Investigation of phase equilibria related to fusion reactor materials: II. The ternary system Hf-Al-N

Abstract Phase equilibria in the ternary system Zr-Al-N are investigated. AlN coexists at 1273 K with ZrAl 3 , ZrAl 2 , Zr 2 Al 3 , Zr 3 AlN and ZrN; at 1573 K with ZrAl 3 , ZrAl 2 an ZrN. Thus AlN is thermodynamically unstable against zirconium or binary aluminum-zirconium alloys rich in zirconium. Zr 5 Al 3 with Mn 5 Si 3 -type structure is a binary low temperature phase but stabilized by nitrogen solution to higher temperatures, α-zirconium has an extended solubility for aluminum up to the melting region when stabilized by about 2 at% nitrogen. No other ternary solubilities are observed. The getter characteristics of the Zr-Al-alloy ST 101® for impurity control and hydrogen recycling in fusion reactors are discussed in terms of the phase equilibria within the ternary system.