In situ formation of superhard Cu-B based composite by reducing reaction

► Pure B are always used for the preparation of Cu-B based composites, but it makes the preparation cost highly. ► In the present work, B2O3 is used to prepare Cu-B based composites, and the Cu-B based composites are prepared by reducing reaction of B2O3 with Cu-Al melt. ► The microhardness of the B-rich compound in Cu-10B alloy can reach 2973 HV, and the hardness of the Cu-10B composite has been improved significantly as compared to those of pure Cu. ► Moreover, CTE of Cu-10B alloy is much smaller than that of pure Cu, and the Cu-B composites have pretty good resistivity.