HATi/Ti/HATi轴对称生物功能梯度材料的制备及其热应力缓和特性

PREPARATION AND THERMAL STRESS RELAXATION CHARACTERISTICS OF HA Ti/Ti/HA Ti AXIAL SYMMETRICAL FUNCTIONALLY GRADED BIOMATERIAL

用粉末冶金法制备出ＨＡＴｉ／Ｔｉ／ＨＡＴｉ 轴对称生物功能材料（ＦＧＭ） ， 并测定了ＨＡＴｉ 复合体材料的力学性能和热膨胀系数。应用经典叠层板理论和热弹性力学理论分析了ＨＡ４０Ｔｉ／Ｔｉ／ＨＡ４０Ｔｉ 直接叠层体和轴对称ＦＧＭ 制备残余热应力。结果表明其微观组织呈对称型梯度化分布。ＦＧＭ 中间纯Ｔｉ 层具有最高的抗弯强度和断裂韧性（ 分别为９７１ ．９６ ＭＰａ 和２９ ．６９１ ＭＰａ·ｍ １／２） ， 而表面层的弹性模量最低， 只有８７ ．７１ ＧＰａ。从生物医学应用的角度看， 力学性能如此分布的生物材料正是我们所期望的。其热膨胀系数随着ＨＡ 含量和温度的升高而增大。制备残余热应力强烈依赖于组成分布，组成对称梯度化分布导致了ＦＧＭ 中残余热应力也呈现对称梯度化分布， 并降低了其表面层制备残余拉应力。

The hydroxyapatite(HA) Ti/Ti/HA Ti axial symmetrical functionally graded biomaterial (FGM) has been developed by powder metallurgical process. Mechanical properties and thermal expansion coefficient of HA Ti composite materials were investigated. The residual thermal stress in axial symmetrical FGM and HA40 Ti/Ti/HA40 Ti non FGM plate cooled to room temperature after sintering has been analyzed by the classical lamination theory and thermal elastic mechanics. The results showed that the microstructure of FGM displays a symmetrical graded distribution; the middle pure Ti layer in FGM has the maximal bending strength and fracture toughness(971.96 MPa and 29.69 MPa·m 1/2 respectively), while the Young's modulus of surface layer (only 87.71 GPa) is minimal, the biomaterial with such a distribution of mechanical properties is expected from the viewpoint of bio applications. The thermal expansion coefficient increases with the rise of the testing temperature and HA content; the residual thermal stress strongly depends on the constitutional distribution. The graded distribution of the compositions results in the decrease of residual tensile stress in surface layer. The residual thermal stress in FGM exhibits the axial symmetrical graded distribution as the compositions.