Effects of heat input on microstructure and mechanical properties of copper/steel bimetal by microzone melting

Copper/steel bimetal materials were obtained with cladding tin bronze on steel substrates by microzone melting. The changing of steels substrate temperature and microzone cooling velocity were simulated by ANSYS. Microstructure and mechanical properties of different region were investigated by optical microscopy(OM), X-ray diffraction(XRD), electron probe microanalysis(EPMA) and micro hardness tester. The results show that as the surfacing process went on, the temperature of the steels substrate increased obviously from 20 °C to 433 °C. The cooling speed decreased from 2 070 K/s to 336 K/s and the hardness of the surfacing layer decreased from 199 HV to 137 HV. The initial peripheral Tin-Bronze coating consisted of αCu, Pb and αFe, which were the product of the Cu-Fe liquid phase separation having a characteristic of metastable liquid phase separation. The grain size of αCu increased from 11.2 μm to 53.4 μm.