CN1049382A - Alloy containing iron, manganese, silicon and nickel by form memory - Google Patents

Abstract

Fe-Mn-Si-Ni is advantages such as polycrystalline shape memory alloy smelting technology is simple, and cost is low, and cold and hot working is good.In the hot rolling attitude, do not need through any other processing, this alloy can obtain shape memory effect almost completely in-196～50 ℃ of temperature ranges.By certain thermomechanical treatment, its memory performance can obtain obvious improvement.This alloy has high strength, high tenacity, no magnetic is anti-corrosion, anti-low temperature.Thereby, in automatic control, machinofacture, fields such as techniques for ultra-low temperature can be expected to use widely.

Description

Iron-manganese-silicon-nickel series shape memory alloy

The Fe-Mn-Si-Ni series shape memory alloy belongs to the field of processing and manufacturing functional materials, structural materials and non-magnetic materials.

Shape memory alloys have entered the stage of commercialization to a certain extent. At present, related products at home and abroad are mainly made of Ni-Ti memory alloy and Cu-based memory alloy. These alloys still have many shortcomings and deficiencies in the smelting and manufacturing process; Ni-Ti alloys have excellent memory properties. However, the smelting process of this alloy is complicated, the phase transition temperature is difficult to control, and the price is expensive; the copper-based memory alloy makes up for the deficiency of the Ni-Ti alloy to a certain extent. The overheating ability is poor. Fe-Mn-Si alloys also have a good shape memory effect (A. Sato, et al, Acta. Metall. 3249847.539). Judging from the current reports, the alloy also has disadvantages such as poor processability and high requirements for smelting conditions. Therefore, the above-mentioned alloys are largely difficult to popularize and apply on a large scale.

In order to develop economical, practical and high-strength shape memory alloys. The invention proposes Fe-Mn-Si-Ni polycrystalline shape memory alloy.

Shape memory alloys undergo two phase transformations within a certain composition range: one is austenite (r)martensite (ε) phase transformation, and when in the state of the parent phase austenite, an external force is applied. Induce r→ε transition, followed by macroscopic shape strain; after heating. The original shape can be restored by means of ε→r reverse transformation. That is, the shape memory effect (referred to as SME) is generated; another phase transition is the transformation of paramagnetic austenite (r) and antiferromagnetic ordering (r). This magnetic transition suppresses the r→ε phase transition, thereby reducing the memory function of the alloy.

When designing the composition of Fe-Mn-Si-Ni alloy, the effects of these two phase transitions on SME must be fully considered. When the total content of Mn, Ni and Si is too low, the r→ε phase transition temperature M _s is too high, which not only deteriorates the memory performance of the alloy, but also is not conducive to practical application. Conversely, if the total content of Mn, Ni, and Si is too high, M _{s is} much lower than room temperature, so the antiferromagnetic ordering transition temperature may be higher than room temperature, making the parent phase r too stable for the stress-induced ε martensitic phase, so It is also difficult to obtain a good shape memory effect. When the Mn content is constant, the Si content cannot be higher than 6%, otherwise the alloy will become very brittle and difficult to process. After testing and synthesis, the present invention considers that when selecting the composition of Fe-Mn-based memory alloy, it mainly considers the following aspects. ① Avoid stress-induced r→α martensite transformation. ② Improve parent phase strength. ③Inhibit the transformation of antiferromagnetic order, ④Inhibit the formation of quenched ε martensite, so that r is in a metastable state.

The Fe-Mn-Si-Ni series alloy composition scope that the present invention develops is

Mn: 22-27% (both by weight percentage)

Si: 1-6%

Ni: 1 to 4%

Fe: margin

C: <0.02%

S.P total content <0.01%

The total amount of O ₂ N ₂ H ₂ <200PPm

The alloy is smelted and poured in an electric induction heating boiler under normal pressure. After high-temperature homogenization annealing, it is hot-forged at 800-1100°C to form a 7mm-thick plate, and then hot-rolled at 1050°C to form a 2mm-thick sheet. The alloy can also be cold rolled or cold drawn.

The SME of the alloys was evaluated using the measurement of the bending angle of the sheet specimens. The 1×2×60mm sheet sample is evenly bent 180° on a special mold, and the maximum deformation on the receiving and pressing surfaces is greater than 5%. The bending angle after bending unloading is denoted as θ _e , and when heated to temperature T, the bending angle decreases to θ _T , then the shape recovery (SR) at T temperature is: $\mathrm{SR}=\frac{{\mathrm{\&theta;}}_e-{\mathrm{\&theta;}}_T}{{\mathrm{\&theta;}}_e}\&times;100\%$ The maximum value of SR is denoted as SME and the alloy exhibits a one-way shape memory effect. When the deformation is less than 2-3%, the alloy can obtain complete SME in the hot-rolled state without any other heat treatment. By changing the content of Mn, Si, Ni alloy elements. It is easy to adjust and control the phase transition temperature M _s and T _N ^r in the range of -50 to 100°C. Deformation can be performed in the range of -196 to 100°C, and better SME can be obtained. If the hot-rolled sample is Further deformation heat treatment is carried out. Its memory performance can be significantly improved. Deformationheating cycle treatment tests show that after a few cycles of treatment, the attenuation trend of the memory performance of the alloy tends to be stable. In addition, heating and quenching methods, recovery heating methods, and time have no obvious impact on the memory performance of the alloy.

The alloy has good mechanical properties at room temperature, low temperature, and ultra-low temperature. At room temperature, the alloy: σ _s = 100 ~ 140MPa, σ _b = 700 ~ 900MPa,  > 40 ~ 50% The alloy is corrosion-resistant, non-magnetic, and resistivity temperature The coefficient dp/dT is small, and dp/dT≈0 near T _N ^r temperature

The development and research of Fe-Mn-Si-Ni memory alloy has two meanings. On the one hand, in theory, its research will further enrich and develop the theory of shape memory alloys and martensitic phase transition. On the other hand, this alloy has greater practical application value. Therefore, it is difficult to popularize and apply it on a large scale. The main reason is that the manufacturing cost of memory alloys in the past is expensive. rough estimate. The cost of Cu-based memory alloy is about an order of magnitude lower than that of Ni-Ti alloy, and this alloy is only about 1/3 of that of Cu-based alloy, and its production does not require special smelting and manufacturing technology.

In summary, Fe-Mn-Si-Ni alloys have excellent memory performance, mechanical properties, and physical properties. Thus, a wide range of applications can be expected in many technical fields according to performance requirements. For example, it is used to make temperature control components, fasten shockproof bolts, pipe joints, precision resistance alloy components, and ultra-low temperature non-magnetic steel components. Taking Fe-25.38Mn-3 and 47Si-2.98Ni as examples to illustrate the memory function of the alloy, the M _s of the alloy is about 50°C, and the antiferromagnetic transformation ordering ordering temperature T _N ^r = -43°C, σ _s = 110MPa σ _b /σ _s = 7.89  = 60%; when the tensile deformation is ≤ 2%, in the temperature range of -196 ~ 25 ℃, after hot rolling and air cooling, without any other treatment, it has complete SME; When the maximum bending deformation is 5%, SME=80%;

The hot-rolled sample was stretched and pre-deformed by 15% at 250°C, and then annealed at 650°C for 10 minutes. When the maximum bending deformation was 5%, the SME at room temperature could be increased to more than 90%.

Claims (1)

1. A shape memory alloy, characterized in that the alloy consists of the following components Mn: 22-27% Si: 1-6% Ni: 1-4% Fe: margin C: <0.02% The total amount of O ₂ N ₂ H ₂ is <200ppm. S.P total content <0.01%.