Mechanically alloyed and SPS consolidated Ti-20Ta-7Mn-5Mg alloys
[ 1 ] Instytut Inżynierii Materiałowej, Wydział Inżynierii Materiałowej i Fizyki Technicznej, Politechnika Poznańska | [ D ] phd student | [ P ] employee
2021
abstract
english
EN The industry still finds new applications for titanium alloys, such as in aerospace, construction or medical. Titanium comes with excellent corrosion resistance, a good strength-to-weight ratio, and has relatively low density. Introducing additives to pure elements affects almost every aspect of the main component, i.e., mechanical, physical and thermal properties. Thanks to powder metallurgy, it is possible to obtain bulk material from the powder form without a porosity in the structure. Still, it requires setting correct sintering temperatures (favourably the lowest possible to maintain starting grain size), proper compression pressure (the highest possible, but lower than compression strength under elevated temperature for die and punch material) and time for each sintering step (the shortest for warming up and heating stage). In this study, mechanically alloyed titanium alloy (Ti-20Ta-7Mn-5Mg) powder has been sintered in the form of discs using an SPS machine. Every disc has been made out of 7 grams of powder. Subsequently, we investigated the influence of the sintering temperature (750°C, 850°C, 950°C) on the porosity, hardness and piston displacement charts under the same sintering conditions for all samples. With increasing temperature, porosity was decreasing 20,88±1,04%, 3,46±0,57% and 1,93±0,17%, respectively. Microhardness was increasing accordingly 482±159HV0,1 551±32,3HV0,1 and 548±8,22HV0,1. Due to the presence of porosity, there is an enormous variation in results for 750°C sample. Comparing the temperature chart with the piston displacement chart, it is possible to determine whether the consolidation process has been finished too soon with the given parameters or the heating stage should be further elongated. It must be pointed out that keeping samples at an elevated temperature long enough affects the grain size and influences the metastable structures if any have been achieved after mechanical alloying.
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