Thermal Stability of Al-Ni-Sc Alloy Fabricated by Equal Channel Angular Pressing

Improving the strength of Al alloys at elevated temperatures has been always the quest for metallurgists. Al-Ni alloys provide a high potential for applications at elevated temperatures. Moreover, equal channel angular pressing (ECAP) is one of severe plastic deformation (SPD) techniques that can produce ultrafine-grained alloys with a high specific strength. This work presents the microstructure and thermal stability of Al-3Ni-0.4Sc alloy (wt.%) fabricated by ECAP. The ECAP process was repetitively carried out for 5 passes (true strain ⁓5). The microstructure of ECAPed and heat-treated Al-Ni-Sc alloys were investigated by using scanning electron microscopy (SEM) with electron backscatter diffraction (EBSD) technique. Vickers’s microhardness test was done to evaluate the mechanical property and thermal stability of the alloy. The ECAPed specimen shows an increase in fracture and refinement of Al3Ni microfibers, leading to more homogeneity of Al3Ni phase in Al matrix. Al matrix grain size was also refined to 0.49 microns. Al3Sc was formed during the heat treatment and thus increased the thermal stability of the microstructure. The hardness of the specimen with Sc remained at 925±26 MPa when heated at 300 ºC for 120 mins. The ultrafine grains and the Al3Sc precipitates can help maintain the strength of the ECAPed specimen in long-term applications at elevated temperatures.