RU2777089C2 - Three-component alloys ti-zr-o, their production methods and their corresponding applications - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: invention relates to the field of metallurgy, namely to a three-component alloy of titanium-zirconium-oxygen; it can be used in medicine, in the transport industry, or in the energy industry. The three-component alloy of titanium-zirconium-oxygen (Ti-Zr-O) contains from 83 to 95.15 wt.% of titanium, from 4.5 to 15 wt.% of zirconium, and from 0.35 to 2 wt.% of oxygen, wherein it is capable of forming single-phase material consisting of a stable and homogenous α-solid solution with a structure of a hexagonal tightly packed (HTP) grate at a room temperature. A method for thermomechanical processing of the alloy of titanium-zirconium-oxygen (Ti-Zr-O) includes cold processing of the alloy in a recrystallized state at a room temperature with a pressing degree from 40 to 90%. In addition, thermal processing can be conducted at a temperature from 500 to 650°C during a time from 1 to 10 min.

EFFECT: high values of strength and plasticity of an alloy are provided, as well as excellent biocompatibility of the alloy.

14 cl, 7 dwg

Description

FIELD OF TECHNOLOGY

[0001] The invention relates to the field of titanium-based alloys and more specifically to three-component alloys of this type. The invention relates to titanium-zirconium-oxygen alloys, as well as methods for their production and their thermomechanical processing.

PRIOR ART

[0002] Titanium and its alloys have been the subject of particular attention due to their mechanical and biomechanical properties, especially their high mechanical strength, corrosion resistance, and biocompatibility.

[0003] Materials Science and Engineering C, September 28, 2013, p. 354-359 discloses the effect of zirconium concentration on the properties of Ti-Zr alloys and specifically notes the lack of cytotoxicity noted with such elements.

[0004] In addition, the article "Mechanical properties of the binary titanium-zirconium alloys and their potential for biomedical materials", published in the "Journal of Biomedical Materials Research)), volume 29, pages 943-950, in 1995, gives an idea on the state of research at that time on the mechanical properties of titanium-zirconium alloys and their possible application as a biomedical material.

[0005] In addition, document FR 3037945 is known, disclosing a method for producing a titanium-zirconium composite material, more specifically in which the starting material is nanometer-scale zirconia powder, by additive manufacturing, such a process provides the correct control of geometry, porosity and interconnectedness; for this reason he was chosen. The resulting product is actually a composite material with a metal matrix and ceramic reinforcement (oxide particles). It is preferably used as a dental and/or surgical implant. Such an alloy, however, does not meet all the requirements for this application. As explained in more detail below, the starting materials used, the disclosed method and the resulting material differ from the purpose of the present invention.

[0006] The most commonly used alloy in dental implantology is TA6V (actually Ti-6Al-4V in wt %), which composition includes aluminum and vanadium, the long-term toxicity of which is increasingly suspected in the scientific community and public health services. At that time, such an alloy was chosen because of the interesting combination of its mechanical properties. After some time, in the light of accumulated practical experience, such an alloy began to cause distrust among implant manufacturers, who now want to replace it.

[0007] Patent EP 0988067 B1 is also known, disclosing a two-component titanium-zirconium alloy containing both of these alloy components, as well as up to 0.5 wt. % hafnium, and hafnium is an impurity contained in zirconium. This alloy contains approximately 15 wt. % zirconium, and the oxygen content is from 0.25 to 0.35 wt. %. Implants made from this alloy have good mechanical properties, but are not superior to those of the TA6V alloy.

[0008] In addition, commercially pure grade 3 or 4 titanium enriched in oxygen to 0.35% is used. Such a material is ideally biocompatible, but its mechanical properties remain insufficient. More specifically, it can be noted that the mechanical strength of this type of titanium is at least 300 MPa lower than that of TA6V. Recently, the mechanical strength of pure titanium has been further improved by working with cold-worked material resulting in additional hardening. The mechanical strength of this type of material is improved compared to industrial annealed titanium. However, this result is achieved at the expense of its plasticity.

[0009] At present, it seems important to create alternative alloys that have both optimized biocompatibility and a combination of mechanical properties that are superior to those of known materials. In addition, a simple production method is desirable.

BRIEF DESCRIPTION OF THE INVENTION

[0010] the Invention is directed to eliminate the disadvantages of the prior art and specifically to provide an alloy that combines excellent biocompatibility and coupled properties of high mechanical strength and high ductility.

[0011] For this purpose and in accordance with the first aspect of the invention proposed a three-component titanium-zirconium-oxygen (Ti-Zr-O) alloy, which contains from 83 to 95.15 wt. % titanium, from 4.5 to 15 wt. %. zirconium and from 0.35 to 2 wt. % oxygen, and said alloy is capable of forming a single-phase material consisting of a stable and homogeneous α-solid solution of a hexagonal close-packed (hcp) structure at room temperature.

[0012] In other words, the invention relates to a new family of three-component alloys, where oxygen is considered as a full element of the alloy, i.e. added in a controlled manner; such titanium-based alloys of the Ti-Zr-O type having a high oxygen content (greater than 0.35 wt %) combine excellent biocompatibility with the associated properties of high strength and high ductility. Oxygen in this case is deliberately added in a controlled manner to obtain a ternary Ti-Zr-O alloy forming a stable and homogeneous α-solid solution at room temperature. In this alloy, oxygen is a true element of the alloy in the sense that it is not considered as an impurity, as may be the case in the prior art. According to the invention, oxygen is added during a solid phase process, ie using powder particles of TiO ₂ or ZrO ₂ oxides in controlled amounts, in a production method by melting an alloy.

[0013] More specifically, in the case of an alloy containing 0.60% oxygen and 4.5% zirconium, the alloy in accordance with the present invention may have, in a recrystallized state, a mechanical strength of approximately 900 MPa associated with a ductility of more than 30%; this surpasses the properties of the known TA6V alloy.

[0014] Advantageously, the ternary alloys of the Ti-Zr-O family are single-phase materials regardless of temperature (up to temperatures close to the beta transition temperature). As a consequence, the materials of the invention are not very sensitive in terms of microstructure gradients. Thus, a decrease in dispersion is expected with respect to the properties of the final product; and moreover, it is preferably biocompatible.

[0015] The invention further relates to a thermomechanical processing method for producing a ternary Ti-Zr-O alloy. The invention proposes a method for producing a three-component Ti-Zr-O alloy, in which the starting product is the specified alloy in a recrystallized state, which is then subjected to cold working at room temperature in the first stage in order to increase its mechanical strength. An increase in strength of about 30% is expected, combined with a loss of ductility. "Room temperature" means a temperature of about 25°C.

[0016] Preferably, the cold working is cold rolling.

[0017] A reduction ratio of 40% to 90% is preferably used during the cold working step (eg, cold rolling).

[0018] In addition, the method is directed to performing the second step, i.e. heat treatment, which consists in heating the cold-worked alloy at a temperature of from 500 to 650°C for a time of 1 to 10 minutes in order to restore the ductility of the specified alloy while limiting decrease in its mechanical strength. The goal is to maintain a high level of mechanical strength.

[0019] The heat treatment in the second step is also referred to as "instant treatment" in the context of this description.

[0020] More specifically, the alloys according to the invention, after appropriate thermomechanical treatment, have a yield strength greater than or equal to 800 MPa.

[0021] In addition, the alloys according to the invention, after appropriate thermomechanical treatment, have a tensile strength (UTS) of about or greater than 900 MPa.

[0022] The alloys of the invention, after appropriate thermomechanical treatment, have an overall ductility of about 15% or more.

[0023] In addition, the invention relates to the use of such an alloy in the medical, transport or energy fields. The invention is preferably applied to the production of dental implants. Other applications are possible and promising in the field of orthopedics; the advantages of the invention can be used in maxillofacial surgery, the production of various medical devices, as well as in the transport industry, more specifically the aerospace industry, and energy, in particular, but not exclusively, in the field of nuclear research or chemistry in a broad sense, can find application for the present invention.

[0024] The invention is further directed to the additive manufacturing of alloys, since the alloys of the invention are not subject to the often observed microstructural gradients, as they are single-phase and homogeneous in terms of microstructure and chemistry.

BRIEF DESCRIPTION OF GRAPHICS

[0025] Additional features and advantages of the invention will become apparent upon reading the following description, made with reference to the accompanying figures, which show:

- in Fig. 1 schematically shows the basic structure of a ternary Ti-Zr-O alloy according to the first embodiment of the invention;

- in Fig. 2 shows a thermomechanical processing method used to modify the properties of a ternary alloy, in accordance with another embodiment of the invention;

- in Fig. 3 shows curves showing the effect of oxygen on the mechanical properties of recrystallized alloys according to the invention;

- in Fig. 4 shows curves showing the effect of zirconium on the mechanical properties of recrystallized alloys according to the invention;

- in Fig. 5 shows the effect of thermomechanical treatment (including 85% thickness reduction) on the mechanical properties of an alloy according to the invention;

- in Fig. 6 shows the effect of thermomechanical treatment (including a 40% reduction in thickness) on the mechanical properties of an alloy according to the invention; and

- in Fig. 7 compares the mechanical properties of the ternary Ti-Zr-O alloys produced in accordance with the invention with those of reference alloys.

[0026] For greater clarity, identical or similar features are indicated by the same reference symbols throughout the figures.

DETAILED DESCRIPTION OF CARRYING OUT THE INVENTION

[0027] FIG. 1 schematically shows the basic structure of a ternary alloy according to the invention obtained by solid solution solidification. The solidification of the alloy according to the invention in the recrystallized state occurs as a result of solid solution solidification of substitution (Zr) and interstitial (O). As for the occupied sites, it can be seen that in such a solid solution, the zirconium atoms occupy Ti positions in the lattice (substitution positions) and the oxygen atoms occupy interstitial positions (between the atoms of the hexagonal lattice). According to this scheme, oxygen is a reinforcing element with the properties of an interstitial element, and zirconium is a reinforcing element with the properties of a replacement element.

[0028] The invention is based on the desirable and exclusive addition of fully biocompatible alloying elements with high solid solution strengthening capability. The choice of zirconium is due to its ability to form a homogeneous solid solution with titanium at any temperature. The range in the composition (from 4.5 to 15 wt.% zirconium) was chosen so as to keep the titanium-rich alloy in order to optimize the cost of the alloys. The choice of oxygen as a valuable element of the alloy is associated with its very high ability to cure the material. Usually it is present in commercially available materials only in amounts not exceeding 0.35% (wt.%).

[0029] In contrast, and without any prejudice, in the family of alloys according to the invention, oxygen is added in a large amount (from 0.35 to 2%) and in a controlled manner in the form of a solid phase additive of a selected amount of TiO ₂ or ZrO ₂ so that after completion melting to obtain a solid solution homogeneous in terms of its composition and rich in oxygen. The resulting material is single-phase, with an alpha phase, at any temperature (up to temperatures close to the temperature of the beta transition).

[0030] In addition, as shown in FIG. 2, thermomechanical processing can be used to achieve an optimized microstructural state. An innovative sequence or series of thermomechanical treatments of alloys in accordance with the invention is proposed in order to obtain a more significant hardening. The method includes several steps, one of which is a heat treatment, which must be short (1 to 10 minutes) to obtain a reduced and non-recrystallized state. According to such processing, the raw material is in a recrystallized state (step 1), then cold working (eg, cold rolling) is performed at room temperature (step 2). The reduction ratio can be from 40 to 90% depending on the alloy in question; this stage of the method allows to increase the mechanical strength of the material. Then, preferably, a short, so-called flash heat treatment (3) is carried out, which consists in heating to a temperature of 500 to 650° C. for a period of time from one to ten minutes. The so-called "instantaneous" heat treatment makes it possible to partially restore ductility while maintaining mechanical strength higher than that of the initial recrystallized state. The material thus retains high mechanical strength and regains the ductility lost when the metal was cold worked.

[0031] Thus, the invention provides a solution relating to a three-component alloy containing an exclusively single-phase, alpha-phase, and completely homogeneous solid solution, i.e. without precipitates of another additional phase.

[0032] Various curing modes were considered in order to obtain all of these characteristics, by changing the amount of zirconium and oxygen, respectively.

[0033] As shown in FIG. 3 and 4, respectively, the effect of solute hardening, that is, using a solid solution, can be detected by performing mechanical tensile tests of new alloys in the recrystallized state. An increase in the mechanical strength of the alloy can be noted both after the addition of oxygen (Fig. 3) and after the addition of zirconium (Fig. 4).

[0034] The four curves in FIG. 3, which show the dependence of stress on the relative elongation (or tension) of the alloy in question, obtained for alloys containing 4.5% zirconium and an oxygen content of 0.35%, respectively, on curve A, 0.40% on curve B, 0.60% on curve C and 0.80% on curve D.

[0035] The three curves in figure 4, which show the dependence of stress on the elongation (or stretch) of the alloy in question, were obtained for alloys containing 0.40% oxygen and a zirconium content of 4.5% in curve B and 9% in curve C, respectively. The alloy corresponding to curve A does not contain zirconium.

[0036] The ductility in the recrystallized state remains very high in the considered composition range compared to, for example, the ductility of commercially available pure titanium (about 20%).

[0037] FIG. 5 shows the additional effect of various steps in the thermomechanical treatment sequence on the 0.4% O-4.5% Zr alloy. More specifically, the initial state is a recrystallized alloy, as shown in curve A. This alloy has high ductility, above 25%, but relatively low mechanical strength of about 700 MPa. Performing cold working (eg cold rolling) at room temperature, eg with 85% reduction in thickness (TR), allows a significant increase in mechanical strength, but in turn significantly reduces ductility. Curve B shows such a characteristic state. Curve C shows the state of the alloy after subsequent application of flash heat treatment to such a deformed state. This heat treatment makes it possible to partially restore ductility while maintaining high mechanical strength. The combined final properties obtained for an alloy containing 0.4% O and 4.5% Zr (wt.%), after cold rolling and flash working for 1 minute and 30 seconds at 500°C, are higher than the properties of the known alloy TA6V. With regard to the results corresponding to curve C, according to the invention, a mechanical strength of approximately 1100 MPa and a ductility of the order of 15% can be noted. As previously known, the mechanical strength of the TA6V alloy is about 900 MPa and the associated ductility is about 10%.

[0038] FIG. 6 shows the effect of several thermomechanical treatments on a 0.4% O-9% Zr alloy. Curve A shows the mechanical properties of the recrystallized alloy obtained after heat treatment at 750° C. for 10 minutes. Then, a thickness reduction (TR) of 40% is carried out on said alloy. Curve B refers to the cold rolled condition. "Flash" heat treatments are applied to this cold worked condition. Curve C refers to material that was heat treated at 500° C. for 150 seconds; curve D shows a material that has been heat treated at 550° C. for 60 seconds; and curve E refers to material that was heat treated at 600° C. for 90 seconds. Both recrystallized and heat treated alloys exhibit interesting mechanical properties comparable to or better than those of the known TA6V alloy.

[0039] FIG. 7 shows the superiority of several alloys according to the invention over two known alloys: TA6V and TA6V ELI. TA6V ELI is currently used in the medical field. ELI stands for Extra Low Interstitial. The TA6V specifications are shown in the top rectangle, while the TA6V ELI specifications are shown in the bottom rectangle. For each rectangle, the top level corresponds to the characteristic mechanical strength and the bottom level represents the characteristic yield strength. The width of each rectangle, equal to about 10%, corresponds to the ductility of the corresponding alloy. The four curves in FIG. 7 correspond to the alloys according to the invention. They have higher properties than TA6V - Ti Grade 5 - and TA6V ELI - Ti Grade 23. To confirm the caption to Fig. 7, curve A corresponds to a three-component alloy containing 4.5% zirconium and 0.4% oxygen, to which apply heat treatment at 500°C for 90 seconds after reducing the thickness (TR) by 85%. Curve B describes the properties of an alloy containing 0.4% oxygen and 9% zirconium, which is heat treated at 500° C. for 150 seconds after a 40% reduction in thickness; curve C shows the properties of an alloy containing 0.4% oxygen and 9% zirconium, which is heat treated at 550° C. for 60 seconds after a 40% reduction in thickness. Curve D is obtained for a recrystallized alloy containing 0.4% oxygen and 9% zirconium, this recrystallized state is obtained by heat treatment at 750°C for 10 minutes after a 40% reduction in thickness (TR). Thus, curve A in Fig. 7 is the curve labeled C in FIG. Thus, curves B, C and D in FIG. 7 are respectively the curves labeled C, D and A in FIG. 6.

[0040] With regard to the preferred method of the invention, a cold working step with a reduction ratio (or reduction in thickness TR) of 40% or more is performed on a three-component alloy as described above, and is followed by a heat treatment step at a temperature of 500 to 650° C for a period of one minute to ten minutes.

[0041] The desired and intentional presence of a controlled and high amount of oxygen in such a ternary alloy makes such an alloy novel. In addition, this goes against the grain of prejudice, since until now the presence of oxygen has been limited or uncontrolled mainly due to the impurities present in the starting material. In other words, the amount of oxygen present in known titanium alloys is usually limited to less than 0.35 wt. % and is usually the result of relative impurity in the starting materials used.

[0042] In addition, the alloys of the invention may be in bulk or powder form. In the case of an array shape, the alloys according to the invention can be presented in a wide range of products such as ingots, bars, wires, tubes, sheets and plates, and so on.

[0043] In addition, the alloys according to the invention can be easily cold worked: for example, pipes can be easily formed from such alloys. This is due to the level of ductility of the alloys according to the invention.

Claims (16)

1. Three-component alloy titanium-zirconium-oxygen (Ti-Zr-O), characterized in that it contains from 83 to 95.15 wt.% titanium, from 4.5 to 15 wt.% zirconium and from 0.35 to 2 wt.% oxygen, and the specified alloy is able to form a single-phase material consisting of a stable and homogeneous α-solid solution with a hexagonal close-packed (hcp) lattice structure at room temperature. 2. An alloy according to claim 1, characterized in that it has a yield strength greater than or equal to 800 MPa. 3. An alloy according to claim 1 or 2, characterized in that it has a tensile strength (UTS) greater than or equal to 900 MPa. 4. Alloy according to any one of paragraphs. 1-3, characterized in that it has an overall plasticity of 15% or more. 5. Alloy according to any one of paragraphs. 1-4, characterized in that it belongs to the single-phase type up to temperatures close to the temperature of the beta transition. 6. Alloy according to any one of paragraphs. 1-5, characterized in that it is biocompatible. 7. An alloy according to claim 1, which is in the form of a powder. 8. The method of thermomechanical processing of a three-component alloy titanium-zirconium-oxygen (Ti-Zr-O) according to any one of paragraphs. 1-3, characterized in that the initial product is a three-component alloy in a recrystallized state, and in that it is subjected to cold working at room temperature with a reduction ratio of 40 to 90%. 9. The method of thermomechanical processing of a three-component alloy titanium-zirconium-oxygen (Ti-Zr-O) according to any one of paragraphs. 1-6, characterized in that - the original product is a three-component alloy in a recrystallized state, and the fact that it is subjected to cold working at room temperature with a reduction ratio of 40 to 90%, the cold-worked alloy is subjected to a heat treatment consisting in heating the alloy at a temperature of 500 to 650° C. for a period of 1 to 10 minutes. 10. Method according to claim 8 or 9, characterized in that the cold working consists of cold rolling. 11. The use of an alloy of titanium-zirconium-oxygen (Ti-Zr-O) according to any one of paragraphs. 1-7 as a material for the production of medical products. 12. The use of an alloy according to claim 11, where the medical product is a dental implant. 13. The use of an alloy of titanium-zirconium-oxygen (Ti-Zr-O) according to any one of paragraphs. 1-7 as a material for the production of products for the transport industry. 14. The use of an alloy of titanium-zirconium-oxygen (Ti-Zr-O) according to any one of paragraphs. 1-7 as a material for the production of products for the energy industry.

Images