CN1667144A - Preparation of NiAl Shape Memory Alloy Thin Films by Alloying Ultrathin Laminates by Cold Rolling - Google Patents

Abstract

This invention discloses a method of preparing NiAl shape memory alloy thin film through cold rolling ultrathin lamination alloying. Good plasticity, easy deformed Al foil, Ni foils are materials, and foil thickness is defined according to atom constitution formula Ni1-XAlX. Metal foils are alternating laid, sandwich structure is got after big deformation cold rolling, it is repeated again and again, and finally components uniform alloy film is got after diffusion annealing alloying. The reactant ratio is 0.30<=x<=0.40. The film components made by this method is easy control, crystal grain is small, fatigue life is high, area is large and cost is low.

Description

Preparation of NiAl Shape Memory Alloy Thin Films by Alloying Ultrathin Laminates by Cold Rolling

technical field

The invention relates to the field of shape-memory alloys, in particular to a method for preparing NiAl shape-memory alloy films by cold-rolling ultra-thin lamination alloying. The thin film prepared by the method has the advantages of simple production process, easy control of components and good mechanical properties.

technical background

Most of the shape memory alloys used today are affected by their thermoelastic martensitic phase transition temperature, and their working temperatures are mostly lower than 100°C. There is particular interest and demand for high temperature shape memory alloys with higher phase transition temperatures. Therefore, the research and development of high-temperature shape memory alloys has considerable engineering application prospects, and will definitely help to upgrade automation and self-adaptive capabilities in the field of engineering technology in the next century.

At present, the high-temperature shape memory alloys mainly include: CuAlNi series, NiTi series, and NiAl series. The service temperature of CuAlNi alloy is only about 150°C-200°C, which limits its use in a higher temperature range, and currently has the disadvantages of difficult cold working, coarse grains, and low fatigue life. On the basis of NiTi alloy, adding alloy elements such as Pd, Pt, Au, Zr and Hf can increase the phase transition temperature to above 500 °C, but the cost is extremely expensive, which limits its application range.

The Ms point of the NiAl alloy with a Ni content of 60-70 at% can vary between -150 and 900 °C depending on the Ni content. Since the alloy contains a large amount of Al, it exhibits good high temperature oxidation resistance and thermal conductivity. In addition, as a high-temperature shape memory alloy, NiAl also has a high melting point (about 250 ° C higher than that of Ni-based superalloys), low density (about 2/3 of Ni-based superalloys), and good thermal conductivity (4 times that of Ni-based superalloys). -8 times) advantages, is considered to be one of the high-temperature shape memory alloys with the greatest development potential.

Compared with other high-temperature shape memory alloys, NiAl has obvious advantages and should be widely used. However, since NiAl is an intermetallic compound, like most intermetallic compounds, it can hardly be plastically deformed at room temperature, which seriously hinders its practical application. In order to improve its room temperature brittleness, predecessors have adopted a variety of methods, such as alloying, grain refinement and so on. Alloying method, such as adding Fe, Mn and other elements, forms a γ phase with good plasticity, but the formation of γ phase causes the martensitic transformation temperature Ms point to be greatly reduced, and at the same time weakens the shape memory effect; at the same time, the second The formation of phases, reducing the content of Al in the alloy, will reduce the oxidation resistance of the alloy, weaken the advantages of NiAl as a high-temperature shape memory alloy, and have not significantly solved the key problem of room temperature brittleness of NiAl alloys, and NiAl cannot be prepared by cold rolling at all. alloy film. Thin-film drive elements will be a major field of application of shape memory alloys.

This is because the driving of shape memory alloys is excited by heat, so the response frequency of bulk shape memory alloys is low, only 1HZ, which is several orders of magnitude lower than other driving materials such as piezoelectric materials and magnetostrictive materials. In order to increase the response frequency of the shape memory alloy, a film with a large specific surface area and a strong heat dissipation capability must be used. In order to prepare CuAlNi-based alloy thin films, a rapid solidification method is used. Although this method can obtain a NiAl alloy film with a thickness less than 100 μm, the film is limited by its width and is not suitable for industrial production.

The recently developed method of cold-rolling ultra-thin lamination alloying to prepare alloy thin films enables us to use existing conventional rolling equipment to prepare NiAl shape memory alloy thin films in large areas at low cost. This method uses pure metal or alloy foil with good plasticity and easy deformation as the raw material. The thickness of the foil is determined according to the designed composition ratio, and the metal foils are placed alternately. After large deformation cold rolling, an ultra-thin laminated sandwich structure is obtained. If necessary, the cold-rolled ultra-thin laminate can be folded in half and then cold-rolled again, and so on, and finally alloyed by diffusion annealing to obtain an alloy film with uniform composition. Its production process is shown in the attached drawing.

Contents of the invention

The purpose of the present invention is to provide a method for preparing large-area, low-cost NiAl shape memory alloy thin films through cold rolling ultra-thin lamination alloying method using conventional rolling equipment.

The atomic composition formula of the NiAl shape memory alloy thin film is Ni _1-x Al _x , and its composition ratio satisfies 0.30≤x≤0.40.

The method of preparing large-area NiAl shape memory alloy film by cold-rolling ultra-thin lamination alloying: according to the designed atomic composition ratio, nickel foil and aluminum foil are used as raw materials, alternately stacked and placed, and an ultra-thin lamination sandwich is obtained after large deformation cold rolling According to the needs, the cold-rolled ultra-thin laminate can be folded in half and then cold-rolled again, and so on. Finally, the diffusion annealing is carried out with heat preservation in the temperature range of 673K-923K to obtain an alloy thin film with uniform composition. In order to make the thin film have a shape memory effect, the alloyed thin film needs to be subjected to a beta treatment of solid solution and quenching above 1373K.

Compared with prior art, the present invention has following advantage:

1) For the first time, NiAl shape memory alloy film was prepared by cold rolling alloying method, which solved the problem that NiAl alloy was difficult to prepare and process at room temperature due to its brittleness. The film prepared by it has good shape memory effect and plasticity, and can meet the requirements of being a driving material.

2) Large-area NiAl shape memory alloy films can be prepared. The melt quenching and sputtering methods can only prepare small-area thin films, but the cold-rolled ultra-thin laminated alloying method can produce thin films with a width greater than 50 mm and a length of several meters to tens of meters, which is suitable for large-scale industries. Production.

3) The prepared NiAl shape memory alloy film has good plasticity and high fatigue life. The NiAl alloy thin film prepared by cold-rolled ultra-thin lamination alloying has fine grains, only a few μm, which is an order of magnitude lower than the current alloy grains, so it has better plasticity and higher fatigue life.

4) The prepared film has the characteristics of low cost and high performance. Because the component has good cold deformation ability, it can be produced by using existing cold rolling equipment, and does not require expensive special equipment, so the cost is relatively low. Has strong market competitiveness.

Description of drawings

A schematic diagram of a processing route for preparing a NiAl shape memory alloy thin film by cold-rolling ultra-thin lamination alloying in the present invention.

Detailed ways

The atomic composition formula of the NiAl shape memory alloy thin film prepared by the invention is Ni _1-x Al _x , and its composition ratio satisfies 0.30≤x≤0.40.

Studies have shown that when the Ms point of the binary NiAl alloy is higher than 530K, the transformation of martensite to Ni ₅ Al ₃ phase will be prior to the reverse transformation of martensite. Therefore, to make the binary NiAl alloy have a shape memory effect, the alloy The Ms points must be below 530K. But if the Ms point is too low, the alloy will lose its application value. Thus in a preferred embodiment, 0.355≦x≦0.37.

Example 1

According to the designed composition formula Ni _0.63 Al _0.37 , Ni foil with a thickness of 0.180mm and Al foil with a thickness of 0.160mm are used as raw materials, and 10 layers are placed alternately. First cold rolling to 1.200mm with a deformation of 65%, and then cold rolling to 0.080mm, the cold rolled film is folded and overlapped, and then cold rolled to 0.080mm, and so on for 10 passes. Finally, the cold-rolled 10-pass film was kept at 773K for 50 hours for alloying. The alloyed film was reheated to 1373K, kept warm for 0.5 hours and quenched in water. The Ms point of the alloy was determined to be 271K by the resistance method, and the shape was completely restored after bending at 243K with 3% heating.

Example 2

According to the designed composition formula Ni _0.635 Al _0.365 , Ni foil with a thickness of 0.140mm and Al foil with a thickness of 0.122mm are used as raw materials, and 10 layers are alternately stacked. First cold rolling to 1.000mm with a deformation of 62%, and then cold rolling to 0.080mm, the cold rolled film is folded and overlapped, and then cold rolled to 0.080mm, and so on for 10 passes. Finally, the cold-rolled 10-pass film was kept at 873K for 30 hours for alloying. The alloyed film was reheated to 1423K, kept warm for 0.3 hours and water quenched. The Ms point of the alloy was determined to be 342K by the resistance method, and the shape was completely recovered after being bent at room temperature by 3% and heated.

Example 3

According to the designed composition formula Ni _0.64 Al _0.36 , Ni foil with a thickness of 0.140mm and Al foil with a thickness of 0.119mm are used as raw materials, and 10 layers are placed alternately. First cold rolling to 0.800mm with a deformation of 69%, and then cold rolling to 0.050mm, the cold rolled film is folded and overlapped, and then cold rolled to 0.050mm, repeating 10 passes. Finally, the cold-rolled 10-pass film was kept at 923K for 20 hours for alloying. The alloyed film was reheated to 1473K, kept warm for 0.25 hours and water-quenched. The Ms point of the alloy was determined to be 419K by the resistance method, and the shape was completely recovered after being bent at room temperature by 3% and heated.

Example 4

According to the designed composition formula Ni _0.645 Al _0.355 , Ni foil with a thickness of 0.120 mm and Al foil with a thickness of 0.100 mm are used as raw materials, and 10 layers are placed alternately. First cold rolling to 0.800mm with a deformation of 64%, and then cold rolling to 0.040mm, the cold rolled film is folded and overlapped, and then cold rolled to 0.040mm, repeating this 10 times. Finally, the cold-rolled 10-pass film was kept at 923K for 20 hours for alloying. The alloyed film was reheated to 1523K, kept warm for 0.25 hours and water quenched. The Ms point of the alloy was determined to be 492K by the resistance method, and the shape was completely recovered after being bent at room temperature by 3% and heated.

Example 5

According to the designed composition formula Ni _0.645 Al _0.355 , Ni foil with a thickness of 0.180mm and Al foil with a thickness of 0.150mm are used as raw materials, and 10 layers are placed alternately. First cold rolling to 1.000mm with a deformation of 70%, and then cold rolling to 0.060mm, fold the cold rolled film in half, and then cold rolling to 0.060mm, repeating 10 passes. Finally, the cold-rolled 10-pass film was kept at 923K for 20 hours for alloying. The alloyed film was reheated to 1573K, kept warm for 0.2 hours and water-quenched. The Ms point of the alloy was determined to be 488K by the resistance method, and the shape was completely restored after being bent at room temperature by 3% and heated.

Claims (7)

1, a kind of NiAl shape memory alloy film of cold rolling superthin laminated alloying preparation is characterized in that the atom composition formula is Ni _1-xAl _x, ratio of components satisfies: 0.30≤x≤0.40.

2, a kind of method for preparing the described NiAl shape memory alloy film of claim 1 is with pure metal Al paper tinsel, and metal Ni paper tinsel is starting material, presses atom composition formula Ni _1-xAl _xDetermine the thickness of paper tinsel, the tinsel intermeshing is placed, cold rolling compound with gross distortion, as required, can be with gross distortion is cold rolling again after the superthin laminated doubling of cold rolling compound, so repeatedly, obtain the film of required thickness,, be incubated in 673K～923K temperature range at last with the superthin laminated film of cold rolling compound, the diffusion annealing alloying obtains the uniform alloy firm of composition.In order to make film have shape memory effect, the film after the alloying also need carry out the βization processing that the above solid solution of 1373K adds quenching.

3, the preparation method of shape memory alloy film according to claim 2 is characterized in that Ni _1-xAl _xRatio of components satisfies 0.355≤x≤0.37.

4, the preparation method of shape memory alloy film according to claim 2 is characterized in that cold rolling compound tense deflection is 50%～99%.

5, the preparation method of shape memory alloy film according to claim 2 is characterized in that the paper tinsel with pure metal Al, and metal Ni paper tinsel is starting material.

6, the preparation method of shape memory alloy film according to claim 2, the temperature that it is characterized in that diffusion annealing is 773K～923K, soaking time is 20～50 hours.

7, the preparation method of shape memory alloy film according to claim 2, the temperature that it is characterized in that the βization processing is 1373K～1573K, soaking time is 0.2～0.5 hour.