Effect of Sc on microstructure and mechanical properties of ZL205A alloy

Abstract

The microstructure and ageing precipitation behavior of ZL205A alloy with different addition of Sc were investigated by OM, SEM and TEM. The results show that the grain refinement effect of Sc (up to 0.12%, mass fraction, the same below) is not observed in ZL205A alloy; the residual particle W (AlCuSc) phase is formed after heat treatment when the Sc content is 0.06%, and transformed to strip-liked structure with the increase of Sc content in the grain interface; the dispersed phases Al3 (Zrx, Ti1-x) in ZL205A alloy are transformed to Al3 (Zrx, Tiy, Sc1-x-y), and the number of the dispersed phases increase with the increase of Sc content; when the Sc content is 0.06%, the ageing response, peak hardness increase slightly, and the yield strength increases by 4%; while the Sc content increases to 0.12%, the decrease of the solute concentration may reduce the number of the θ' phase due to the strip-liked W phase formed in the grain interface, which results in the dramatic decrease of the ageing response, peak hardness and mechanical properties; traces of Sc help to slow down the growth of θ' phase during the over-aged stage.

Keywords

• zl205a
• sc alloying
• ageing behavior
• dispersion strengthening
• precipitation strengthening