Low Temperature Rolling And Heat Treatment Of A New Type Beta Titanium Alloy For Biomedical Applications

Titanium alloys are the ideal biomedical metal materials and have been widely accepted in clinical application due to the excellent biocompatibility and mechanical properties.The traditional medical titanium alloys have toxic elements and high elastic modulus.Therefore,the development of a new type of medical titanium alloy with non-toxic and low elastic modulus is the focus of current research.In this paper,the influence of low temperature rolling and heat treatment process on microstructures and mechanical properties of new biomedical beta titanium alloy Ti-25Nb-10Ta-1Zr-0.2Fe(TNTZF,wt.%)were systematically studied by X-ray diffraction(XRD),optical microscope(OM),scanning electron microscope(SEM),transmission electron microscopy(TEM),mechanical test,etc.The main conclusions are as follows.At the process of low temperature rolling,the stress-induced martensite ? "transformed to lath-shaped martensite ?" in the alloys.The stress-induced ?transformed to V-shaped ? in low temperature rolling 80% alloy.Meanwhile,the dislocation density increased and the shear band began to appear.After low temperature rolling,the strength of the alloy increased.With the increase of deformation,the elastic modulus and elongation decreases.Under the condition of80% in the low temperature rolling,the alloy showed good comprehensive mechanical properties,a tensile strength of 1066 MPa,yield strength of 894 MPa,a the lower elastic modulus of 58 GPa,a moderate elongation(5.8%)and the highest strength to modulus ratio 18.4×10-3.For the low temperature rolling alloy with 40% reduction,the nucleation rate and grain growth rate will be faster with the increase of annealing temperature.After the40% low temperature rolling deformation alloy annealed at 750? and 800? for30 min,there have obvious recrystallized grains.When annealed at 850? for 10 min,many recrystallized grains have appeared in the alloy.With increasing the holding time to 30 min,the recrystallized grain size is increased to about 100?m.In the same annealing condition,the recrystallization grain nucleation rate of the alloy increase with the deformation increased.When the low temperature rolling alloy was annealed at 800 ?,the tensile strength and yield strength were significantly reduced,and elongation greatly improved.With the alloy was annealed,the tensile strength was in the range 720 to 856 MPa,yield strength was from 600 to 678 MPa,the range ofelongation is 12.8% to 26.7%.After solution treatment with air cooling and water cooling,the microstructure of the alloys are basically identical.The alloy will precipitate massive granular and short strip of ? phase at 670?.The ? phase begin to dissolve in the matrix and the ? grain nucleation occurs in some areas at 760?.There is only a single ? phase with large grain size in the alloy at 850 ?.At the same solution treatment temperature,the strength and microhardness of the alloy decreases with the increase of cooling rate.After solution treatment with air cooling and water cooling,the alloy show good plasticity,the elongation increase with the increase of solution treatment temperature.Under solution treatment at 850? by furnace cooling,the strength of the alloy is higher(?b=1002MPa),the elongation is lower(?=1.6%),the tensile fractuture morphology appears less dimple and obvious river pattern,exhibit the characteristic of poor plasticity.