A kind of solid solution treatment method of heat-proof magnesium-base rare earth alloy
Technical field:
The present invention relates to a kind of solid solution treatment method of heat-proof magnesium-base rare earth alloy.Particularly relate to and contain the repeatedly thermal shocking formula solid solution treatment method that more than one rare earths are the higher heat resistance magnesium alloy of main alloy element and content of rare earth.
Background technology
The resistance toheat of magnesium-rare earth alloy is good, in automotive industry and high-tech sector important use is arranged.In order to improve the mechanical property of such alloy, generally to pass through T5 or T6 thermal treatment.Therefore, thermal treatment process has property of crucial importance for such alloy.For example, WE54, WE43 heat treatment of alloy technology are generally 8 hours water-cooleds of 525 ℃ of insulations, then at 16 hours air coolings of 250 ℃ of timeliness.In recent years, in the thermal treatment field, occur in succession such as technology such as " classification solid solution, secondary solid solution, reinforcement solid solution, dual timeliness, overaging and stage homogenizing ".These are forwarded in the thermal treatment process as structured material by many thermal treatment process as functional materials of past, and wherein secondary solid solution and dual timeliness are especially noticeable.Solid solution in the alloy heat treatment process and ageing treatment have critical role to improving alloy property.One of purpose of the solution treatment of alloy is that solutes such as the atom of strengthening element, intermetallic compound are dissolved in the alloy substrate as much as possible, makes the alloy homogenizing.And one of purpose of timeliness is that the solute that is dissolved in the alloy substrate is separated out gradually again, and from then on process sees that the two is reciprocal.
No. 200510129121.7, Chinese invention patent discloses the patent that is entitled as " improved method by solid-state connection processing aluminium alloy capability " that Boeing Co. applied in June, 2006.The treatment process that this invention has all adopted classification to optimize in to 7050 Aluminium Alloy Solution Treatment and artificial aging process.Be in particular in: it carried out anneal one time to alloy earlier in 371 ℃~427 ℃ temperature range before solution treatment, again alloy is carried out solution treatment then in 454 ℃~538 ℃ temperature range.Artificial aging then was divided into for two steps, and the first step be 121 ℃ of low temperature agings 4 hours, and second step was 177 ℃ of higher temperatures timeliness 8 hours.As seen the outstanding advantage of this invention is the distinguished anneal that solution treatment is increased before.This invention is interpreted as principle, purpose and the effect of this annealing treating process of increase: this thermal treatment, and be lower than under the sosoloid thermal treatment temp in temperature and carry out, discharge the storage energy in the aluminum alloy materials.Thereby make this material in the solution heat treatment process, not have enough energy that recrystallize and exaggerated grain growth take place.The essence of this processing is for selecting to be lower than common solid solution temperature, and be higher than common aging temperature, carry out once " intensification-insulation-cooling " process being in " solid solution-timeliness " medium temperature point, " intensification-insulation " wherein is for better release stores and can prepare, and temperature-fall period is for discharging the process of storage energy.
Ning Ailin etc. have adopted the quick solution heat treatment novel process of secondary to the 7A04 aluminium alloy, the result shows: all be controlled at total solution time under 8 minutes the prerequisite, single-stage solid solution condition is 470 ℃ or 485 ℃ and is incubated 8 minutes, secondary solid solution condition is: 470 ℃ of insulations then heated up 485 ℃ and are incubated 3 minutes again in 5 minutes, and total soaking time also is 8 minutes.The alloy at room temperature intensity Rm that the single-stage solid solution obtains is about 422.3MPa; The alloy at room temperature intensity that the secondary solid solution obtains be 477.4MPa (Ning Ailin, Ceng Sumin, 7A04 aluminium alloy quick thermal treatment process research [J]. light metal, 2004, (6): 51-54).The quick solid solution craft of secondary of " first low temperature, the back high temperature " of this research has obviously improved alloy strength.
No. 00113246.6, another Chinese patent discloses the patent that is entitled as " solid solution of aluminium, magnesium alloy or homogenization heat treatment method ", this patented invention the novel method of a kind of can being referred to as " reinforcement solution treatment " or " cross solution treatment ".Common solid solution temperature all is chosen in following 15 ℃ or lower of the polyphase eutectic point of alloy or peritectic point temperature, to avoid burning.Though and the starting temperature of this invention solution treatment is chosen in molten following 5 ℃~30 ℃ of polyphase eutectic point or peritectic point temperature T,, slowly heat up, until temperature being elevated to above polyphase eutectic point or more than the peritectic point temperature T fusing point 5 ℃~30 ℃.The advantage of this invention is to improve the solution treatment efficient of alloy.
On September 20th, 2006, Chinese patent disclosed the patent that is entitled as " a kind of two-stage forced solution treatment method that is applicable to the high-strength deformation aluminium alloy " for No. 200510127750.6, this patent with the trade mark be 7055,7B04, B96 be concrete object, method by the secondary solution treatment makes the intensity of Al-Zn-Mg-Cu system high-strength deforming aluminium alloy improve 3%~10%, and unit elongation improves 1%~5%.
For Magnuminium, though there is not patent to point out that relevant patent such as secondary time effect has open such as above-mentioned secondary or novel process such as classification solution treatment at aluminium alloy.The patent that is entitled as " high-strength magnesium alloy and preparation method thereof " that Chinese patent CN00819991.4 number, Canadian Patent CA2423459 number, European patent EP 1339888A0 number and World Intellectual Property Organization patent center disclose same core content WO0227053 number.One of advantage of these inventions is that the alloy that the Mg-6%Zn-3%Al-2.5%Si-1%Mn-0.4%Ca that is invented forms is used dual aging thermal treating process.This dual aging technique is first low temperature, back high temperature, as earlier about 90 ℃ to alloy timeliness first, then about 180 ℃ to the alloy secondary ageing.This dual timeliness is compared increases such as the alloy grain size reduces, hardness, intensity with simple timeliness once.In addition, another Chinese patent of the reversed in order of " the first low temperature; back high temperature " of patent is CN200510030457.8 number therewith, the patent that is entitled as " high-strength cast Mg alloy containing rare-earth and preparation method thereof " was disclosed in March, 2006, this invention to 200 ℃~250 ℃ of the advanced row of alloy high temperature again the two-stage time effect of 150 ℃~200 ℃ of low temperature handle.In fact, in research rareearth magnetic material process, just found that two-stage time effect can significantly improve the performance of rareearth magnetic material already before 15 years.To a concrete alloy is the order of selecting " first low temperature, back high temperature " on earth, still selects opposite order, not only will consider to separate out the particular case of the solute of particle, and will consider to separate out the solvent situation that particle will enter.As U.S. Pat 4,746, " be applicable to the Sm of permanent magnet material disclosed being entitled as in 1998 No. 378
2Co
17Production technique " patent.This invention is adopted dual timeliness heat treatment technics to its material, being chosen as of twice aging temp " first high temperature, back low temperature "; Aging temp is 830 ℃ first, can make to be solid-solubilized in Sm in (α) Co matrix
2Co
17Separate out.Aging temp is 410 ℃ for the second time, is for being solid-solubilized in Sm in (ε) Co matrix
2Co
17Separate out and design.One of associated advantages of this invention (α) Co among the alloy substrate Co that has been more careful consideration and (ε) otherness of Co.Dual timeliness in the foregoing invention can be used for reference, but ageing treatment is compared in processing intent, microscopic mechanism etc. with solution treatment and made a world of difference.
More than these innovative technologies whether be applicable to the heat-proof magnesium-base rare earth alloy solution treatment, do not see always patent disclosure and article the report.And the otherness of aluminium alloy in the above-mentioned quick solution heat treatment novel procesies of mentioning of Al-Zn-Mg-Cu line aluminium alloy secondary such as 7A04 and magnesium-rare earth alloy each side is quite big, and the atomic radius difference of the atomic radius of main strengthening element and matrix Al is little in the alloy.And the atomic radius difference of rare earth atom radius in the heat-proof magnesium-base rare earth alloy and matrix Mg is bigger; And precipitate mostly is RE: 1: 5 intermetallic compound of Mg ≈, obviously, this technology can not be applicable to the heat-proof magnesium-base rare earth alloy solid solution treatment process fully.In addition, for the higher heat-proof magnesium-base rare earth alloy of content of rare earth, the intermetallic compound of separating out surpasses polyphase eutectic point or whether feasible 5 ℃~30 ℃ the time more than the peritectic point temperature in temperature, does not then come to a conclusion.Therefore, exploitation is applicable to that heat-proof magnesium-base rare earth alloy solution treatment novel process is necessary.
Summary of the invention:
At the existing blank of heat-proof magnesium-base rare earth alloy solid solution treatment process, solve the difficult problem that existing solid solution treatment process can not finely be applicable to the heat resistance magnesium alloy solution treatment of high rare-earth content, the object of the present invention is to provide a kind of solid solution treatment method of heat-proof magnesium-base rare earth alloy, be specifically related to a kind of repeatedly thermal shocking formula solution treatment novel method that is applicable to the heat-proof magnesium-base rare earth alloy solution treatment.
The principle of thermal shocking formula of the present invention solution treatment is:
1 〉, the basic definition of thermal shocking formula solution treatment is: the holding stage in the solution treatment of routine increases once above " insulation-intensification of cooling-low temperature " and operate, and that solid solution is incubated total time is constant; The single job of being somebody's turn to do " insulation-intensification of cooling-low temperature " is defined as a thermal shocking.Twice operation is defined as the secondary thermal shocking, and the rest may be inferred.Fig. 1 in the specification sheets of the present invention is by this definition of mode directviewing description thermal shocking of solid solution temperature artwork; Fig. 1-A among Fig. 1 is the solid solution temperature artwork of routine; And Fig. 1-B, 1-C, three figure of 1-D are the representational solid solution temperature artwork of the present invention, and Fig. 1-B is a thermal shocking figure, and Fig. 1-C, 1-D are respectively secondary, three thermal shocking figure.
2 〉, the ultimate principle of thermal shocking formula solution treatment is: from the Metallkunde ultimate principle: this intensification is to impel solute dissolved process in matrix alloy the alloy, and it is then opposite to lower the temperature.Thermal shocking each time, " insulation-intensification of cooling-low temperature " operation each time promptly, the process of " dissolving-separate out " will inevitably take place once in solute thing in the alloy system mutually.Repeatedly concussion then " is dissolved-separate out " process back and forth, and this makes that the dissolving of solute phase-separate out passage is more unobstructed.For mutually smooth and easy the separating out of solute of solution treatment final step cold quenching and subsequently artificial inefficacy lays the foundation.Simultaneously, the repeatedly reciprocal dissolving-precipitation process of solute phase also can make the generation of solute phase produce hereditary effect to a certain extent.Become big in order to control the particle that the solute crystallization goes out, the minimum temperature of " dissolving-separate out " of the present invention operation, the minimum temperature in the cooling of the thermal shocking just operation, be controlled in thermal shocking top temperature 55%~75%.
In addition, from the thermodynamics ultimate principle, intensification can be regarded as to processed alloy energy is provided, and cooling then is to take out energy from system.The thermal shocking that " insulation-intensification of cooling-low temperature " operation is defined, essence are the energy thermal shockings of energy mode in a kind of increase or the minimizing system.This energy thermal shocking is carried out " storage " or " release " what move in circles to alloy, and the solute that may separate out in the alloy reaches the energy distribution equilibrium in this process, makes solute release energy in the isostatic mode and separate out in the ageing treatment stage.
For the rare earth heat-proof magnesium-base rare earth alloy, the rare earth addition accounts for finished product weight alloy per-cent and is generally 6% ~ 22%, and the rare earth that is added differs greatly at aspects such as atomic radius, fusing point and alloy substrate magnesium, cause formed ligancy be about 5 intermetallic compound often be in higher-energy state, more be of practical significance by thermal shocking release or balanced energy.
The step of the solid solution treatment method of a kind of heat-proof magnesium-base rare earth alloy of the present invention and condition are:
The composition of heat-proof magnesium-base rare earth alloy of the present invention and weight percent proportioning are: 8.2%Gd-2.8%Nd-0.4%Zr-Mg, Mg are surplus; Method of the present invention is that the solid solution treatment process of this alloy routine is improved.Water carried out cold quenching after 535 ℃ of insulations were shifted out heat treatment furnace after 10 hours in heat treatment furnace original alloy, and be improved to: heat-proof magnesium-base rare earth alloy solid solution temperature in heat treatment furnace reaches top temperature T
hBe 535 ℃ holding stage, increase once or once above thermal shocking; The described once operation of " insulation-intensification of cooling-low temperature ", the present invention is defined as a thermal shocking.
The concrete working method of a described thermal shocking is: in the temperature T of determining solution treatment
hWith soaking time t
hAfter, at the total soaking time ∑ of high temperature t
hUnder the constant prerequisite, increase " insulation-intensification of cooling-low temperature " operation, the total soaking time ∑ of this high temperature t in the solution treatment stage
hIt is 6~48 hours.
" cooling " operation in described " insulation-intensification of cooling-low temperature " operation: the lower-most point T that the temperature of " cooling " operation is reduced to
LBe T
h55~75%, the rate of temperature fall of cooling operation is 5~12 ℃/min.
" low temperature insulation " operation in described " insulation-intensification of cooling-low temperature " operation: the temperature T that reduces as far as possible during cooling is operated
LPlace's beginning " low temperature insulation ", low temperature soaking time ∑ t
LBe the total soaking time ∑ of high temperature t
h5~40%.
" intensification " operation in described once " insulation-intensification of cooling-low temperature " operation: vertex and T that " intensification " service temperature raises
hEquate that the temperature rise rate in this warming temperature is 2~10 ℃/min.
The thermal shocking that described increase is once or once above preferably increases the thermal shocking of 1 time, 2 times or 3 times, and preferred thermal shocking number of times is 2 or 3 times.
The cold quenching in solution treatment stage can adopt water-cooled, air cooling or water-soluble polymer solution cold quenching; Timeliness can adopt one-level timeliness, two-stage time effect or multistage aging.
Described cold quenching and timeliness are preferably: with the high-temperature heat-resistance magnesium-base rare earth alloy of coming out of the stove, drop into temperature and be in the water-soluble cross-linked sodium polyacrylate hydrogel of room temperature and be cooled to room temperature, then 230 ℃ of following artificial agings 24 hours.
Solid solution treatment method remarkable advantage of the present invention is: compare with the solution treatment of not carrying out thermal shocking, solid solution treatment method of the present invention can improve the room temperature of heat-proof magnesium-base rare earth alloy and 250 ℃ mechanical behavior under high temperature significantly, and the toughness aspect of especially improving alloy is more obvious.For example to consisting of the heat-proof magnesium-base rare earth alloy of Mg-8.2%Gd-2.8%Nd-0.4%Zr, increase by twice thermal shocking thermal treatment of the present invention after, the conventional heat treatment phase ratio with no thermal shocking has improved 1.55 times 250 ℃ of tensile strength; Its elongation has also improved 2 times.
Description of drawings:
Fig. 1 is conventional solid solution treatment process temperature schedule figure.
Fig. 2~4 are the temperature schedule figure of the representational thermal oscillation solid solution treatment process of novel method of the present invention.Wherein:
Fig. 2 is a thermal shocking solid solution treatment process temperature schedule figure.
Fig. 3 is time two thermal shocking solid solution treatment process temperature schedule figure.
Fig. 4 is three thermal shocking solid solution treatment process temperature schedule figure.
Embodiment
Embodiment 1:
Different is with Comparative Examples 1: increase a thermal shocking at the holding stage of solid solution treatment process, be quantitatively described in conjunction with 7 stages of Fig. 2.Is that 4 ℃/min rises to T from initial room temperature with temperature rise rate
h, this T
hBe 535 ℃, this is the 1. individual stage; At T
hTemperature kept 3 hours, i.e. t
H1Be 3 hours, this is the 2. individual stage; Then carry out thermal shocking and handle, carry out earlier being cooled to minimum holding temperature T with the rate of temperature fall of 8.8 ℃/min
L, T
LBe 325 ℃, make the ratio T of minimum holding temperature and the highest holding temperature
L/ T
hBe 61%, this is the 3. individual stage; 325 ℃ of insulations 0.4 hour, i.e. the holding stage of thermal shocking, this is the 4. individual stage; Be warming up to T with 7 ℃/min subsequently
hBe 535 ℃, promptly enter the temperature rise period of thermal shocking, this is the 5. individual stage; Be incubated 4 hours down at 535 ℃, this is the 6. individual stage; The 7. the cold quenching and the condition that artificial aging is subsequently handled in stage is all identical with comparative example.Remaining is with comparative example 1.The room temperature of the sample of gained and high temperature tension test result are:
Room temperature: tensile strength: 202MPa; Yield strength: 182MPa; Elongation: 2.2%.
250 ℃: tensile strength: 179MPa; Yield strength: 168MPa; Elongation: 4.6%.
Comparative Examples 1:
To the 8.2%Gd-2.8%Nd-0.4%Zr-Mg heat-proof magnesium-base rare earth alloy that consists of, wherein content is weight percentage (wt.%), and Mg is a surplus.The as cast condition heat-proof magnesium-base rare earth alloy is carried out solid solution and artificial aging processing.Select conventional solid solution treatment process, i.e. the holding temperature T of solution treatment
hBe 535 ℃, the total soaking time ∑ of corresponding high temperature t
hIt is 11 hours; Temperature rise rate with 8 ℃/min rises to T from room temperature
h, promptly 535 ℃, then 535 ℃ of insulations 11 hours.Sample is dropped in the water-soluble cross-linked sodium polyacrylate hydrogel again and be cooled to room temperature.Then 230 ℃ of following artificial agings 24 hours.Heat-proof magnesium-base rare earth alloy is carried out room temperature and high temperature tension test respectively, and the result is:
Room temperature: tensile strength: 188MPa; Yield strength: 162MPa; Elongation: 1.2%.
250 ℃: tensile strength: 161MPa; Yield strength: 112MPa; Elongation: 3.2%.
Embodiment 2:
Different is with embodiment 1: at T
hIncrease a thermal shocking in total soaking time of temperature, become twice thermal shocking, be quantitatively described in conjunction with Fig. 3.
Among Fig. 3 the 1. temperature rise rate in a stage is 4.7 ℃/min; 2. the individual stage is the holding stage t first time under 535 ℃
H1It is 1.45 hours; 3. the temperature-fall period that the individual stage is thermal shocking for the first time, its rate of temperature fall is that 8.5 ℃/min reduces to 320 ℃; 4. an individual stage is to be incubated 0.4 hour under 320 ℃ temperature; 5. an individual stage is that temperature rise rate is that 5.5 ℃/min is increased to 535 ℃; So far, thermal shocking for the first time finishes.6. the individual stage is the holding stage t second time under 535 ℃
H2It is 4 hours; The technology of thermal shocking for the second time is with for the first time identical.Enter holding stage t for the third time after the thermal shocking for the second time
H3, both 10. stages of the among Fig. 3.This stage is at 535 ℃ of following soaking time t
H3It is 1.75 hours; Cold quenching subsequently is all identical with embodiment 1 with the condition that artificial aging is handled.Remaining is with embodiment 1.The room temperature of the sample of gained and mechanical behavior under high temperature measurement result are:
Room temperature: tensile strength: 362MPa; Yield strength: 239MPa; Elongation: 8.4%.
250 ℃: tensile strength: 278MPa; Yield strength: 190MPa; Elongation: 9.2%.
Embodiment 3:
Different is with embodiment 2: directly be warming up to the highest holding temperature T from room temperature
h, at T
hBe to be increased to three thermal shockings in the total soaking time under 535 ℃, the timed interval of each thermal shocking has nothing in common with each other.Under 535 ℃ the first time holding stage soaking time t
H1Be 0.3 hour, t
H2Be 0.6 hour, t
H3Be 1 hour, t
H4It is 3.75 hours; Fig. 4 is the quantitative description synoptic diagram of its technology.Remaining is with embodiment 2.The room temperature of gained sample and mechanical behavior under high temperature measurement result are:
Room temperature: tensile strength: 234MPa; Yield strength: 177MPa; Elongation: 3.8%.
250 ℃: tensile strength: 199MPa; Yield strength: 164MPa; Elongation: 5.2%.