타이타늄 합금의 유동성 및 금속-주형반응성에 관한 연구

Abstract

Titanium alloys are widely used in the fields of aerospace, petrochemical, biomedical and sports industries because of low density, high specific strength and excellent corrosion resistance. Investment casting is the cost competitive process to fabricate complex shapes. However, investment casting of titanium alloys faces with a challenge to minimize casting defects such as porosity, surface reaction layer, so called α-case because of poor fluidity and high reactivity of titanium alloy melt. In this study, effect of alloy system on the fluidity and surface reaction by metal-mold reaction of titanium alloys were studied. Three different alloys, pure titanium(hereinafter noted as CP-Ti), Ti-6Al-4V(T64), Ti-6Al-4Fe-0.25Si(TAFS) were investigated in this study. The fluidity tests were conducted by using spiral type mold and then, we analyzed surface reaction layers by metal-mold reaction. ISM(Induction Skull Melting) was used for melting and casting of the alloys and investment casting was conducted with ZrSiO4 mold. The fluidity length of CP Ti was the longest and that of Ti-6Al-4Fe-0.25Si was the shortest. On the contrary, The thickness of surface reaction layer(α-case) of Ti-6Al-4Fe-0.25Si was thinnest and that of CP Ti was the thickest. In addition, we will discuss microstructure, hardness profile, SEM/EDS analysis, X-ray diffraction analysis of the casting specimens of titanium alloys