导　　师： 杨贤金

学科专业： 080502

授予学位： 硕士

作　　者： ;

机构地区： 天津大学

摘　　要： 基于钛合金的d电子设计理论/(DV-Xα分子轨道理论/),本文设计一种成分为Ti-22Nb-4Zr-2Sn/(at/%/)的稳定β型钛合金。采用冷坩埚感应熔炼的方法制备合金铸锭,经过热锻、热处理、冷轧和不同温度退火等工艺过程,采用X射线衍射/(XRD/)和金相组织观察对合金的相变特点进行研究;采用弯曲法测试合金的超弹性和形状记忆效应;采用静载拉伸法测试合金的拉伸性能。 这种合金在室温下具有稳定的β相。热锻后经850℃保温0.5小时后淬火的合金能够冷轧90/%而没有裂纹产生。冷轧产生的缺陷和内应力促进退火过程中的β→α转变。少量的α相的产生能够促进淬火过程中马氏体α”的形成,过多的α相则抑制α”的相产生。 合金冷轧形成{100}<011>织构,低温退火强化{100}<011>织构;高温退火产生再结晶,再结晶织构为{112}<110>。弯曲实验表明合金具有良好的弹性和较低的形状记忆效应:300℃退火1小时后的合金在加载弯曲变形量6.5/%时具有3.88/%的弹性回复;800℃退火1小时后的合金具有最大形状记忆效应,形状记忆回复变形量为0.34/%。热处理后合金的屈服强度高于500MPa;弹性模量在20～35GPa之间。热处理过程中产生的α相和ω相影响合金的力学性能、超弹性及形状记忆效应。 采用仿生生长的方法能够使合金表面生长一层以羟基磷灰石/(HA/)为主的钙磷涂层,从而进一步改善合金的生物相容性。 Based on the d-electron alloy design theory /(DV-Xαmolecular orbital method/) for titanium alloys, a beta type titanium alloy Ti-22Nb-4Zr-2Sn/(at/%/) was designed. The ingot was prepared by cold crucible induction melting, then it was hot-forged, heat-treated, cool-rolled and annealed in turn at different temperatures. Phase transformation characters were analysed by using X-ray diffraction /(XRD/) and optical microscope. The superelastic and shape memory effect of the alloy were measured by bending test, and the tensile property was tested by static stretching. The results show that the microstructure of the alloy is stable phaseβat room temperature. Hot-forged alloy was heated at 850℃for 0.5 hour and water quenched, then it could be cool rolled with reduction of 90/% without any crack. Defects and inner stess promoteβ→αtransformation during annealing. Small amount ofαphase precipitate acceleratesα”martensite formation during quenching, while overfullαphase has a opposite action. A kind of {100}<011> texture was formed during cool rolling, and it was strengthened when annealing at low temperature. Another kind of {112}<110> recrystallization texture was developed after annealing at high temperature. A good superelastic property and weak shape memory effect were observed through bending test. The alloy annealed at 300℃for 1 hour exhibited a maximum recovery strain about 3.88/% when uploaded strain was 6.5/%. The alloy annealed at 800℃for 1 hour showed a maximum shape memory effect, but its recovery strain was only 0.34/%. The yield stress of alloy was over 500MPa, and its Young’s modulus was between 20 and 35 GPa after heat treatment. Theαandωphases which formed during heat-treatment had influence on the mechanical property, superelastic and shape memory effect. Expected performance of the alloy could be obtained by heat treatment. A Ca-P layer, primarily consisted of Hydroxyapatite /(HA/), could be prepared on the surface of alloy by bio-mimetic growth, which could further imp

关 键 词： 型钛合金 生物医用材料 显微组织 力学性能 超弹性

领　　域： [金属学及工艺] [一般工业技术] [金属学及工艺]