PREPARATION AND SELECTED PROPERTIES OF CERTAIN DISPERSION-STRENGTHENED LEAD-BASE ALLOYS

Abstract

Dispersion-strengthened lead-copper and lead-aluminium alloys have been prepared by atomizing the alloys from a temperature at which the copper or aluminium was dissolved in the liquid lead. The particles of the resultant powders consisted of a very fine dispersion of a second phase in a lead matrix. The powders were compacted and extruded. The mechanical properties of the extrusions at room and elevated temperature have been determined and their microstructure examined.

At room temperature the alloys had a combination of tensile strength and ductility superior to most other lead alloys, including lead alloys strengthened by a dispersion of lead oxide. The strength of the leadcopper alloys increased with increasing copper content; this was attributed to the closer spacing of the,dispersed copper particles in the extrusions.

The creep of the alloys was investigated at room and at elevated temperatures up to 100°C. Lead-aluminium alloys containing 0·55% aluminium had steady-state creep rates of < 1%/year at stresses up to 2500 lb/in² at 25°C and up to 1200 lb/in² at 100°C. The creep-resistance of the lead-copper alloys was somewhat lower. Their steady-state creep rate at low stresses was proportional to the applied stress, while at high stresses it was proportional to the fourth power of the stress.