The Systems Aluminum-Tin and Aluminum-Lead-Tin

Abstract

T h e solubility of tin in aluminum, between 400" and 645" C., has been determined by an isothermal method. The system Al-Pb-Sn has been investigated, isothermally, a t 500' and 600" C. The eutectic temperature and composition of this system have also been determined. T h e structure of the phases in completely solid alloys has been identified by photomicrography. The liquidus curves a t 500" and 600" C. are continuous, extending across the ternary diagram from the AI-Pb system to the Al-Sn system. On neither of the two isotherms does a twoliquid region occur, despite the fact that a well-defined two-liquid region exists a t temperatures above 650" C. This was found t o be due to inaccuracy in the published diagram for the AI-Sn system and this led to the work mentioned above. The solubility of tin in aluminum is much less than it has been supposed and this causes the surface of solid aluminum t o intrude into the solid diagram a t an early stage, thus blocking out the two-liquid region. The ternary eutectic temperature is 183.0" C. and the composition, 0.08 weight per cent Al, 38.1% Pb, and 61.7% Sn. I n any alloy a t room temperature, the solid phases are: primary aluminum, a-lead, and 8-tin. Brinell Ball and Viclcers Diamond Pyramid hardness tests show that the ternary eutectic alloy is the hardest of the system. When alloys approximating t o the eutectic composition are used as solders, it has been found that the alloy of ternary eutectic composition has a greater shear strength than ordinary solder.Despite the simplicity of the three-component system, Al-Pb-Sn, it has not been studied previously in its entirety; work has been confined to the completely liquid two-layer condition. Wright (101, working between 750 and 850" C., found the critical solution to contain 64 weight per cent tin and 17% lead. Lorenz and Erbe (4) carried out a few experiments a t 750" C., using a quenching technique, but their results are too crude to merit mention. Very excellent work was done by Davies (2) in 1953. He studied the region of partial miscibility a t 650°, 730°, and 800" C., using the purest materials and keeping the temperature truly constant. Davies' data are shown graphically in Fig. 1. I t is surprising that the numerical values were never published. We consider these data so valuable that we offer them here, with the consent of the author.Of the component binary systems, little need be said of the systems Al-Pb and Pb-Sn, save that they are simple and have been investigated completely. The system A1-Pb gives a t all temperatures above 658.5" C. two liquid layers; in the solid state there is no compound formation or appreciable solid solution (11).The Pb-Sn system, to which the soft solders belong, exhibits a simple eutectic accompanied by coilsiderable solid solubility of t i l l in lead, a t the eutectic temperature of 183.3" C., but this decreases to zero a t room temperature (6). The lead-rich alloys show a mysterious evolution of heat, on cooling, a t about 150" C., and for this no satisfactory explanat...

Melting Behavior of Al/Pb/Sn/Al Multilayered Thin Films

“…The presence of Al in the intermixed layers is reported to reduce the melting temperature of the eutectic marginally, and no additional phase equilibrium is reported in ternary Al-Pb-Sn system. [34] Thus, a minimum superheating of 3K is observed in the present case. The observed superheating can make the multilayers thin films potentially applicable for devices.…”