Composition, microstructure, Vickers hardness and activation energies of Co–Cu alloys fabricated by arc melting technique

Abstract

We have determined the phase transition for the Co-20 and -30 at.% Cu alloys fabricated by arc melting technique, from the binodal to the two phases α + L as well as the peritectic transitions, using differential thermal analysis (DTA). We equally studied the effects of aging treatment, ranging from 3 to 35 h, on the alloy samples using scanning electron microscopy (SEM) and Vickers hardness (HV). The activation energies of these alloys are equally determined using five established models. Our results show that for aging time up to 15 h, within the spinodal region at 773 K, the hardness value for Co-20 and -30 at.% Cu alloys oscillates reaching a local maximum at the aging time of 8.5 ± 0.5 h. After 20 h of heat treatment, the HV for Co-20 at.% Cu alloy diminishes significantly while that of Co-30 at.% Cu effectively stabilizes at 241 MPa. The activation energies for the peritectic transformation based on Ozawa model are estimated to be 2465 and 2680 kJ mol⁻¹ for Co-20 and -30 at.% Cu, respectively.

†On leave for: Al-Jouf University, Skaka-2014, KSA.

Keywords:

• spinodal
• bionodal
• phase transformation
• differential thermal analysis
• Co–Cu alloy
• Vickers hardness

Notes

†On leave for: Al-Jouf University, Skaka-2014, KSA.