With a Lead Tin alloy explain what happens as a liquid cools

With a Lead Tin alloy, explain what happens as a liquid cools to a solid at room temperature for a composition to the left of a Eutectic point.

At least 200 words please! Thanks

Solution

In metal alloying, a binary phase diagram is very helpful to determine the phase it is in at a certain temperature and concentration. Lead-Tin systems are used in widely used, example of use is the lead tin solder for electronic components.The binary phase diagram could show the different phases that the mixture could occur. One important part of a binary phase diagram is the eutectic point. This is the point where the liquid mixture of two substance could solidify as a whole. No substance would solidify first. This point has a certain temperature called as the eutectic temperature. Eutectic point also correspond to a certain ratio of the two substance that would result to homogenous solidifying or melting.The eutectic temperature for lead – tin combination is 62°C. Three single-phase regions are , , and liquid L . The - phase is a solid-solution tin in lead. The - phase is a solid solution of lead in tin. The eutetic invariant point is located at 61.9 wt% Sn and at 183^o C. Maximum solubility compositions and melting temperatures are different from that of copper and silver. Compositions of and phases are very different, the eutectic reaction involves redistribution of lead and tin atoms by atomic diffusion. Simultaneous formation of and phases results in a layered (lamellar) microstructure, called eutectic structure. Formation of eutectic structure in lead-tin system. http://image.slidesharecdn.com/phy351ch5-131102034720-phpapp02/95/phy351-ch-5-20-638.jpg?cb=1383365260(image)