The effect of Sc additions on the microstructure and age hardening behaviour of...

• Author(s): Costa, Sónia ; Puga, Hélder ; Barbosa, J. ; Pinto, A. M. P.
• Date: 2012
• Persistent ID: http://hdl.handle.net/1822/26066
• Origin: RepositóriUM - Universidade do Minho
• Subject(s): Aluminium alloys; Grain refinement; Precipitation strengthening
• Document Type: Article
• Language: English

Description

The 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.