本文选用α-Al2O3作为矿化剂制备精密铸造用氧化硅基陶瓷型芯,采用X射线衍射仪、场发射扫描电子显微镜、能谱仪、三点弯曲试验等,研究矿化剂用量与硅溶胶强化处理对型芯的物相组成、显微组织、收缩率、显气孔率、密度和抗弯强度等的影响。结果表明：α-Al2O3对陶瓷型芯有双重作用,一方面其作为增强相能阻碍熔融石英的黏滞流动,提升型芯的强度;另一方面其优异的高温稳定性降低了陶瓷型芯的烧结致密度,进而导致型芯的收缩率和强度下降。而硅溶胶强化处理能有效封闭气孔,促进型芯烧结。经硅溶胶强化处理后,w(α-Al2O3)=2%的型芯的室温抗弯强度提升至16.6 MPa,高温抗弯强度为37.5 MPa,满足了精密铸造行业用陶瓷型芯的应用指标。
In this study, α-Al2O3 was selected as a mineralizer for the preparation of silica based ceramic cores used in precision casting. Techniques such as X-ray diffractometer, field emission scanning electron microscope, energy dispersive spectroscopy, and the three-point bending testing were employed to investigate the effects of mineralizer amount and silica sol strengthening treatment on the phase composition, microstructures, shrinkage rate, open porosity, density, and bending strength of the ceramic cores. The results indicate that α-Al2O3 exerts a dual effect on the ceramic cores. On one hand, it acts as a reinforcing phase that hinders the viscous flow of fused quartz and enhances the strength of the cores; on the other hand, its excellent high-temperature stability reduces the sintering density of the ceramic cores, leading to decreased shrinkage rates and strength. However, silica sol strengthening treatment effectively seals the pores and promotes sintering of the cores. After silica sol strengthening treatment, cores with w(α-Al2O3)=2% exhibit an increase in room temperature bending strength to 16.6 MPa and high-temperature bending strength to 37.5 MPa, meeting the application standards for ceramic cores in the precision casting industry.
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