Some studies on Al-8.3Fe-0.8V-0.9Si alloy for near net shape casting

摘要

With the development of new generation high temperature aluminium alloys, simple techniques to produce them to near net shape by casting route have become necessary. It is well known that near net shape casting not only contributes to material saving but also to reduction of processing steps. Amongst the high temperature aluminium alloys, the Al-Fe-V-Si alloys system has attracted considerable interest due to its potential in automotive and aerospace applications. These alloys are generally prepared through the complex rapid solidification-powder metallurgical processing route. Thus, although the alloys possess good elevated temperature strength, ductility, fatigue and fracture toughness they have not found industrial application. An alternative method of conventional solidification for producing these alloys has been attempted in this work. A novel structural modification technique has been tried out with Mg/Ni-Mg master alloy to bring about alteration and refinement of the precipitate particles, which are otherwise ten-armed star-shaped and adversely affect the mechanical properties, to favourable cuboidal, hexagonal or other compact forms. It was observed that a number of arrest points occur in the cooling curve of the alloy, indicating that a variety of phases such as Al_(12)(Fe,V,Si)_6(Si,Mg)_5, Al_(15)(Ni,V,Fe)_6(Si,Mg), Al_3(Fe,V,Ni,Si,Mg) form during cooling. Quenching experiments were performed to identify the details of the phases formed. The features of the phases were studied using scanning electron microscope/EDAX and X-ray diffraction. Important properties required for near net shape casting such as the thermal expansion coefficient, fluidity, etc., have been studied and correlated with the phases.