Relationship between Tensile Properties and Casting Defect of Ti-29Nb-13Ta-4.6Zr for Biomedical Applications Cast by Dental Precision Casting Process Using Various Investment Materials

Abstract

Relationship between tensile properties and casting defect of newly developed β type titanium alloy, Ti-29Nb-13Ta-4.6Zr, for biomedical applications, and representative α+β type titanium, Ti-6Al-4V ELI, for biomedical applications cast by dental precision casting using commercial alumina, magnesia and modified magnesia based investment materials. Then the effect of specimen diameter on tensile properties of both cast alloys was also investigated.
Elongation of cast tensile specimens of both alloys slightly increases and strength of cast tensile specimen of Ti-6Al-4V ELI increases with reducing casting defects. Hardness of surface reaction layer decreases, and hardness of matrix decreases by about 50 Hv due to increasing cooling rate by reducing the specimen diameter from 3 to 2 mm in both alloys. The microstructures of both cast alloys refines with reducing specimen diameters, and the hardness of surface reaction layers and matrix of both alloys decreases. Therefore, increasing strength of cast Ti-6Al-4V ELI with reducing specimen diameter is attributed to reducing casting defects.