Influence of Ag micro-alloying on the thermal stability and ageing characteristics of a Cu-14Fe in-situ composite

This paper studied the influence of Ag micro-alloying on the thermal stability and ageing characteristics of a deformation-processed Cu-14Fe in-situ composite prepared by thermo-mechanical processing. Heat treatment caused (i) edge recession, longitudinal splitting, cylinderization, break-up and spheroidisation of the Fe fibres in the Ag micro-alloyed Cu-14Fe in-situ composite, and (ii) recovery, recrystallisation and precipitation in the Cu matrix. Ag micro-alloying caused these processes to occur at lower temperatures. The index Z (a combination figure of merit that assesses the service performance) reached the peak value of 3.3×107 MPa2·% IACS after isothermal heat treatment at 500 °C for 1 h, where IACS is the International Annealed Copper Standard, a measure of conductivity. The optimum combinations of tensile strength and conductivity were 1033 MPa and 56.6% IACS; 931 MPa and 58.9% IACS; or 851 MPa and 60.6% IACS. The tensile strength and conductivity of Ag micro-alloyed Cu-14Fe in-situ composite at η=7.8 after isochronal heat treatments were higher than those of the Cu-14Fe in-situ composite at each temperature.