3. Thermodynamics and Phases

Phase Diagrams — Quiz

Test your understanding of phase diagrams with 5 practice questions.

Practice Questions

Question 1

Consider a binary isomorphous phase diagram for a system of components A and B. An alloy with overall composition $C_0$ is slowly cooled from the liquid phase. At a temperature $T_1$ within the two-phase (liquid + solid) region, the liquid phase has a composition $C_L$ and the solid phase has a composition $C_S$. If the cooling rate is extremely slow, approaching equilibrium conditions, what is the primary mechanism by which the composition of the solid phase changes as the temperature continues to decrease through the two-phase region?

Question 2

A binary eutectic phase diagram for components A and B shows a eutectic point at composition $C_E$ and temperature $T_E$. An alloy with an overall composition slightly to the left of $C_E$ (hypoeutectic) is cooled from the liquid phase. Which of the following microstructural features is expected to form immediately below the eutectic temperature ($T_E$) under equilibrium cooling conditions?

Question 3

In a unary phase diagram, the slope of the phase boundary line between two phases (e.g., solid-liquid) is governed by the Clapeyron equation. For a substance where the solid phase is denser than the liquid phase (e.g., most metals), how does increasing pressure affect the melting temperature?

Question 4

An alloy of 60 wt% Ni and 40 wt% Cu is slowly cooled from the liquid state in an isomorphous Ni-Cu phase diagram. At a certain temperature, the alloy is in a two-phase region (liquid + solid). If the liquid phase has a composition of 50 wt% Ni and the solid phase has a composition of 70 wt% Ni, what is the weight fraction of the liquid phase?

Question 5

In a binary phase diagram, a peritectic reaction involves a liquid phase and one solid phase transforming into a different solid phase upon cooling. Which of the following accurately describes the general form of a peritectic reaction?