Manufacturing of Refractory Multi Principal Element Alloys and Understanding their Micro and Nanomechanical Behaviour

Abstract

It is desired to improve the thermal efficiency of gas turbine engines to decrease the global newlineproblem of CO2 emissions, thus reducing global warming. To improve the thermal efficiency newlineof the gas turbine engine, it is essential to increase the operating temperature of the gas turbine newlineengines. This induces high thermal stresses on the turbine engine components. To overcome newlinethis problem, an alternative material is required to sustain the high thermal loads during the newlineservice. Refractory multi-principal element alloys (RMPEAs) represent a dynamic class of newlinealloys with considerable potential for high-temperature gas turbine engine applications. newlineNotably, the MoNbTaW alloy has expanded the realm of high-temperature applications, newlinesurpassing Ni-based superalloys. Despite its impressive compressive strength at 1000 °C (548 newlineMPa), its high density of 13.62 g/cc hinders its applicability for aerospace applications, which newlinedemand materials with high strength and low weight. newlineIn a bid to enhance strength and reduce overall density, the current work introduced Ti to the newlineMoNbTaW alloy. The MoNbTaTiW alloy is manufactured via ball milling and spark plasma newlinesintering. It appears that Ti and Fe (from processing media) are responsible for the multi-phase newlinestructure realized as well as the extraordinarily high absolute hardness of 13.89 GPa at 500 g newlineload. These values are the highest reported so far in the family of MoNbTaW alloys. A newlinecomprehensive analysis on strengthening mechanisms responsible for the extraordinarily high newlinehardness observed in this alloy indicates that solid solution strengthening and grain boundary newline(Hall-Petch) strengthening are the dominant factors while lattice frictional stress and Taylor newlinehardening also contribute to some extent. The hardness data of this alloy was observed to newlinefollow the Meyer hardening power law with an index of 1.82 suggesting the presence of newlineindentation size effect. The strain gradient plasticity of this multi-phase RHEA was explained newlinebased on the considerations of GNDs that exists owing to the mul