JPH05504996A - Spray casting aluminum/lithium alloy - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] Spray casting aluminum/lithium alloy The present invention has a low content of both sodium and hydrogen and is produced by spray precipitation. between aluminum and lithium alloys.

Aluminum-lithium-based alloys are used in applications that require low weight and high stiffness, especially in aviation. It is of great interest for space applications. However, Al-Li alloy has a hybrid cutting direction. found to have relatively low ductility, fracture toughness and stress corrosion crack growth resistance. has been done.

Kojima and others sing! As-cast and hot cast aluminum lithium 8090 alloy The mechanical properties of both after compression are tested (for A-I-L i alloys). 5th w’s, AIME, p85.1989>, they reported the letter D in the literature. Mechanical properties of Uta-g cast alloy compared to values for Cfs-cast 8090 alloy reported an apparent improvement, but no direct comparison was made; Mechanical properties are due to the finer grain structure found in spray cast alloys It is something.

Fager et al. reported interfold cracking in AI-Li alloy. (Scripta Metallurgica Vol. 20. pH 59゜1 986), sodium, along with potassium and titanium, has a potential embrittling side. It has been indirectly identified as

Miller et al. showed that i-open cracks are not limited to Al-Li alloys. Reported (Scripta Metalurgica Vol. 21゜p. 663.1987), AI/Lf gold alloy with sodium content of approximately 10 ppm or less If so, what is that alloy? ! No open cracks were observed. W open is crystal It was believed that this was due to sodium segregated to grain boundaries and grain matrix interfaces. .

Although the effect of hydrogen content on the mechanical properties of AI-Li alloys has not been quantified, Moreover, the aluminum alloy exhibits unexpectedly good cross-section mechanical properties after machining. Gold is produced by spray precipitation and the scales! I also found it outside. Therefore, - in a manner Therefore, the present invention is an aluminum casting process in which a molten aluminum alloy containing volatile impurities is subjected to sound-W casting. Provided is a method for reducing the volatile substance content of aluminum alloys.

The term “volatile substance J” as used herein refers to gaseous or high vapor pressure impurities, e.g. Includes hydrogen or alkali gold 17XM.

Preferably, the melt is jet cast to form a cohesive deposit. This method is , especially for the removal of Na and H2 impurities.

The present invention provides a method for reducing the sodium and/or hydrogen content of any aluminum alloy. It can also be applied to This method is used to determine the sodium content of aluminum alloys and other To be able to reduce the balance of alloy components without significantly changing their balance. Spray deposits are , which may be remelted or shaped to give a low sodium aluminum feedstock. The formed spray deposit can be used directly or further processed before use. Good too.

It is particularly applicable to the aluminum-lithium based alloy of the present invention. According to another embodiment of the invention, 2.5 ppm or less sodium and 1 ．． Spray-cast aluminum-lithium based composites containing 0 ppm or less hydrogen money is provided.

The aluminum-lithium based alloys of the present invention typically contain 0.5 to 7% lithium. 2 to 6% of lithium, preferably 2 to 6%. The starting material is an aluminum-lithium alloy cast in a conventional DC method, or The alloy may be made by another method, such as C casting alloy sodium The content is generally around 10 p, m, typically around 5 ppm, but 3 ppm It can be as low as . Preferably the sodium content of the starting alloy is 10 ppm Or maybe less.

The sodium content of the Al-Li alloy is preferably a content at which interfold defects are observed; Although it is recognized that typically it should be less than about top per million, the present invention In combination with the reduced hydrogen content, the sodium levels can be reduced by sodium segregation. This significantly reduces the level at which found that it exhibited unexpectedly improved properties. Ductility and tensile strength are Increased in both long-cross and cross-cut directions. Fracture toughness is also determined in the cross section direction Improved. Resistance to stress corrosion crack growth and ribbon crack growth is substantially increased. It will be done. The mechanical properties in some areas, e.g. in the longitudinal direction, may be slightly reduced. However, the alloys of the present invention exhibit improved properties overall.

The aluminum-lithium based alloy of the present invention has a Na content of 2.5 ppm or less. and preferably H2 of IPPm or less.

The hydrogen content of DC4i Al-Li alloys is typically between 0.5 and 0.8 ppm. within range, but can be as low as 3 pPm. High lithium alloy odor In alloys that typically have a lithium content of 4% or more, Although it is known that hydrogen content increases, the reason for this is not understood. .

For alloys with a Li content of 3% or less, the H2 content is preferably 0.3PPm or less, preferably about 0.3PPm or less. lppm or less, but For alloys with a lithium content greater than 3%, the H2 content may be up to lppm. However, it is preferably 8 ppm or less.

The alloy according to the invention can contain other elements (excluding Na and H2) if they are A1- A preferred alloy may contain 8 090.8091 series alloy 6 The present invention includes an alloy in a spray cast state, rolling, Manufactured by extrusion, forging, hot isostatic pressing or any other form of processing. Its scope includes both products and. Refined alloys can also be remelted as a source of low impurity materials. It may be melted or recast.

Many factors in the spray precipitation process affect the final sodium content of the sprayed ingot. and hydrogen content.

One factor that influences the final sodium and hydrogen content is the crucible in which the melt is made. The crucible should preferably not be gas permeable, the permeability of the crucible should be , allowing significant interaction between the outside atmosphere (air) and the melt, thus increasing This can result in high hydrogen levels. The preferred crucible material is resin-bonded carbon. Opaque or semi-permeable materials such as silicon carbide or bonded graphite crucibles include. Other crucible materials include alumina, fused silica, magnesia and silica. Includes syalon as well as refractory lined steel crucibles. a certain type Impure refractories such as alumina react with the melt to reduce sodium and hydrogen levels. may be increased. To reduce this problem, the crucible is made of a material such as boron nitride. treatment with a similar coating to suppress the reaction between the melt and the crucible and It may be treated with a coating such as Luconia to reduce permeability. other appropriate Coatings will be known to those skilled in the art.

The surface area to volume ratio of the entire melt reduces the degree of interaction with the atmosphere should be kept as low as possible (typically 0.015, preferably 0.038 or less). It is possible. The atmosphere is as dry as possible (typically <110 PP, preferably <6 ppm moisture) and hydrogen levels as low as possible (typically toppm, Preferably <ippm) should be maintained so that the water vapor is This is because it is believed to be the main cause at the elementary level. Preferably the atmosphere is Should be inert to reduce oxidation. Vacuum melting may not be necessary found.

Removal of volatile or gaseous impurities is performed using small particles (typically -80 μm, preferably 200 μm).

However, as particle size decreases, flight time decreases and thus removal occurs. There will be a short period of time for you to learn. These two factors are the lowest in the precipitate. Vary to optimize conditions to yield sodium and hydrogen levels of It can be done.

Reduced gaseous impurity levels if particles are not precipitated into dense boundaries would not be able to be retained in the solid state.

Degassing also occurs from the hot surfaces of the ingot during atomization. This solid or semi Solid-state degassing will be enhanced in precipitates with larger thermal mass; This is because heat is retained for a longer period of time.

In the following examples, the secondary gas pressure is 1.2-3 bar and the secondary gas pressure is 55-9 bar. bar, and the transfer gas pressure was 3-5 bar. -The next gas flow rate is 0.25. The speed was 0.45 m'/min. Secondary gas flow rate is 6.0 to 9.2m’77min Met. The metal flow rate was 5 to 14 kg/min. Melting temperature is 700″ The 0 condition, which was between 800°C and 800°C, was liquid or semi-liquid at the time of collision, and The above range so as to produce metal particles with a diameter smaller than 200 μm. Adjusted within. The above range may vary slightly from one machine to another. However, suitable ranges for producing such particles can be readily determined.

By adjusting within the above range, the particle size and flight time of the particles can be controlled by volatile impurities. thing! can be optimized to achieve maximum removal of material.

Implementation Tsuba 1 The spray casting equipment was designed and specified by Alcan International Limited. Mannesemann Demag, West Germany and Osprey Metals, Nea th) and Alcan International Limited It was further developed in the Banbury Laboratories Lease. Alloy to be sprayed The Morgan Salamander Excel rExc　e　I　　　　Crucible [Resin bonded SiC; 40% SiC and 30% Carbon] (The crucible was cleaned with a graphite/clay-based wash and then washed with boronitride. The material was melted by induction heating in the material coated with the material. This equipment uses overpressure Includes a refractory nozzle for passing the ejected metal stream. of that nozzle surrounding the molten surface and taking the metal flow parallel to and including the molten surface. A primary gas nozzle is installed having an aperture to direct the primary support gas flow in a circumferential manner. It's wrapped.

A secondary atomizing gas stream is directed around the secondary gas nozzle toward the molten metal stream. It is surrounded by a secondary gas nozzle with an orifice. The secondary gas flow is downstream of the nozzle. contacting the flow of molten gold at a certain distance from and spraying with it, the metal particles Let it be a child spray.

The secondary atomizing gas flow has a height and radius equal to the distance of the jet from the gold stream. It defines a conical shape.

The molten metal was sprayed onto a rotating aluminum alloy collector. The spray gas used The gas and transfer gas were nitrogen. Melt temperature is 710”C, melting and holding The total time was 3 hours and 50 minutes. The flow rate is 10.9 kg/min and the time is 8 minutes 11 seconds. The spray time produced a spray deposit weighing 76.3 kg.

The sprayed alloy is a monolithic 8090 aluminum rim from a DC casting starting material. It was a lithium-based alloy. Presses made from sprayed preforms The properties of the extrudates were compared to the properties of extrudates made from DC steel starting billets.

The preform was homogenized with a DC casting control at 550°C for 24 hours. It was. The sprayed preform and DC Senzo billet were machined into a 210 mm diameter and extrude 2.5 inches x 1 inch using the parameters below. A bar with a rectangular cross section was used.

Fillet/Temperature Exit speed J 11 top - color] - Reset J" 7 minutes Front Bel spray 435/440 0.76 405 390DC casting 435/4 40 0.84 415 385 The extrusion ratio is 201 for both ingots. It was. For evaluation, the front (front end side) and back (back end side) of each extrudate were measured. A portion of appropriate length was taken. The chemical analysis values for these extrudates are as follows: there were.

Li　Cu　Hg　Zr　Si　Fe　Ti　Ha　H2-----1---- -~-------(wH)--------------------------p H1l-DCfs construction 2,39 1,20 0,83 0,13 0,04 0 ．． 04 0.031 +2 1.20 injection Wi 2.30 1.10 0.80 0,13 0,03 0.04 0.049 (10,19 Then the extrudate flow The front end (!@) piece was treated at 540°C for 172 hours, quenched with cold water, Then, it was pulled 2%.

Tensile test pieces in the longitudinal direction, longitudinal transverse direction, and laminar cross-sectional direction, as well as 5T-L toughness test pieces. Then, it was aged and buried at 170°C for 48 hours. About spray processing and DC casting 8090 The tensile properties in all three orientations are given below.

IQ Boar 4 Spout Longitudinal direction -0,2! PS (MPa) 537 512TS (MPa>57 2 550 Elongation rate (%) 4.7 5.1 Long transverse direction -0,2Z PS (MPa) 409 390TS (MPa> 443 487 Elongation rate (%’) 0.7 8.5 Short transverse direction -0,2Z PS (MPa) 344 350TS (MPa> 356 485 Elongation rate (%) 0.4 8.4 The grain size taken from the longitudinal part of spray processing 8090 is 155 microfron× It is on the order of 25 microns, and DC casting 8090 is 300 microns x 1 ~ mm. The grain size of the isotropically processed material was 70 microns. The table below is , DCg construction and blow processing from 10mm thick compact tensile strength 5T-L test piece 8゜9 It gives a fracture toughness of 0.

1.D Condition K1c Pa　m DC casting 24/170℃ 1421 DC casting 48/170℃ 14.38 injection H24/170℃ 25.25 OJi! Fog 48/170℃ 17.18* Invalid test due to insufficient thickness : Therefore, the kg value is quoted.

The stress corrosion crack growth rate and ribbon crack growth rate are shown in Figures 1 and 2, respectively. Ru.

This improved combination! Mechanical properties of II mist casting compared to DC casting products This results entirely or primarily from the reduced Na and H2 content of the product.

Oshi 3yu In order to understand the effect of sodium and hydrogen content on the mechanical properties, various sodium An 8090 alloy preform with lithium and hydrogen content was made. Device was substantially the same as above. Crucible is semi-permeable alumina/silica fiber type, which was coated with zirconia and boron nitride. Melt temperature The temperature is 71f)°C.

Sodium content can be varied by changing the sodium content in the starting ingot It was done. The hydrogen content is varied by doping with atomizing gas and water vapor. Ta.

Another preform was made using the equipment described in Example 1. . The melt temperature was 710''C with a flow rate of 9.3 kg/min.

Preform and a! ! Machined into a 28mm thick rolling block. None, homogenization treatment was performed at 540°C for 24 hours. The sample was rolled to a thickness of 25 mm, and Reheat between each pass. Solution treatment at 530°C and 24 hours at 170’C It was aged and tested in the cross section direction. The chemical composition of the rolled plate was determined by cross-sectional elongation. The ratio and fracture toughness values are shown in the table below.

Li Ha H2 1=wtl−−−−−ppa+−−−−elongation rate? 6 Fracture toughness kg (MPa, sl /2) sample 1 2.31 5 0.57 0.62 19.62 2.34 22 0.3 3 1.00 17.83 2.5 + 13 0.44 0.87 17.44 2.31 6 0.41 1.82 23.05 2.24 1 0.28 6.14 27.2 Elongation and toughness according to the present invention compared to comparative samples 1 to 4 There is a significant increase in the produced sample 5.

Kyoenyu 8090 alloy preforms under fSiXI conditions substantially as described in the Examples. I wrote the song Ws. Alloys and spray-processed pre-formed products before Uta W The chemical composition of foam) is shown below.

Si Fe Cu Mg B Zr Ha Li Naragiri -pps- 10,060,051,370,9430,12602,65Z　O,060, 041,330,8730,121002,48 after spraying 1 0.06 0.05 1.24 0.88 3 0.12 13 2.51 2 0.07 0.04 1.32 0.83 3 0.12 22 2.34 All values are given in wt% except Na-ppm.

! Giving A Melting and holding time = 2 hours 50 minutes Flow rate: 8.85kg/min Implementation time: 22 minutes 42 seconds Narugiri molded product weight: 152.7kg An 85 mm thick block was cut horizontally across the spray molding and heated at 550'C for 2 Homogenized for 4 hours. Cut this to 130mm length x 90mm width x 85mm thickness. As a rolling block, the material is rolled at 540"C from 85mm to 28mm thick. It was rolled down in a bath 5 times.

Seiwei Starting material - 8091 alloy Mouth Standing Deaf Back Δ ■ Practice Death ■ 2.70 1.90 0,85 0 ．． 10 0.04 0.06 0.41 22 0.95 of the rolled plate Cut out the material from the center and prepare a blank for ST tensioning at 545°C. It was treated with S, H, and T for hours and quenched with oil. These were then heated at 170°C in an untensioned state. It was aged for 48 hours.

The tensile properties were as follows.

Example 5 Results showing water production reduction in 7000 series aluminum alloy.

The alloy was a non-standard product, but contained 5.0-70% zinc and 2.0-2.5% mag. Contains nesium. Three spray experiments were conducted.

Experiment 1 - The starting metal had 0.29% H2 and after spraying this was 0.09°5 descended to

The actual $2-82 level fell from 0.46% to 0.20%.

The actual $3-82 level fell from 0.32% to 0.17%.

In all cases spray conditions are for the aluminum-lithium alloy example. was substantially the same.

Crack growth rate (rr+/s) Crack length (mm) abstract Has low levels of impurities, especially hydrogen and sodium, and improved mechanical properties Aluminum lithium alloy showing quality.

international search report Shin^Hitomi r+llll9e--1^o-1-cl-', PCfu:/GIji91100 381 international search report GB 9100381 SA 45325

Claims (11)

[Claims] 1.2.5ppm or less sodium and 1.0ppm or less Spray-cast aluminum-lithium alloy containing hydrogen. 2. Spray cast aluminum according to claim 1, wherein the lithium content is from 0.5 to 7%. Mu-lithium alloy. 3. Spray cast aluminum according to claim 2, having a lithium content of 2 to 4%. Lithium alloy. 4. Any one of claims 1 to 3, wherein the hydrogen content is 0.3 ppm or less. One spray cast aluminum lithium alloy. 5. Any one of claims 1 to 4, wherein the alloy is an 8090 or 8091 series alloy. or one spray-cast aluminum-lithium alloy. 6. A method of spray casting aluminum alloys with low content of volatile impurities. The aluminum alloy containing volatile impurities has a diameter smaller than 200 μm. and ejected under conditions that produce particles that are liquid or semi-liquid upon impact. A method characterized by mist casting. 7. The primary gas pressure is 1.2 to 3 bar and the secondary gas pressure is 5.5 to 9 bar. 7. The method of claim 6, wherein the gas pressure is between 3 and 5 bar. 8. The primary gas flow rate is 0.25 to 0.45 m3/min, and the secondary gas flow rate is 6 m3/min. to 9.2 m3/min and the metal flow rate is 5 to 14 kg/min. Method for scope 6 of the request. 9. 9. The method of claim 8, wherein the volatile substance is hydrogen. 10. 9. A method according to claims 6 to 8, wherein the volatile substance is an alkali metal. 11. 11. The method of claim 10, wherein the alkali metal is sodium.