| TM50 alloy possesses characteristics such as high strength, low elastic modulus and good property of cold deformation. Especially, TM50 alloy is used for dental cradlle, surgical implant materials, superelasticity spectacle frames and a great variety of elastic components, which is nontoxic and harmless to human body.The microstructure and properties, as well as the characteristic of deformation of TM50 alloy under different rate of cold deformation are studied in this paper. Also, the phase changing and mechanical properties of this alloy treated by aging after solution or cold deformation are analyzed. The main research efforts are as follows: Hot rolled bar of φ7.0mm is drawn by 20% to 80% through cold drawing. Tensile properties of alloy under different rate of cold deformation are tested and OM and TEM analysis are carried out on TM50 alloy. The alloy of φ7.0mm is treated by solution and aging, the tensile properties and elastic modulus are tested at room temperature, the tensile specimen are analyzed by means of OM and TEM. The bar which is drawn by 20% to 80% is aged at different temperature and then the tensile properties and elastic modulus are tested at room temperature following by OM and TEM analysis.The conclusion as following can be draw: There is twinning when the alloy is drawn by 20% through cold drawing. While the tensile strength increases by 31% from 650MPa to 857MPa after being annealed. When the rate of cold deformation is more than 20%, the main deformation is the slip of dislocations and the strength increases slowly. When the rate of cold deformation is up to 80%, the plasticity of the alloy is good and the elongation is about 10%.The β phase stable element Nb, which lowers the data of Ms of Ti-25Nb-25Zr alloy, prevents a" phase from producing. When the solution temperature is above β phase transformation point, there is complete β phase without martensitic phase and thestrength and elastic modulus is lower. When the alloy is aged between 300°C and 350°C after solution, the co phase that is rigid and fragile separates out, which will result in higher tensile strength and lower plasticity. When the alloy is aged between 400"C and 450°C, a phase separates out. Comparing with the alloy aged between 300°C and 3 50 °C,the alloy exhibits lower strength, higher plasticity and lower elastic modulus. When the alloy is aged at 500"C for 4 hours, the tensile strength decreases to 645MPa, and there is no effect of hardening. The alloy exhibits good toughness, plasticity and low elastic modulus when it is aged between 400"C and 450°C for 4 to 10 hours.The twinning and strain produced by the cold deformation will accelerate the separation of secondphase during the aging treatment. When the alloy is aged between 450°C and 500°C for 4 hours, it exhibits good toughness, plasticity and low modulus. While the shape of excluded phase and residual stress caused by cold deformation will contribute much to the properties of the alloy. There is no effect of aging hardening when the aging temperature is over 550°C, and the residual stress caused by cold deformation disappears. As will be readily seen, aging treatment after cold deformation will accelerate the hardening of the alloy and make sure higher strength, better plasticity and lower elastic modulus. Comparing with solution and aging heat treatment, this method of heat treatment will have better foreground to TM50 alloy. When the alloy, which is deformed by 20% to 80%, is aged at 550 °C, it restores and recrystallizates without secondphase. The strength of the alloy is the same as the the strength of the alloy which is annealed. The alloy recrystallizates at 550°C when the rate of cold deformation is over 40%.
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