WO2023021418A1 - Very high strength copper-titanium alloy with improved formability in the solution annealed temper - Google Patents
Very high strength copper-titanium alloy with improved formability in the solution annealed temper Download PDFInfo
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- WO2023021418A1 WO2023021418A1 PCT/IB2022/057654 IB2022057654W WO2023021418A1 WO 2023021418 A1 WO2023021418 A1 WO 2023021418A1 IB 2022057654 W IB2022057654 W IB 2022057654W WO 2023021418 A1 WO2023021418 A1 WO 2023021418A1
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- IUYOGGFTLHZHEG-UHFFFAOYSA-N copper titanium Chemical compound [Ti].[Cu] IUYOGGFTLHZHEG-UHFFFAOYSA-N 0.000 title claims abstract description 28
- 229910001069 Ti alloy Inorganic materials 0.000 title claims abstract description 26
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims abstract description 65
- 239000010936 titanium Substances 0.000 claims abstract description 52
- 229910052719 titanium Inorganic materials 0.000 claims abstract description 30
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 claims abstract description 26
- 229910052742 iron Inorganic materials 0.000 claims abstract description 25
- 239000010949 copper Substances 0.000 claims abstract description 15
- 229910052802 copper Inorganic materials 0.000 claims abstract description 11
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 claims abstract description 9
- 229910052782 aluminium Inorganic materials 0.000 claims description 9
- 229910052709 silver Inorganic materials 0.000 claims description 9
- 238000010791 quenching Methods 0.000 claims description 8
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 claims description 7
- 238000000137 annealing Methods 0.000 claims description 7
- 239000004332 silver Substances 0.000 claims description 7
- 239000012535 impurity Substances 0.000 claims description 6
- 238000010438 heat treatment Methods 0.000 claims description 5
- 238000004519 manufacturing process Methods 0.000 claims description 5
- 238000000034 method Methods 0.000 claims description 4
- 230000032683 aging Effects 0.000 abstract description 14
- 238000011282 treatment Methods 0.000 abstract description 3
- 229910045601 alloy Inorganic materials 0.000 description 111
- 239000000956 alloy Substances 0.000 description 111
- 229910017945 Cu—Ti Inorganic materials 0.000 description 17
- 238000003483 aging Methods 0.000 description 17
- 238000007792 addition Methods 0.000 description 12
- 230000000694 effects Effects 0.000 description 10
- 238000001330 spinodal decomposition reaction Methods 0.000 description 9
- 238000001556 precipitation Methods 0.000 description 8
- 239000000243 solution Substances 0.000 description 8
- 239000012071 phase Substances 0.000 description 7
- 230000035882 stress Effects 0.000 description 7
- 229910052804 chromium Inorganic materials 0.000 description 6
- 239000011651 chromium Substances 0.000 description 6
- PXHVJJICTQNCMI-UHFFFAOYSA-N nickel Substances [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 6
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 6
- 238000002441 X-ray diffraction Methods 0.000 description 5
- 230000015572 biosynthetic process Effects 0.000 description 5
- 239000000463 material Substances 0.000 description 5
- 239000002244 precipitate Substances 0.000 description 5
- 239000006104 solid solution Substances 0.000 description 5
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 4
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 description 4
- 229910000881 Cu alloy Inorganic materials 0.000 description 4
- 229910052759 nickel Inorganic materials 0.000 description 4
- 239000000126 substance Substances 0.000 description 4
- 229910052726 zirconium Inorganic materials 0.000 description 4
- 229910011212 Ti—Fe Inorganic materials 0.000 description 3
- 230000008901 benefit Effects 0.000 description 3
- 229910052796 boron Inorganic materials 0.000 description 3
- 239000013078 crystal Substances 0.000 description 3
- 229910000765 intermetallic Inorganic materials 0.000 description 3
- 229910052748 manganese Inorganic materials 0.000 description 3
- 239000011572 manganese Substances 0.000 description 3
- 230000007246 mechanism Effects 0.000 description 3
- 238000004626 scanning electron microscopy Methods 0.000 description 3
- 229910052710 silicon Inorganic materials 0.000 description 3
- 238000004627 transmission electron microscopy Methods 0.000 description 3
- ZOXJGFHDIHLPTG-UHFFFAOYSA-N Boron Chemical compound [B] ZOXJGFHDIHLPTG-UHFFFAOYSA-N 0.000 description 2
- PWHULOQIROXLJO-UHFFFAOYSA-N Manganese Chemical compound [Mn] PWHULOQIROXLJO-UHFFFAOYSA-N 0.000 description 2
- ZOKXTWBITQBERF-UHFFFAOYSA-N Molybdenum Chemical compound [Mo] ZOKXTWBITQBERF-UHFFFAOYSA-N 0.000 description 2
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 2
- QCWXUUIWCKQGHC-UHFFFAOYSA-N Zirconium Chemical compound [Zr] QCWXUUIWCKQGHC-UHFFFAOYSA-N 0.000 description 2
- 229910052786 argon Inorganic materials 0.000 description 2
- 239000010941 cobalt Substances 0.000 description 2
- 229910017052 cobalt Inorganic materials 0.000 description 2
- GUTLYIVDDKVIGB-UHFFFAOYSA-N cobalt atom Chemical compound [Co] GUTLYIVDDKVIGB-UHFFFAOYSA-N 0.000 description 2
- 238000001816 cooling Methods 0.000 description 2
- 230000003247 decreasing effect Effects 0.000 description 2
- 230000001627 detrimental effect Effects 0.000 description 2
- 239000007789 gas Substances 0.000 description 2
- 238000000265 homogenisation Methods 0.000 description 2
- 230000006698 induction Effects 0.000 description 2
- 238000002354 inductively-coupled plasma atomic emission spectroscopy Methods 0.000 description 2
- 229910052751 metal Inorganic materials 0.000 description 2
- 239000002184 metal Substances 0.000 description 2
- 238000001000 micrograph Methods 0.000 description 2
- 229910052750 molybdenum Inorganic materials 0.000 description 2
- 239000011733 molybdenum Substances 0.000 description 2
- 229910052698 phosphorus Inorganic materials 0.000 description 2
- 230000008569 process Effects 0.000 description 2
- 239000010703 silicon Substances 0.000 description 2
- 238000007711 solidification Methods 0.000 description 2
- 230000008023 solidification Effects 0.000 description 2
- 229910000906 Bronze Inorganic materials 0.000 description 1
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 1
- 229910010340 TiFe Inorganic materials 0.000 description 1
- 230000009471 action Effects 0.000 description 1
- 238000005275 alloying Methods 0.000 description 1
- 229910052787 antimony Inorganic materials 0.000 description 1
- 229910052785 arsenic Inorganic materials 0.000 description 1
- 229910052790 beryllium Inorganic materials 0.000 description 1
- 238000005266 casting Methods 0.000 description 1
- 210000004027 cell Anatomy 0.000 description 1
- 230000000052 comparative effect Effects 0.000 description 1
- RKTYLMNFRDHKIL-UHFFFAOYSA-N copper;5,10,15,20-tetraphenylporphyrin-22,24-diide Chemical compound [Cu+2].C1=CC(C(=C2C=CC([N-]2)=C(C=2C=CC=CC=2)C=2C=CC(N=2)=C(C=2C=CC=CC=2)C2=CC=C3[N-]2)C=2C=CC=CC=2)=NC1=C3C1=CC=CC=C1 RKTYLMNFRDHKIL-UHFFFAOYSA-N 0.000 description 1
- 210000001787 dendrite Anatomy 0.000 description 1
- 230000006866 deterioration Effects 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 230000018109 developmental process Effects 0.000 description 1
- 230000009977 dual effect Effects 0.000 description 1
- 238000001125 extrusion Methods 0.000 description 1
- 230000004907 flux Effects 0.000 description 1
- 229910002804 graphite Inorganic materials 0.000 description 1
- 239000010439 graphite Substances 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 229910052745 lead Inorganic materials 0.000 description 1
- 239000007791 liquid phase Substances 0.000 description 1
- 229910052749 magnesium Inorganic materials 0.000 description 1
- 239000000155 melt Substances 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 230000007935 neutral effect Effects 0.000 description 1
- 230000003647 oxidation Effects 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
- 238000005498 polishing Methods 0.000 description 1
- 230000008092 positive effect Effects 0.000 description 1
- 239000000047 product Substances 0.000 description 1
- 229910052761 rare earth metal Inorganic materials 0.000 description 1
- 150000002910 rare earth metals Chemical class 0.000 description 1
- 238000001953 recrystallisation Methods 0.000 description 1
- 238000001878 scanning electron micrograph Methods 0.000 description 1
- 238000005204 segregation Methods 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 239000007790 solid phase Substances 0.000 description 1
- 238000001228 spectrum Methods 0.000 description 1
- 230000000930 thermomechanical effect Effects 0.000 description 1
- 229910052718 tin Inorganic materials 0.000 description 1
- 231100000331 toxic Toxicity 0.000 description 1
- 230000002588 toxic effect Effects 0.000 description 1
- 229910052720 vanadium Inorganic materials 0.000 description 1
- 229910052725 zinc Inorganic materials 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C9/00—Alloys based on copper
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22F—CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS
- C22F1/00—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working
- C22F1/08—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of copper or alloys based thereon
Definitions
- the present invention relates to a copper alloy that can be used as a substitute for copper-beryllium (Cu-Be) alloys.
- the Cu-Be alloys are widely used in many applications where they are particularly appreciated for the combination of their high electrical conductivity and very good mechanical properties. They combine a temper (solution-annealed (SA) temper) with a very high ductility allowing extreme formability (elongation superior to 40%) and another temper (age-hardened (AH) temper) with an extremely high mechanical resistance (over 1 GPa). Nevertheless, they are doomed to disappear as Be is highly toxic and the alloys using this element are progressively forbidden.
- SA solution-annealed
- AH age-hardened
- Copper-titanium (Cu-Ti) alloys represent good alternative alloys to Cu-Be. Like Cu-Be alloys, the Cu-Ti alloys are age-hardenable alloys, i.e. , it is possible, under some specific conditions, to dissolve the alloying element Ti in the solid copper phase which has a face-centered cubic lattice. At this temper, often referred to as the solution-annealed temper (SA), the material provides usually the maximum formability.
- SA solution-annealed temper
- the Ti When the Cu-Ti alloys are aged at an intermediate temperature, usually between 300°C and 550°C, the Ti precipitates into a finely and uniformly dispersed a-Cu4Ti tetragonal nano-metastable phase (from 20 to 200 nm large), which considerably increases the strength of the alloy. If the alloy is maintained longer in temperature, larger orthogonal stable phases, referred to as [3-Cu4Ti or CusTi in the literature, form as cells on the grain boundaries and are detrimental for the mechanical properties of the alloy. This phenomenon is called “over-ageing”.
- US patent application No. 2004/0136861 discloses a copper alloy for use in connector materials and intended to have excellent bendability and to be preserved from the precipitation of CusTi.
- This copper alloy contains from 2 to 4 wt.% of Ti and from 0.01 to 0.5 wt.% of at least one element selected from Fe, Co, Ni, Cr, V, Zr, B and P as a third element group, wherein not less than 50% of the total content of the third element group exists as a second-phase particle.
- the present invention focuses on all the applications of Cu-Be that do not require good electrical conductivity but only high mechanical resistance. This allows adding a larger amount of Ti, usually detrimental to electrical conductivity. It is known that when Ti is added in the alloy in high amount (over 4% by weight), the Cu-Ti alloys exhibit a yield strength comparable with Cu-Be but suffer from a low ductility in the solution-annealed temper due to the difficulty of keeping the Ti in solid solution during the water quench which ends the solution annealing. For example, in a study on the effect of increasing the amount of Ti, S. Nagarjuna et al.
- US patent No. 4,599,119 discloses an age-hardened copper-titanium alloy containing from 2 to 6%, preferably from 3 to 5%, by weight of titanium and having an average crystal grain size not greater than 25 microns, preferably between 3 and 15 microns.
- this alloy may contain at least one element among iron, zirconium, chromium, boron and silicon, not exceeding 2% by weight in a total amount.
- the small crystal grain size is considered to improve mechanical properties of Cu-Ti such as isotropy, formability, fatigue strength, elongation and yield strength.
- the small crystal grain size is achieved through appropriate heat treatments, including a pre-annealing at intermediate temperatures to form spherical precipitates mentioned as a secondary phase.
- No particular effect is mentioned with regard to the possible use of iron, zirconium, chromium, boron or silicon.
- This patent does not address the problem caused by high amounts of titanium (over 4%) to the ductility of the alloy.
- US patent No. 2,783,143 discloses an age-hardenable copper-base alloy having improved strength and ductility in the age-hardened temper.
- This alloy contains from 1 to 10% titanium, from 0.1 to 1.6% cobalt, from 0.05 to 0.8% chromium, from 0.04 to 0.62% nickel, from 0.04 to 0.60% iron, from 0.02 to 0.28% molybdenum and from 0.005 to 0.08% manganese.
- this alloy contains from 2 to 6% titanium, from 0.2 to 0.8% cobalt, from 0.1 to 0.4% chromium, from 0.08 to 0.31 % nickel, from 0.075 to 0.3% iron, from 0.035 to 0.14% molybdenum and from 0.01 to 0.04% manganese.
- the indicated percentages seem to be atomic percentages.
- the content of titanium is 4%, which corresponds to about 3 wt.%.
- This patent focuses on the ductility in the age-hardened temper and does not mention the ductility before the age hardening, i.e., in the solution-annealed temper aiming at providing the maximum formability. Moreover, this patent does not address the problem caused by high amounts of titanium (over 4 wt.%) to the ductility of the alloy.
- WO 2021/143257 discloses a titanium bronze alloy for explosion-proof tools.
- the alloy comprises, by weight, from 5 to 7% titanium, from 0.8 to 1.5% aluminum, from 0.1 to 0.3% silver, from 0.2 to 0.4% iron, from 0.03 to 0.08% rare earth, the balance being copper.
- This document does not mention the ductility in the solution-annealed temper.
- the alloy proposed is expensive due to the presence of silver.
- Japanese patent application No. JP 2021/050393 discloses a titanium copper alloy plate for a vapor chamber.
- the alloy comprises, by weight, 4.8% of titanium and 0.2% of iron.
- a comparative example is mentioned which comprises, by weight, 5.2% of titanium and 0.2% of iron.
- the alloy in this document does not have an optimum ductility in the solution-annealed temper.
- An object of the present invention is to provide a copper-titanium alloy which can have both an excellent ductility in the solution-annealed temper and a high yield strength after an ageing treatment.
- a copper-titanium alloy comprising, by weight, at least 90% copper, from 5 to 7% titanium and from 0.25 to 0.5% iron.
- the content of titanium, by weight, is preferably at least 5.2%, preferably at least 5.5%, preferably at least 6%, and is preferably at most 6.5%.
- the content of iron, by weight, is preferably at most 0.4% and preferably at most 0.35%.
- the copper-titanium alloy may further comprise aluminum at a content of not more than 1.4% by weight, preferably at a content of from 0.1 to 1.4% by weight, preferably at a content of from 0.1 to 0.7% by weight, preferably at a content of from 0.1 to 0.6% by weight.
- the copper-titanium alloy comprises no or little silver, i.e. , the content of silver in the alloy is at most 0.08%, preferably at most 0.07%, preferably at most 0.06% by weight.
- the present invention further provides a method for manufacturing the copper-titanium alloy as defined above, with improved formability, comprising a solution annealing step comprising a heat treatment performed at a temperature of at least 840°C followed by a quench (fast cooling).
- FIG. 1 is a graph showing the elongation before ageing (at the solution- annealed (SA) temper) as a function of the yield stress (0.2% offset) after ageing (age-hardened temper).
- SA solution- annealed
- the data of Cu-XTi-0.3Fe alloys (with the nominal value X being equal to 3, 5 or 6) are superimposed with the commercial data of industrial CuBe-C17200 alloy and C72900 alloy at different tempers;
- - Figure 2 is a graph showing the evolution of the hardness in Vickers of the alloys Cu-6Ti and Cu-6Ti-0.3Fe over an ageing at 450°C from the solution-annealed temper
- - Figure 3 is a graph showing the stress-strain engineering tensile curves of the alloys Cu-6Ti and Cu-6Ti-0.3Fe at the solution-annealed (SA) temper and at a predetermined peak-aged condition (2h at 450°C) aiming at providing the maximum strength maintaining reasonable ductility in the age-hardened (AH) temper;
- FIG. 4 is a graph showing the evolution of the yield stress with the Ti content in the alloy, at the solution-annealed (SA) temper and at the age- hardened (AH) temper (2h at 450°C);
- FIG. 5 is a graph showing the evolution of the elongation at failure with the Ti content in the alloy, at the solution-annealed (SA) temper and at the age-hardened (AH) temper (2h at 450°C);
- FIG. 6(a) is a scanning electron microscopy (SEM) micrograph of Cu- 6Ti at the solution-annealed (SA) temper after chemical electro-polishing where the precipitates have consequently been exposed and are visible with a secondary electron detector. The hardness was measured at 320 Hv;
- FIG. 6(b) is a scanning electron microscopy (SEM) micrograph of Cu- 6Ti-0.3Fe at the solution-annealed (SA) temper after chemical electropolishing where the precipitates have consequently been exposed and are visible with a secondary electron detector. The hardness was measured at 160 Hv;
- TEM transmission electron microscopy
- - Figure 8 shows an X-ray diffraction (XRD) of Cu-6Ti (top curve, T6) and Cu-6Ti-0.3Fe (bottom curve, T7) in the solution-annealed temper.
- the top right windows I, II, III are three relevant zooms in the spectrum;
- - Figure 9 shows an X-ray diffraction (XRD) of three different alloys (Cu- 6Ti-0.1 Fe; Cu-6Ti-0.3Fe; Cu-6Ti-0.7Fe) in the solution-annealed temper, zoomed in the angle 20 corresponding to the diffraction of the plane ⁇ 100> of Cu;
- FIG. 10 is a scanning electron micrograph (SEM) of the alloys Cu-6Ti- 0.3Fe and Cu-6Ti-0.7Fe at the solution-annealed temper;
- FIG. 11 shows the hardness of three alloys (Cu-6Ti-0.3Fe; Cu-6Ti- 0.3Fe-0.2Ag; Cu-6Ti-0.3Fe-1 .2AI) at the solution-annealed temper and at the age-hardened temper.
- Copper-titanium alloys have been studied in the last century. They are conventionally manufactured by implementing the following sequence: a) Casting: the elements of the alloy are mixed at a high temperature in the liquid phase. An induction furnace is preferably used. The temperature is held for at least 1 min over the liquidus temperature (which is around 1000°C), preferably between 1200°C and 1300°C. The alloy is preferably cast in a mold to guarantee a faster cooling and better homogeneity of the melt. Depending on the Cu-Ti alloy, strategies can be used to introduce the elements in a specific order and/or from master alloys. b) Homogenization: a homogenization heat treatment is necessary to homogenize the Ti that segregates during the solidification process along the dendrites.
- a hot deformation in between 750°C and 900°C and/or a cold deformation can be performed to reach the final shape of the piece for a given application. Hot deformations increase the homogeneity of the microstructure with smaller grains and allow large deformations, while cold deformations give a better control of the geometry.
- SA Solution annealing
- AH temper Ageing or “age hardening”: the ageing is usually performed at a temperature comprised between 300°C and 550°C depending on the precold work, to precipitate the titanium and provide the maximum yield stress.
- the temper of the alloy after the ageing is called “age-hardened temper” or “AH temper”.
- the alloy At the end of the solution annealing, the alloy is soft and can thus be easily deformed to take its final shape.
- the alloy At the end of the ageing step, the alloy has a higher yield strength, but the latter depends on the content of Ti. It has been shown that increasing the content of Ti up to 7 wt.% increases the strength of the alloy in the age-hardened temper. However, it was then observed that with more than 4 wt.% Ti in the alloy, it is impossible to keep the Ti in solid solution after the water quench. This results in a wave-like microstructure observed in TEM (transmission electron microscopy). The mechanism behind this observation is controversial but always relates to an early-stage precipitation, resulting in a large increase in strength and a decrease in the ductility. This behavior is problematic, as it makes it impossible to produce a binary Cu-Ti alloy with high strength at the age-hardened temper (more than 850 MPa) and with high formability (elongation superior to 30%) at the solution- annealed temper.
- the present invention is based on the observation that small additions of Fe (0.25 to 0.5 wt.%, preferably 0.25 to 0.4 wt.%, preferably 0.25 to 0.35 wt.%) combined with a high content of Ti (5 to 7 wt.%, preferably 5.2 to 7 wt.%, preferably 5.5 to 7 wt.%, preferably 5.5 to 6.5 wt.%) results in suppressing this early-stage precipitation and keeping the titanium in solid solution.
- This allows doubling the elongation of the alloy in the solution-annealed temper, reaching then more than 40% and even more than 50% plastic deformation (elongation), while keeping, or even increasing, the yield strength of the alloy in the age-hardened temper (more than 900-1000 MPa).
- the grain size is preferred to be inferior to 30 pm.
- the content of Cu in the alloy of the invention is at least 90 wt.%. Excellent results are obtained when only Cu, Ti and Fe (and unavoidable impurities) are present in the alloy. Addition of one or more other elements such as Co, Zr, Si, P, Ni, Sn, Zn, Pb, Mn, Mg, As, Sb and Cr is not excluded in the invention but no improvement in terms of ductility in the solution-annealed temper and yield strength in the age-hardened temper has been observed with such added elements. A deterioration of the results with respect to Cu-Ti-Fe may even occur if the added element, e.g. Co, reacts with Fe.
- the added element e.g. Co
- the technical effect in the invention indeed relies on the action of Fe combined with a high content (5-7 wt.%) of Ti. Specifically in this high range of Ti, small additions of Fe increase considerably the ductility of the alloy. Unlike the aforementioned other elements, Fe has a special effect on Ti precipitation and ductility. Its role is expected to be in solid solution or through the formation of new nano-precipitates but not through the formation of secondary phases as described in US 2004/0136861.
- the solution heat treatment of the solution annealing is performed at a temperature of at least 840°C, preferably of at least 850°C, preferably of at least 880°C.
- the Cu-Ti-Fe alloys on which these results are based were manufactured as follows. Different model alloys T1 , T2, T3, T4, T6 and T7 were casted from high purity copper metal, iron and titanium sponges. About 500g of metal were weighted and melted in a sealed induction furnace under argon gas. After holding the temperature during 5 min at 1250 °C the alloys were poured in a graphite crucible to form 150 x 50 x 11 mm ingots. The resulting chemical compositions were analyzed in the middle of each ingot by Inductively Coupled Plasma - Atomic Emission Spectrometry (ICP-AES) and are shown in the table below, in weight percentages:
- ICP-AES Inductively Coupled Plasma - Atomic Emission Spectrometry
- the indications “ ⁇ 0.01 ” mean that the presence of the corresponding element in the alloy is not measurable.
- the Si in the alloys T1 to T7 is an impurity.
- the P in the alloy T2 is an impurity.
- the thermomechanical treatments were adapted to the amount of Ti for each alloy.
- the ingots were homogenized to get rid of the solidification chemical segregations, and then were hot rolled (HR) at 850°C under air, reducing the plates from 11 mm to 3.6 mm thick in three successive passes, in order to ensure a good dynamic recrystallization and small equiaxed grains.
- the alloys were successively cold rolled (CR), solution annealed with a flux of argon and water quenched (SA).
- the SA temperature and CR were tailored to reach a grain size under 60 pm. A grain size under 30 pm is preferred to reach better and more isotropic mechanical properties. These samples are referred to as the SA tempers in the following. Some of the specimens were then aged at 450°C, under Ar gas during 2h to produce the temper referred to as AH (age-hardened) temper.
- Figure 1 shows a graph aiming at demonstrating the main benefits of the Cu- 6Ti-0.3Fe alloy (alloy T7) in comparison with the Cu-Be (C17200), the binary Cu-Ti (alloys without iron T1 , T3 and T6) and a standard alternative alloy to Cu-Be (C72900). Thanks to the micro-addition of Fe, Cu-Ti(-Fe) alloys combine good formability before ageing and very high yield strength after ageing.
- Figure 1 shows the elongation before ageing (after quench; solution-annealed temper) on the y-axis, a value related to the formability of the alloys at this temper, and the x-axis gives the yield stress of the alloys after ageing, a value related to its resistance in working condition.
- This graph is relevant for any application, such as the Bourdon tubes in manometers, which requires a very high formability to manufacture products with complex shapes and high mechanical properties in the working conditions.
- the Cu-Be alloy (represented by squares in the graph) is by far the best in this dual behavior.
- Figure 2 shows the evolution of the hardness of the Cu-6Ti (alloy T6) and the Cu-6Ti-0.3Fe (alloy T7) as a function of the ageing time at 450°C. It can be observed that the addition of 0.3 wt.% of Fe into a Cu-6Ti alloy first increases the maximum hardness from 330 Hv to 350 Hv but especially stabilizes this hardness at 450°C. This shows that the micro-addition of Fe limits the over-ageing, which is one of the main challenges in Cu-Ti alloys, always associated in the literature with the formation of the stable phase [3-Cu4Ti (or CusTi) at the grain boundaries.
- Figure 3 shows that Cu-6Ti-0.3Fe (alloy T7) is softer than Cu-6Ti (alloy T6) at the solution-annealed (SA) temper and harder than Cu-6Ti at the age-hardened (AH) temper.
- SA solution-annealed
- AH age-hardened
- the Cu-6Ti-0.3Fe also exhibits a very profitable balance between yield strength and elongation at the age-hardened temper. This balance between strength and formability is superior to the one in the commercial Cu-Be alloys and the standard commercial Cu-15Ni-8Sn alternative. Unlike comparable commercial alloys on the market, the Cu-6Ti-0.3Fe in the age-hardened state can reach a yield stress superior to 1 GPa with an elongation superior to 15%.
- Figures 4 and 5 respectively show the evolution of the yield stress and of the elongation at failure as a function of the Ti content in the alloy, at the solution- annealed temper and the age-hardened temper, for the alloys Cu-Ti and Cu-Ti-Fe (0.3 wt.% Fe) processed as described above and for the binary Cu-Ti alloys with a grain size of 60 pm disclosed in the article “On the variation of mechanical properties with solute content in Cu-Ti alloys” by S. Nagarjuna et al., Materials Science and Engineering A259 (1999) 34-42, and processed as described in the said article. These figures illustrate the need of having a high Ti content (5-7 wt.%) to observe significantly the described benefits of Fe micro-additions.
- FIGs 6 and 7 The physical mechanism in which micro-additions of Fe are effective is illustrated in Figures 6 and 7.
- the nano-precipitation in the alloy Cu-6Ti (alloy T6) is visible in Figure 6(a) and, by the very specific wave-like aspect along the direction ⁇ 200>, in Figure 7(a). It can be seen from Figures 6(b) and 7(b) that the microadditions of Fe in the alloy completely suppress such early precipitation.
- Figure 8 shows an X-ray diffraction (XRD) of Cu-6Ti (top curve, alloy T6) and Cu-6Ti-0.3Fe (bottom curve, alloy T7) in the solution-annealed temper. It confirms the assumptions of the mechanism explained above.
- XRD X-ray diffraction
- Figure 9 shows X-ray diffraction (XRD) results for three different alloys (Cu-6Ti-0.1 Fe; Cu-6Ti-0.3Fe (alloy T7); Cu-6Ti-0.7Fe) at the solution- annealed temper.
- XRD X-ray diffraction
- the content of Fe must however not be too high since otherwise large undesired TiFe intermetallics are formed which have a negative impact on the ductility and mechanical properties of the alloy. Such large intermetallics are visible in Figure 10 for Cu-6Ti-0.7Fe.
- Figure 11 shows the hardness of the Cu- 6Ti-0.3Fe in the solution-annealed temper and in the age-hardened temper without Ag nor Al in the alloy (left-hand graph), with 0.2 wt.% Ag in the alloy (middle graph) and with 1.2 wt.% Al in the alloy (right-hand graph).
- Al softens the alloy in the solution-annealed temper, thus improving the ductility in that temper, without decreasing the hardness in the age-hardened temper.
- the content of Al must however be sufficiently low to avoid the formation of intermetallics with Fe.
- the alloy according to the invention preferably includes no or little Ag, i.e. , the content of silver in the alloy is at most 0.08 wt.%, preferably at most 0.07 wt.%, preferably at most 0.06 wt.%.
- An alloy comprising only Cu, Ti, Fe and Al (and unavoidable impurities) can therefore be particularly advantageous.
- the alloy according to the invention can replace the Cu-Be alloys in any very high strength alloy application requiring good mechanical properties and where a good electrical conductivity is not needed, for example the Bourdon tubes in high- pressure manometers, parts of timepieces (e.g., watch cases, gears, escapements, balances, springs, shafts, oscillating weights, plates, bridges, hands, dials, discs, etc.), ball-roller bearings and bushings, in particular for the aircraft and airspace industry, and dies for plastic extrusion.
- timepieces e.g., watch cases, gears, escapements, balances, springs, shafts, oscillating weights, plates, bridges, hands, dials, discs, etc.
- ball-roller bearings and bushings in particular for the aircraft and airspace industry, and dies for plastic extrusion.
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Citations (5)
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US2783143A (en) | 1954-06-24 | 1957-02-26 | Driver Co Wilbur B | Age-hardenable, copper-base alloy |
US4599119A (en) | 1983-11-22 | 1986-07-08 | Ngk Insulators, Ltd. | Age-hardening copper titanium alloy |
US20040136861A1 (en) | 2002-11-29 | 2004-07-15 | Nikko Metal Manufacturing Co., Ltd. | Copper alloy and producing method therefor |
JP2021050393A (en) | 2019-09-25 | 2021-04-01 | Jx金属株式会社 | Titanium copper alloy sheet for vapor chamber and vapor chamber |
WO2021143257A1 (en) | 2020-01-17 | 2021-07-22 | 河北中泊防爆工具集团股份有限公司 | Titanium bronze alloy material, preparation method therefor and application thereof |
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- 2022-08-16 WO PCT/IB2022/057654 patent/WO2023021418A1/en active Application Filing
Patent Citations (5)
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US2783143A (en) | 1954-06-24 | 1957-02-26 | Driver Co Wilbur B | Age-hardenable, copper-base alloy |
US4599119A (en) | 1983-11-22 | 1986-07-08 | Ngk Insulators, Ltd. | Age-hardening copper titanium alloy |
US20040136861A1 (en) | 2002-11-29 | 2004-07-15 | Nikko Metal Manufacturing Co., Ltd. | Copper alloy and producing method therefor |
JP2021050393A (en) | 2019-09-25 | 2021-04-01 | Jx金属株式会社 | Titanium copper alloy sheet for vapor chamber and vapor chamber |
WO2021143257A1 (en) | 2020-01-17 | 2021-07-22 | 河北中泊防爆工具集团股份有限公司 | Titanium bronze alloy material, preparation method therefor and application thereof |
Non-Patent Citations (2)
Title |
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ROUXEL B ET AL: "Micro-addition of Fe in highly alloyed Cu-Ti alloys to improve both formability and strength", MATERIALS & DESIGN, ELSEVIER, AMSTERDAM, NL, vol. 213, 25 December 2021 (2021-12-25), XP086935490, ISSN: 0264-1275, [retrieved on 20211225], DOI: 10.1016/J.MATDES.2021.110340 * |
S. NAGARJUNA ET AL.: "On the variation of mechanical properties with solute content in Cu-Ti alloys", MATERIALS SCIENCE AND ENGINEERING, vol. A259, 1999, pages 34 - 42 |
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