Al-Cr中间合金在熔融Al-Zn-Mg-Si-Fe镀液中的扩散反应研究

以Al-Cr中间合金锭和熔融Al-Zn-Mg-Si-Fe镀液为研究对象，研究了Al-Cr中间合金锭浸入含不同质量分数Fe的630 ℃熔融镀液15 h的扩散反应。使用扫描电子显微镜、能谱仪分析了扩散前后Al-Cr中间合金锭组织和成分的变化，同时研究了镀液中Fe质量分数对Cr溶解度的影响。研究发现，随着镀液中的Zn、Mg、Si、Fe长时间向Al-Cr锭内部扩散，Al-Cr锭中原有的Al基体的组织转变成了与镀液成分相近的组织，原有的富Cr第二相转变成了Al-Cr-Zn-Si相和Al-(Fe, Cr)-Si相。随着Al-Cr锭中的Cr向镀液扩散，镀液中Cr质量分数升高，并在5 h后达到饱和。由于Cr和Al、Fe、Si优先形成了Al-(Fe, Cr)-Si金属间化合物，因此镀液中的Fe显著降低了Cr元素的饱和溶解度，当镀液Fe质量分数由0.10%增加至0.42%时，镀液中Cr质量分数由0.047%～0.059%减少至0.012%～0.016%。

Study on the diffusion reaction of Al-Cr master alloy in molten Al-Zn-Mg-Si-Fe bath

The diffusion reaction of Al-Cr master alloy ingot in molten Al-Zn-Mg-Si-Fe bath was studied when Al-Cr ingot was immersed in the molten bath with different Fe mass fraction at 630 °C for 15 h. The microstructures and compostions of the as received and diffused Al-Cr master alloy ingots were analyzed by scanning electron microscope and energy dispersive spectrometer, and the effect of Fe mass fraction in the bath on the solubility of Cr was also studied. The results show that with sufficient diffusion between the solid ingot and the molten alloy bath, the composition and microstructure of the matrix of the as received Al-Cr ingot were turned to a composition and microstructure close to the bath due to the diffusion of Zn, Mg, Si and Fe in the alloy bath to the Al-Cr ingot. The Cr-rich secondary phases in the as received Al-Cr ingot were transformed into Al-Cr-Zn-Si phase and Al-(Fe, Cr)-Si phase. As Cr diffused into the alloy bath, the Cr mass fraction of the bath increased and reached saturation after 5 h. Since Cr and Al, Fe, Si elements preferentially formed Al-(Fe, Cr)-Si intermetallic compounds, the existence of Fe in the molten bath significantly reduced the saturated solubility of Cr. When the Fe mass fraction in the bath increased from 0.10% to 0.42%, the Cr mass fraction of the bath decreased from 0.047%-0.059% to 0.012%-0.016%.