Infiltration of Lead Base Alloys into Aluminum Base Sintered Materials

Abstract

In order to infiltrate lead base alloys into aluminum base sintered materials by the contact infiltration method, in which the infiltrants are contacted with skeletons, stable oxide films of alumina, which have little wettability to liquid metals on the internal surface of pores in the skeletons must be eliminated from the internal surface.
In this experiments, copper powder, which is useful to eliminate the alumina films from the internal surface of pores by the occurrence of liquid phase in the skeletons during the infiltrating process, was added 5% in weight to aluminum powder, as the raw material for making the skeletons. Moreover, tin was conbined from 0% to 50% by weight into the lead infiltrant in order to improve the wettability between the liquid infiltrants and the skeletons.
First, infiltrations into the skeleton were performed at 580°C for 30 min in pure hydrogen atmosphere having -40°C of dew point. Unfortunately, any infiltrants could not fully get into the skeletons.
Then, in the next, the infiltrations were performed again into the skeletons sintered under the eutectic temperature of 548°C in order to occur a large quantity of eutectic liquid of Al-33%Cu in the skeletons during the heating of infiltrating process, expecting the liquid infiltrants were drown into the pores by "prime effect" of the eutectic liquid. Consequently, satisfactory results were obtained, that is, infiltrating ratio was more than 90% when the infiltrant had a composition of Pb-50%Sn.