Effect Of Alloying Elements On Mechanical Properties Of TiZr Alloy

TiZr binary alloy has recently been studied as a new dental implant material because it possesses superior mechanical properties compared with the traditional pure titanium as implant and almost identical osseointegration capacity as pure titanium.However,there are few reports in the literature on the mechanical properties of TiZr alloy with the respects to the thermal mechanical processing and the composition optimization of the alloy.In the present study,the TiZr alloys with zirconium content of 12-20% and oxygen content of less than 0.3% were melt.The recrystallization behavior was systematically studied.The tensile strength and tensile elongation,and their dependence on the Zr and O concentration were evaluated.The results of recrystallization process showed that:(1)the TiZr alloys always transformed to α’ martensite after solid solution treatment in the β phase zone,no matter it was quenched or furnace cooled to room temperature,and the α’ martensite is reluctant to recrystallized to the equiaxed α grains by simple annealing treatment in the temperature region of α phase.The fully recrystallized equiaxed α grain microstructure was obtained only after repeated hot roolling + long time α recrystallization anealing;(2)The recrystallization of the alloys becomes more difficult with the increase of zirconium and/or oxygen concentration,and consequently much long annealing time was needed to reach full recrystallization;(3)The fully recrystallized and then cold rolled samples of 60% thickness reduction were readily recrystallized after annealing at 700°C for 0.5 h,and a fine equiaxed α grain microstructure can be obtained.The results of the element content on mechanical properties shown that:(1)The solid solution strengthening rate of Zr and O elements was about 8MPa/1wt% and about 100MPa/0.1wt% of tensile strength,respectively,as measured with fully recrystallized specimens;(2)The cold rolled samples can achieve high tensile strength and the strength decreased with the increasing annealing temperature;(3)The oxygen content has particular influence on the plasticity of the alloy.The tensile elongation of the alloy was almost not affected when the oxygen is below 0.2%,while the elongation of the alloy decreases sharply as the oxygen content further approaches to 0.3%.