<p>The effect of iron and silicon impurities on the phase composition and hardening of Al‑0.3Zr-REM (REM = Er, Y, Yb or Gd) alloy ingots during annealing was studied. The Al₃Fe phase was observed in the Al‑0.3Zr alloy with impurities content less than 0.01%. Alloying of the Al‑0.3Zr alloy with REMs leads to the formation of (Al, Fe)₃REM phases. The Al₃Fe and Al₈Fe₂Si phases were formed in the Al‑0.3Zr‑0.5Fe‑0.5Si alloy. The Al₁₀Fe₂Er and Al₁₀Fe₂Y phases, as well as the Al₃Er₂Si₂ and Al₂Si₂Y phases, were crystallized instead of the Al₃Fe phase after Er or Y addition. The Al₂Si₂Yb or Al₂Si₂Gd phases with dissolved Fe were present in alloys with Yb or Gd. Iron and silicon impurities lead to a&#xa0;significant boost in hardness increase in all studied compositions during annealing at 400 and 440 °C. Hardening begins as early as 0.5 h into the annealing process and reaches its maximum after 8–11 h. The greatest hardening was achieved after annealing at 400 °C in alloys with erbium and ytterbium. High hardness after annealing of alloy ingots with impurities due to hardening by dispersoids and low silicon content in (Al) makes them promising candidates for creating current conductors characterized by high strength, thermal stability and electrical conductivity.</p>