The heat capacity in two-phase regions and the heat of phase transformations of some alloys in $\text{Zr}$–$\text{Nb}$ and $\text{Zr}$–$\text{Sn}$ systems

Analytical expressions are given for the phase boundaries of diagrams of state for $\text{Zr}$–$\text{Nb}$ and $\text{Zr}$–$\text{Sn}$ systems. Thermodynamically justified temperature dependences of heat capacity of $\text{Zr}$–$1\%$ $\text{Nb}$, $\text{Zr}$–$2.5\%$ $\text{Nb}$, $\text{Zr}$–$1.5\%$ $\text{Sn}$, and $\text{Zr}$–$2.5\%$ $\text{Sn}$ alloys in two-phase regions are given and recommended for use. The heats of second-order phase transformations $\alpha(\text{Zr}) \Longleftrightarrow \beta(\text{Zr})$ in alloys of $\text{Zr}$–$\text{Nb}$ and $\text{Zr}$–$\text{Sn}$ binary systems are obtained, and the heats of monotectoid reaction $\alpha(\text{Zr}) + \beta(\text{Nb}) \Longleftrightarrow \beta(\text{Zr})$ in the $\text{Zr}$–$\text{Nb}$ system and of peritectoid reaction $\beta(\text{Zr}) + \text{Zr}_4\text{Sn} \Longleftrightarrow \alpha(\text{Zr})$ in the $\text{Zr}$–$\text{Sn}$ system are calculated.