Abstract: In a Pb-free copper-based sintered alloy containing from 1 to 30% of Bi and from 0.1 to 10% of hard matter particles having from 10 to 50 ?m of average particle diameter, the Bi phase has a smaller average particle diameter than that of the hard matter particles and is dispersed in the Cu matrix, or the hard matter particles having 50% or less of a contact length ratio with the Bi phase based on the total circumferential length of the hard particle, which are in contact with said Bi phase, are present in a ratio of 70% or more based on the entire number of the hard matter particles.

Abstract: [PROBLEMS] To provide a Cu—Bi—hard substance base sintered alloy in which the respective properties of Bi and hard substance can be satisfactorily exerted. [MEANS FOR SOLVING PROBLEMS] There is provided a Ph free copper base sintered alloy, comprising 1 to 30% of Bi and 0.1 to 10% of hard substance particles of 10 to 50 ?m average diameter, (1) wherein a Bi phase having an average particle diameter smaller than that of the hard substance particles is dispersed in a matrix of Cu, or wherein with respect to a Bi phase in contact with the hard substance particles, the ratio of presence of hard substance particles exhibiting a ratio of hard substance particle contact length to entire circumference of Bi phase of 50% or less is 70% or greater based on the total number of hard substance particles.