403