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通过热力学分析与试验研究了含金属氟化物的熔剂与A356铝合金中主要元素的反应,以及对铝合金组织与成分,熔剂组成相的影响,采用SEM、EDS和XRD进行组织和成分分析。结果表明,金属氯化物与A356主要元素的置换反应平衡常数大多低于氟化物,表明熔剂中的氯化物具有更好的化学稳定性。含NaF、SrF_2、BaF_2的熔剂中,氟化物较易与A356合金中的Al或Mg反应,在铝熔体中生成游离态Na、Sr、Ba原子,对共晶Si相有显著变质作用。含Na3AlF6的熔剂也会与铝液反应生成少量Na原子,对共晶Si相有一定的变质作用。含AlF_3、MgF_2和CaF_2的熔剂对A356铝合金组织没有明显影响。含NaF和BaF_2的熔剂可分别生成新的KMgF_3和BaFCl相,其他氟化物对熔剂成分没有明显影响。MgF_2、CaF_2、SrF_2和BaF_2由于熔点和密度高,容易在A356铝合金中残留。
The reaction between metal fluoride-containing fluxes and main elements in A356 aluminum alloy was studied by thermodynamic analysis and experiments. The effects of microstructure, composition and flux composition of aluminum alloy were studied. The microstructure and composition were analyzed by SEM, EDS and XRD. The results showed that the equilibrium constants of the displacement reaction between the metal chloride and the main A356 element were mostly lower than that of the fluoride compound, indicating that the chlorides in the flux had better chemical stability. Among the fluxes containing NaF, SrF_2 and BaF_2, the fluoride is more likely to react with Al or Mg in the A356 alloy to form free Na, Sr and Ba atoms in the aluminum melt and significantly deteriorate the eutectic Si phase. The flux containing Na3AlF6 also reacts with the aluminum liquid to generate a small amount of Na atoms, which has certain metamorphism on the eutectic Si phase. Fluxes containing AlF 3, MgF 2 and CaF 2 had no significant effect on A356 aluminum alloy. Fluxes containing NaF and BaF_2 produced new KMgF_3 and BaFCl phases, respectively. Other fluorides had no significant effect on the flux composition. MgF_2, CaF_2, SrF_2 and BaF_2 are easily remained in A356 aluminum alloy because of their high melting point and high density.