The effect of Sc additions on the microstructure and age hardening behaviour of as cast Al–Sc alloys

Abstract

a b s t r a c tThe grain refinement effect and the ageing behaviour of Al-0.5 wt.% Sc, Al-0.7 wt.% Sc, and Al-1 wt.% Sc alloys are studied on the basis of optic microscopy (OM), scanning electron microscopy (SEM), X-ray diffraction (XRD) observations and hardness measurements. In Al-Sc alloys the higher grain refinement is observed for Sc contents greater than 0.5 wt.% accompanied by a notorious morphology modification, from coarse columnar grains to a fine perfect equiaxed structure. The as cast structures are characterized by a rich supersaturated solid solution in Sc, that promotes a great age hardening response at 250°C and 300°C. The age hardening curves also demonstrate a low overageing kinetics for all the alloys. Although the higher Sc content in solid solution for the alloys with 0.7 and 1 wt.% Sc, the age hardening response of all the Al-Sc alloys remains similar. The direct age hardening response of the as cast Al-0.5 wt.% Sc is shown to be greater than the solutionised and age hardened alloy.

Investigation of Microstructure And Mechanical Properties of Al-Zn-Mg and Al-Zn-Mg-Sc Alloys After Double Passes Friction Stir Processing

“…Sc is the costlier element and it can substitute by other rare earth elements and higher order alloy combination. The addition of Mg in binary Al-Sc alloys has been shown to form primary particles (Al3Sc) much lower that the eutectic composition of Sc in such aluminium alloys [24]. Mg improves the mechanical properties through solid solution strengthening.…”

Effect of scandium on structure and hardening of Al–Ca eutectic alloys

“…Fig.10 shows, that in the all studied states extra diffraction spots are identified in all the studied states. These spots of the precipitated phase L1 2 in the selected area diffraction pattern enable their identification by dark-field imaging using these superlattice spots [3,4], which are at the positions of prohibited reflections of the face-centered cubic aluminium matrix. In the state S300, which corresponds to the maximum hardening (Fig.11), the size of L1 2 precipitates inside (Al) dendrites is minimal (<5 nm).…”

Synergy of the Plastic Treatment HPT and Shot Peening in Aluminium Alloy Al-Mg-Mn-Sc-Zr

“…The 5xxx series of aluminum alloys is intended for heat treatment, however, a lack of alloy additions that allow for precipitation hardening means that these alloys do not achieve high mechanical parameters. A study carried out by Zaki A., Anwar U. and Costa S. and all, proves that doping 0.25% Sc into Al-Mg alloys causes an increase in durability to 375 MPa while maintaining an elongation of A = 29% [1,2]. The increase in durability, connected with intermetallic precipitates in Al3Sc, is achieved thanks to a high dispersion and density of phases.…”