Abstract: According to the eutccticum content of the Fe-Mg system,the standard free energy change of the following reaction is calculated.The result is as follows
Mg_(g)=[Mg]_1%(Fe) △G°=-108,993 + 63.25 T,J/g-at
It is then impossible to produce or retain Mg content ≥ 0.002% by means of Si or Mn in the GH36 alloy while ESR is conducted with slag containing MgO or MgF₂.The necessity of containing a few Al in consumanle-electrode during ESR has been proposed.The effect of the original contents of Al,Mg and the the composition of slag system CaF₂-MgO-Al₂O₃-CaO on the content of Mg in ingot is investigated.At temperature of the slag pool is about 1690±10℃, 0·32 ≤ [Al]_o ≤ 0.62wt%,0.0035 ≤ [Mg]_o ≤ 0.014 0 wt% and in the mole concentration range of the slag. 0.10 ≤ N_Mgo ≤ 0.30,0.05 ≥ N_At2O3 ≤ 0.21, N_CaO ≤ 0.15, the Mg content in the GH36A alloy after ESR may be controled.
It is found that the smooth and notched stress rupture life of the GH36A alloy contained suitable Mg and Al contents may be substantialy improved,and the notch sensitivity of the alloy may be eliminated under esting temperature of 650℃ and stress of 372.65Mpa