Effects of Silicon and Heat-Treatment on Microstructure and Mechanical Properties of Biomedical Ti-39Nb-6Zr Alloy

Ji-Hoon Jang,Dong-Geun Lee

doi:10.3390/met11020268

Abstract

The cytotoxic tissue reactions of alloying elements (Al, V) of Ti-6Al-4V have been reported, whereas the Ti-39Nb-6Zr (TNZ40) alloy developed by adding β-phase stabilizing elements is known to have no cytotoxicity and exhibits excellent biocompatibility. In addition, there is a slight modulus difference between the TNZ40 alloy and human bones as the elastic modulus of the TNZ40 alloy is very low. This can inhibit detrimental effects such as osteoblast loss due to a stress-shielding effect. In this study, various Si contents were added and heat treatment under various conditions was performed to control the microstructure and mechanical properties of the TNZ40 alloy. In the β-type titanium alloy, the ω phase is commonly observed by quenching from the solution-treatment or aging-treatment temperature. These ω precipitates can typically increase the elastic modulus, hardness, and embrittlement of the β-type titanium alloy, which are important to control this phase. The correlation between Si content and precipitation and the effects of solution treatment and aging condition on the mechanical properties such as tensile strength, and hardness, were analyzed.

Highlights

Effects of Silicon and Heat-TreatmentTitanium and its alloys are generally used as high-value-added materials in the transportation equipment sector due to their excellent specific strength and corrosion resistance.They are used in medical implants due to their superior biocompatibility [1,2]
Microstructures of the Ti-39Nb-6Zr (TNZ40) alloys were observed using the OM to investigate their evolution with various Si contents and heat-treatment conditions
Because the specimen containing 0.1% Si was mainly reinforced by the ω phase, rather than the effect of precipitation hardening by Ti silicides with the addition of Ti, the ultimate tensile strength (UTS) decreased due to a reduction in the fraction of the ω phase precipitation by Si

Summary

Introduction

Titanium and its alloys are generally used as high-value-added materials in the transportation equipment sector due to their excellent specific strength and corrosion resistance. They are used in medical implants due to their superior biocompatibility [1,2]. Bones are not stimulated by the stress-shielding effects due to the application of implants with high elastic modulus; bones may deteriorate gradually, resulting in diseases such as osteoporosis [7]. As the difference between the elastic moduli of human bone and the TNZ40 alloy (~40 GPa in the case of β single phase [9]) is very small, the damage caused by the stress-shielding effects can be minimized. The correlation between the precipitation and Si content and the effects of heat-treatment conditions on the mechanical properties such as elastic modulus, hardness, and tensile strength are analyzed

Experimental

Variation of Microstructural Characteristics

Effect of Si Content

Variation of Mechanical Properties

Conclusions