Thermodynamic consideration of melting of copper based alloys with lanthanum in graphite crucible was carried out at 1,623 ∼ 1,873 K. Solubilities of lanthanum and carbon in liquid copper in the presence of C-LaC2 were determined: Lanthanum solubility in liquid copper under C-LaC2 equilibrium log(CLa/mass %) = 0.476 + 2.17 × 10-4 T (1,623 ∼ 1,873 K) Carbon solubility in liquid copper under C-LaC2 equilibrium log(CC/mass ppm) = 5.14 - 5.80 × 103/T (1,623 ∼ 1,823 K) Based on the result of lanthanum solubility, activity coefficient of lanthanum in liquid copper was calculated: logγLa = -0.306 - 2.25 × 10-4 T - 3.10 × 103/T (1,623 ∼ 1,873 K)
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