On the basis of the photomicrograph (i.e., the relative amounts of the micro constituents) for the lead-tin alloy shown in Figure 9.17 and the Pb-Sn phase diagram (Figure 9.8), estimate the composition of the alloy, and then compare this estimate with the composition given in the legend of Figure 9.17. Make the following assumptions:
(1) The area fraction of each phase and micro constituent in the photomicrograph is equal to its volume fraction;
(2) The densities of the α and β phases and the eutectic structure are 11.2, 7.3, and 8.7 g/cm3, respectively; and
(3) This photomicrograph represents the equilibrium microstructure at 180°C (355°F).