Grain refinement and microstructural effects on mechanical and tribological behaviours of Ti and B modified aluminium bronze

Microstructural effects on mechanical and tribological behaviors are studied for a series of aluminum bronzes with different microstructures. ASTM 1045 and 52100 steels were used as the counterparts in the friction and wear tests. Experimental data show that the coefficients of friction, wear rate, and mechanical properties strongly depend on the volume fraction of alpha-phase present in the alloy and, to a lesser extent, on the average alpha-grain size. The minimum coefficients of friction and the wear rate correspond to a yield strength of 370 N/mm and a bulk hardness of HB 168. Except for extreme low average alpha-grain size (corresponding to low volume fraction), both the coefficients of friction and the wear rate show linear relations with the reciprocal of the yield strength of the alloy, but not to the reciprocal of the hardness as expected. Based on these results, a design principle for high strength wear-resistant aluminum bronze has been developed. (Author)