Please explain simply and clearly step by step $($eg do not say 'read from diagram' or jump between stages $-$ explain clearly HOW it was read from the diagram, WHAT knowledge was applied$)-$ so I am able to answer similar questions. Explain in general the rules for understanding ternary diagrams.

Question $1-$ Answer all parts $($a$)$ to $($c$)$

$($a$)$ Figure $1$ shows an isothermal section from the $Sn-Pb-Bi$ ternary phase diagram. Three

alloy compositions, i$,$ ii and iii, are marked by blue dots. Assuming full equilibrium at this

temperature, write down the phases present, the phase compositions and the phase

fractions for each alloy composition $($i$,$ ii and iii$).$

Figure $1$: Isothermal section from the Sn$-$Pb$-$Bi ternary phase diagram. Plotted using

ThermoCalc $2021$b with the TCSLD$3$ database.

$($b$)$ Figure $2$ is an isothermal section of the $Sn-Pb-Bi$ phase diagram. Would you expect this

section to be at higher or lower temperature than Figure $1.$ Explain your answer.

$($c$)$ Consider the $Sn-Pb-Bi$ liquidus projection in Figure $3.$ For Scheil conditions, the

solidification reaction sequence for an alloy of composition $Sn-10\%Pb-60\%Bi($mass $\%)$ is:

$L,$ from $145-140C$

$L+,$ from $140-120C$

$L++$

at $120C$

Using a similar format, write down the reaction sequence for an alloy with composition

$Sn-60\%Pb-5\%Bi($again assuming Scheil conditions$).$ Next state how many phases will be

present at the end of Scheil solidification in this alloy?