Effect of Tin Addition on the Precipitation and Phase Transitions in Supersaturated AI-Cu alloys

Abstract

In the present work, the effect of addition of Cu and Sn on the mechanical, thermal and electrical properties of Al-Cu binary and Al-Cu-Sn ternary alloys have been studied. For this purpose, five Al-Cu alloys having different Cu concentrations as Al-x at.% Cu (x=0.5, 1.0, 1.5, 2.0 and 2.5) and three Al-2.0 at.% Cu-y at.% Sn alloys (y=0.05, 0.10 and 0.15) have been prepared. The microhardness measurements of the specimens have been performed using Vickers tester after the isochronal aging of the as-quenched specimens from the solid solution state (803 K). The electrical resistivity measurements during continuous heating have been followed in the temperature range (300 K - 773 K). Differential scanning calorimetry, DSC, electron microscopy (scanning electron microscopy, SEM, and transmission electron microscopy, TEM) and X-ray diffraction, XRD, techniques have been used to confirm the obtained results.

In the as-quenched specimens from 803 K into chilled water(- 273 K), the microhardness, HV, for the binary alloys Al­ Cu increases with increasing Cu concentration from - 200 MPa for pure AI to- 580 MPa for Al-2.5 at.% Cu. On the other hand, for Al-2.0 at.% Cu-y at.% Sn ternary alloys. the microhardness decreases with increasing Sn concentration from - 490 MPa for Al-2.0 at.% Cu to- 310 MPa for Al-2.0 at.% Cu-0.15 at.% Sn.