Effect Of Aging Treatment On Mechanical Properties Of Ti2448 Alloy

Titanium alloy with high specific strength,excellent corrosion resistance and excellent biocompatibility has become the mainstream material in the field of biomaterials,and has great development potential.As a new medical material,Ti2448 alloy(Ti-24Nb-4Zr-8Sn)has much lower elastic modulus than other medical titanium alloy,can effectively reduce the stress shielding effect,does not contain toxic elements,has good corrosion resistance and excellent biocompatibility.In this paper,the hot-rolled Ti2448 alloy is taken as the research object,and the aging treatment is carried out to study the effect of aging treatment on the properties of Ti2448 alloy,in order to obtain more excellent medical materials.The aging treatment of hot rolled β-titanium alloy Ti2448 bar was carried out in different temperature and time.The treatment temperature was 450℃-525℃,and the aging time was 0.5h-4h.The tensile test,modulus measurement and structure observation were carried out on the treated alloy to observe the relationship between strength and modulus and aging treatment,and to explore the relationship between other mechanical properties such as strength modulus ratio and aging treatment.Take the alloys with the aging treatment of 500℃(0.5h,2h,4h)to carry out the fatigue experiment,study the influence of aging treatment on the fatigue performance of Ti2448 alloy,observe the fracture morphology and analyze the size effect of the fatigue performance of the alloy.The conclusion is as follows:After aging treatment,the strength and modulus of Ti2448 alloy increased greatly,the tensile strength increased to 1000MPa-1200MPa,and the young’s modulus increased to 70GPa-80GPa.With the increase of aging temperature,the strength of Ti2448 alloy decreases slightly,Young’s modulus changes little,the ratio of strength to modulus decreases,the phase composition is mainly α+β phase,α phase grows up with the increase of temperature,the total amounts are basically the same;with the increase of aging time,the strength of Ti2448 alloy increases,Young’s modulus also increases,the change rule of strength modulus ratio is not obvious,and the phase group The formation of a phase is mainly α+β phase,α phase increases with the increase of aging time,and the size of micro structure is basically unchanged,but at the early stage of aging,a part of interlaced lamellar structure can be seen.When other factors are excluded,the mechanical properties of the alloy are only related to the phase structure.When the fine a phase grows up,the strength of the alloy decreases,the modulus changes little,the precipitation amount of a phase increases,the strength of the alloy increases,and the modulus increases.It is speculated that the a phase nucleates on the α"phase,and then grows into lamellae from strip shape.After aging treatment,the fatigue strength of Ti2448 alloy increased to 720MPa～760MPa,and the properties of Ti2448 alloy changed greatly in the early stage of aging,and then tended to be gentle.The difference of fatigue properties between Φ3mm andΦ5mm Ti2448 alloy aged at 500℃ for 2 hours was about 20MPa,the results show that the size has little effect on the fatigue properties of the alloy.The fracture analysis of fatigue samples shows that there is only one fatigue crack source in the process of tension-tension fatigue of Ti2448 alloy aged at 500℃ for 0.5h and 4h.The cracks are generated on the surface of the sample,propagate to the interior,and then fracture to a certain extent,resulting in a large number of dimples.