| Titanium alloy has become one of the important biomedical metal materials because of its low elastic modulus,high strength and strong corrosion resistance.The use of titanium alloys to replace a large number of stainless steels can reduce the "stress shielding" effect of implants in service in vivo,so it has a broad application prospect in medical fields such as orthopedics and dentistry.This article takes the biomedical TLM(Ti-25Nb-3Mo-3Zr-2Sn)alloy as the research object,uses DEFORM software to simulate the thermal drawing process of the wire,and studies the influence of the process parameters on the thermal drawing process.The hot-drawn wire was treated by solution treatment to study the evolution of microstructure at different solution temperatures.By analyzing the simulation results(equivalent stress field,equivalent strain field and temperature field,etc.)under different processes,it is found that different process parameters have different effects on the hot drawing process.The reduction of the strain and friction coefficient and the increase of the drawing temperature will greatly reduce the drawing force.The reduction of the drawing speed and the increase of the mold temperature have a limited effect on the drawing force,and the decrease is small,but the drawing When the drawing speed exceeds 90mm/s,the local equivalent strain rate is as high as 55.7 S-1,which increases the risk of breaking during the wire drawing process.The increase of the half-cone angle makes the nonuniformity of wire deformation increase.Since each pass will cause deformation nonuniformity,the thermal deformation of multiple passes causes the degree of deformation non-uniformity to be gradually accumulated.According to the simulation results,the hot drawing process parameters of TLM titanium alloy wire are determined as: drawing speed,strain amount,friction coefficient,drawing temperature,mold temperature and half cone angle are 30mm/s,0.236,0.05,750?,300? and 10°,successfully prepared high-quality titanium alloy wire.The structure properties of the hot-drawn wire were studied.It was found that the TLM wire in the hot-drawn state was mainly composed of ? phase,and there was a small amount of ?? precipitation phase,TD-ND(Transverse direction-Normal direction)cross section The grain size of the cross section is basically the same as that of RD-ND(Rolling direction-Normal direction),and the strong thermal deformation makes the wire grains fragment.The texture of the hot-drawn state is <101>//RD,<111>/ /TD and <111>,<001>//ND.The tensile modulus of elasticity in the hot-drawn state is 30 GPa,the tensile yield strength is 800 MPa,the tensile elongation is 10%,the compressive strength is 2000 MPa,TLM alloy is added A variety of corrosion-resistant elements of Nb,Mo,Zr and Sn can be formed,which can easily form a stable passivation film,so it has good corrosion resistanceThe heat-drawn wire was subjected to solution treatment at 600°C,670°C and 740°C.It was found that the wire treated at 600°C and 670°C was composed of ? phase,needle-like ? phase and ?? phase,The ? phase and the ?? phase cross each other and penetrate the grain.With the increase of the solution temperature,the degree of recrystallization gradually increases,the ? grains gradually grow,and the grain boundaries appear polygonal.<101> and <100> are the preferred growth directions of the recrystallized grains.The recrystallization texture is <101>//RD. |
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