| Summary: | 碩士 === 國立成功大學 === 材料科學及工程學系碩博士班 === 90 === Abstract
Because of light weight, high strength to weight ratio, excellent corrision resistance, biocompatibility and osteoinduction, titanium and some of its alloys have been important issues for medical implants. Among them, the β type alloys are now the main target.
The present work is a study of a series of heat and mechnical treatments on β type alloy: Ti-7.5Mo-2Fe.
Ti-7.5Mo-2Fe alloy can be cold rolled to the extent of 75% reduction in thickness without cracking. It shows that Ti-7.5Mo-2Fe alloy has good deformability.
Heat treated above β transus can get fully equi-axial β and better elongation; higher temparature or longer heat treatment time will cause fast β grain growth and lower the strength.
Heat treated below β transus will retain dislocations caused by cold working and increase the bending strength. Heat treated at 450°C will cause the precipitate of ω, which embrittles the material. The heat treatment condition of 750°C, 5min has the best comprehensive mechnical properties.
In aging condition, the bending strength will increse because of α precipitates. Aging at a temperature 100 degree lower thanβtransus can get the highest strength, but worse elongation. Aging at 650°C for 8 hours can get a comprehensive result.
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