Comparative study on hot rolling of Cu-Cr and Cu-Cr-CNT nanocomposites

Cu-1%Cr (mass fraction) and Cu-1%Cr-5% carbon nanotube (CNT) (mass fraction) nanocomposite powders were produced by mechanical alloying and consolidated by hot pressing. Then, nanocomposites were hot-rolled by the order of 50% reduction at 650 degrees C. The structure and microstructure were investigated by X-ray diffractometry (XRD) and scanning electron microscopy (SEM). Relative density, microhardness, thermal stability, electrical and wear properties were evaluated. Compared to the Cu-Cr sample, the relative density of Cu-Cr-CNT sample is greatly improved from 75% to near full density of 98% by hot rolling. Although electrical conductivity and microhardness increase in both Cu-Cr and Cu-Cr-CNT nanocomposites after hot rolling, the effect of hot rolling on the enhancement is more prominent in the presence of CNTs. The microhardness and electrical conductivity of hot-rolled Cu-Cr-CNT nanocomposite approach HV 175 and 68% (IACS), respectively. Also, hot rolling is more effective on thermal stability improvement of Cu-Cr-CNT nanocomposite compared to Cu-Cr composite. However, after hot rolling, both the friction coefficient and wear loss of the Cu-Cr sample display higher reduction than those of Cu-Cr-CNT nanocomposite owing to different wear mechanisms. After hot rolling, friction coefficient and wear loss of Cu-Cr sample display variation of 25% and 62%, respectively.