ADVANCED ENGINEERING MATERIALS Dol:10.1002/adem.200800026 Nanostructured Titanium for Biomedical Applications By Ruslan Z.Valliev,Irina P.Semenova,Vladimir V.Latysh,Henry Rack,Terry C.Lowe,Jiri Petruzelka, Ludek Dluhos,Daniel Hrusak and Jarmila Sochova Metallic materials,for example,stainless steel,titanium avenues and concepts for medical implants,providing bene- and its alloys,and tantalum,are widely used for medical im- fits in all areas of medical device technology plants in trauma surgery,orthopedic and oral medicine.-31 Numerous clinical studies of medical devices fabricated Successful incorporation of these materials for design,fabri- from commercial purity (CP)titanium for trauma,orthopae- cation and application of medical devices require that they dic and oral medicine has proven its excellent biocompatibil- meet several critical criteria.Paramount is their biocompat- ity.However the mechanical strength of CP titanium is rela- ibility as expressed by their relative reactivity with human tis- tively low compared to other metals used in biomedical sues.Another is their ability to provide sufficient mechanical devices.Whereas the strength of this material can be in- strength,especially under cyclic loading conditions to ensure creased by either alloying or secondary processing,for exam- the durability of the medical devices made therefrom.Finally ple rolling,drawing,etc.,these enhancements normally come the material should be machinable and formable thereby en- with some degradation in biometric response and fatigue be- abling device fabrication at an affordable cost.In this paper haviour.Recently it has been shown that nanostructuring of we show that nanostructured commercial purity titanium CP titanium by SPD processing can provide a new and prom- produced by severe plastic deformation (SPD)opens new ising alternative method for improving the mechanical prop- erties of this material This approach also has the benefit of enhancing the biological response of the CP titanium sur- face,I91 This paper reports the results of the first developments [*Prof.R.Z.Valiev,Dr.I.P.Semenova and studies of nanostructured titanium (n-Ti),produced as Institute of Physics of Advanced Materials long-sized rods with superior mechanical and biomedical Ufa State Aviation Technical University properties and demonstrates its applicability for dental im- 12 K.Marx str.,Ufa 450000 Russia plants.The effort was conducted using commercially pure E-mail:RZValiev@mail.rb.ru Grade 4 titanium [C-0.052%,O2-0.34%,Fe -0.3%,N- Dr.V.V.Latush 0.015%,Ti-bal.(wt.pct.)].Nanostructuring involved SPD Innovation Scientific and Technical Center skra> processing by equal-channel angular pressinglol followed by 81 Pushkin str. thermo-mechanical treatment(TMT)using forging and draw- Ufa 450077 Russia ing to produce 7 mm diameter bars with a 3 m length.This Prof.H.Rack processing resulted in a large reduction in grain size,from School of Materials Science and Engineering the 25 um equiaxed grain structure of the initial titanium rods Clemson University to 150 nm after combined SPD and TMT processing,as Clemson,SC 29634 LISA shown in Figure 1.The selected area electron diffraction pat- Dr.T.C.Lowe tern,Figure 1(c),further suggests that the ultra fine grains Los Alamos National Laboratory contained predominantly high-angle non-equilibrium grain Los Alamos boundaries with increased grain-to-grain internal stresses.1 NM 87545 USA A similar structure for CP Ti can be produced in small Prof.J.Petruzelka discs using other SPD methods,for example-high pressure FS,VSB-Technicki univerzita Ostrava torsion(HPT)as studied in detail.s In the present work it tr.17 listopadu 15 was essential to produce homogeneous ultrafine-grained Ostrava-Poruba,CZ 708 33 structure throughout a three-meter length rod to enable the E-mail:jiri.petruzelka@vsb.cz pilot production of implants and provide sufficient material J.Sochova,Dr.L.Dluhos for thorough testing of the mechanical and bio-medical prop- Timplant,Sjednoceni77 erties of the nanostructured titanium. Ostrava-Polanka,CZ 725 25 Table 1 illustrates mechanical property benefits attainable Dr.D.Hrusak by nanostructuring of CP titanium,for example,the strength FN Plzen of the nanostructured titanium is nearly twice that of conven- Alej Svobody 80 tional CP titanium.Notably this improvement has been Plzen CZ 323 00-Czech Republic achieved without the drastic ductility reductions (to below WY InterScience ADVANCED ENGINEERING MATERIALS 2008,10,No.8 2008 WILEY-VCH Verlag GmbH Co.KGaA,WeinheimDOI: 10.1002/adem.200800026 Nanostructured Titanium for Biomedical Applications By Ruslan Z. Valiev,* Irina P. Semenova, Vladimir V. Latysh, Henry Rack, Terry C. Lowe, Jiri Petruzelka, Ludek Dluhos, Daniel Hrusak and Jarmila Sochova Metallic materials, for example, stainless steel, titanium and its alloys, and tantalum, are widely used for medical im￾plants in trauma surgery, orthopedic and oral medicine.[1–3] Successful incorporation of these materials for design, fabri￾cation and application of medical devices require that they meet several critical criteria. Paramount is their biocompat￾ibility as expressed by their relative reactivity with human tis￾sues. Another is their ability to provide sufficient mechanical strength, especially under cyclic loading conditions to ensure the durability of the medical devices made therefrom. Finally the material should be machinable and formable thereby en￾abling device fabrication at an affordable cost. In this paper we show that nanostructured commercial purity titanium produced by severe plastic deformation (SPD) opens new avenues and concepts for medical implants, providing bene￾fits in all areas of medical device technology. Numerous clinical studies of medical devices fabricated from commercial purity (CP) titanium for trauma, orthopae￾dic and oral medicine has proven its excellent biocompatibil￾ity.[3] However the mechanical strength of CP titanium is rela￾tively low compared to other metals used in biomedical devices. Whereas the strength of this material can be in￾creased by either alloying or secondary processing, for exam￾ple rolling, drawing, etc., these enhancements normally come with some degradation in biometric response and fatigue be￾haviour. Recently it has been shown that nanostructuring of CP titanium by SPD processing can provide a new and prom￾ising alternative method for improving the mechanical prop￾erties of this material.[4–8] This approach also has the benefit of enhancing the biological response of the CP titanium sur￾face.[9] This paper reports the results of the first developments and studies of nanostructured titanium (n-Ti), produced as long-sized rods with superior mechanical and biomedical properties and demonstrates its applicability for dental im￾plants. The effort was conducted using commercially pure Grade 4 titanium [C – 0.052 %, O2 – 0.34 %, Fe – 0.3 %, N – 0.015 %, Ti-bal. (wt. pct.)]. Nanostructuring involved SPD processing by equal-channel angular pressing[10] followed by thermo-mechanical treatment (TMT) using forging and draw￾ing to produce 7 mm diameter bars with a 3 m length. This processing resulted in a large reduction in grain size, from the 25 lm equiaxed grain structure of the initial titanium rods to 150 nm after combined SPD and TMT processing, as shown in Figure 1. The selected area electron diffraction pat￾tern, Figure 1(c), further suggests that the ultra fine grains contained predominantly high-angle non-equilibrium grain boundaries with increased grain-to-grain internal stresses.[11] A similar structure for CP Ti can be produced in small discs using other SPD methods, for example – high pressure torsion (HPT) as studied in detail.[8] In the present work it was essential to produce homogeneous ultrafine-grained structure throughout a three-meter length rod to enable the pilot production of implants and provide sufficient material for thorough testing of the mechanical and bio-medical prop￾erties of the nanostructured titanium. Table 1 illustrates mechanical property benefits attainable by nanostructuring of CP titanium, for example, the strength of the nanostructured titanium is nearly twice that of conven￾tional CP titanium. Notably this improvement has been achieved without the drastic ductility reductions (to below COMMUNICATIONS ADVANCED ENGINEERING MATERIALS 2008, 10, No. 8 © 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim 1 – [*] Prof. R. Z. Valiev, Dr. I. P. Semenova Institute of Physics of Advanced Materials Ufa State Aviation Technical University 12 K. Marx str., Ufa 450000 Russia E-mail: RZValiev@mail.rb.ru Dr. V. V. Latysh Innovation Scientific and Technical Center «Iskra» 81 Pushkin str. Ufa 450077 Russia Prof. H. Rack School of Materials Science and Engineering Clemson University Clemson, SC 29634 USA Dr. T. C. Lowe Los Alamos National Laboratory Los Alamos NM 87545 USA Prof. J. Petruzelka FS, VŠB – Technická univerzita Ostrava tr. 17 listopadu 15 Ostrava-Poruba, CZ 708 33 E-mail: jiri.petruzelka@vsb.cz J. Sochova, Dr. L. Dluhos Timplant®, Sjednocení 77 Ostrava – Polanka, CZ 725 25 Dr. D. Hrusak FN Plzen Alej Svobody 80 Plzen CZ 323 00 – Czech Republic