Ultrasonic Nondestructive Evaluation Of Elastic Property For Titanium Alloys With Low Elastic Modulus For Biomedical Application

The research of new titanium alloy for biomedical application with non-toxic elements and low elastic modulus has been focused. In order to meet the standard of biomedical material, it is required to increase the strength and decrease the elastic modulus of the alloy to get the best strength-elasticity ratio. This article investigated the variation of elastic property from the heat treatment and alloying element content. The ultrasonic longitudinal and shear velocities of Ti-Nb-Zr alloy were measured by water immersion focusing method and longitudinal grazing incidence method. Based on the christoffel equation, elastic parameters were calculated. The relationship between the elastic property and ultrasonic parameters was analyzed combining with the results of X-ray diffraction and metallographic.The elastic modulus of titanium alloy were measured by ultrasonic velocity method and compared with this obtained by means of tensile method. It is found that these two methods showed comparable results, the changing range is only 3.6%, which indicated that it is feasible to evaluate the elastic property of titanium alloy with low elastic modulus by ultrasonic velocity method.Effect of aging temperature on the elastic modulus of Til8Nb7Zr and Ti27Nb8Zr were investigated. In view of the intimate correlation between microstructure and elastic property, the reasons that caused the change of elastic parameters were analyzed and discussed further on the microstructure point of view. The results of Til8Nb7Zr showed that with much higher aging temperature, velocities and elastic modulus increased, whereas, Poisson's ratio decreased. It is thought that the varied elastic modulus is closely related to the transformation from lamellarβ+a phase to dispersed a phase and B phase. Meanwhile, the results of Ti27Nb8Zr showed that velocities and elastic modulus decreased with increasing aging temperature, while Poisson's ratio elevated. It is considered through analysis that martensite obtained by solution treatment decomposed phases with various morphology and content at different aging temperature, which induced the change of elastic modulus.The ultrsonic velocities of Ti-xNb-7Zr alloy with the Nb content of 15%-30% were measured and the elastic modulus were deduced. With the increasing of Nb content, the velocities and elastic modulus gradually increased and reached the maximum value when Nb content is 24%, then presented the trend of decrease. It is considered to relate with the volume fractions and elastic modulus ofβand a".The attenuation coefficient of Ti-xNb-7Zr alloy was calculated by spectrum analysis, the results presented the general trend of increase, but declined when the Nb content is 27%. There are many reasons for the changes of attenuation coefficient. It is the combined results of velocity, density, elastic property et al. Therefore, it is difficult to analyze quantitatively. At present, it can only carry on qualitative analysis to the results.