Abstract:

Objective　To investigate the influence of mold temperature on the mechanical properties of Ti-Zr alloy castings. Methods　Ti-Zr alloywas cast into a moldwhichwas made of a zircon ( ZrO2·SiO2) investmentwith a castingmachine (China) designed as vacuum, pressure and centrifuge. At three mold temperatures (room temperature, 300℃, 600℃) the Ti-Zr alloy was cast separately. The ultimate tensile strength (σb), 0.2% offset yield point strength (σ0.2), and elongation to fracture (δ) were determined by a universal testing machine with 15 mm pre-marked gauge interval. The surface micro-structures ofTi-Zr alloy castings at three mold temperatures were observed by optical microscope.Results　At a higher mold temperature during casting, the tensile strength and yield strength of Ti-Zr alloy were significantly increased, while the elongations were significantly de- creased. The micro-structure of the surface was different from the inner part. There was a reacted layer in the outermost surface. The thickness of reacted layers at the three mold temperatures was about 35.5μm (room temperature), 55.0μm (300℃) and 65.5μm (600℃), respectively. The inner part of microstructure composed of mainαphaseswithin the priorαgrain boundaries. Conclusion　The mold temperature is one of the major factors influencing Ti-Zr alloy mechanical properties. Comparing with Ti6Al4V alloy and Co-Cr alloy castings, Ti-Zr alloy is more suitable for denture frame.

Key words: Ti-Zr alloy, cast, mechanical properties