DE1583983A1 - Process for the production of plastically deformed bodies from alloys based on iron-rhodium - Google Patents

Description

158398c ghaelis. Horst student Dr. Erharf Ziegler

Patent attorney patent attorney patent attorney

6 Frankfurt / Main 1 6 Frankfurt / Main 1 ° Frankiurt / Main I ft »tfadi 3011 Taunusstr. 20 P.O. Box 3011 P.O. Box 3011

i I. FEB. Wed

793-RDCD-6M5 General Electric Company, 1 River Road, Schenectady, N.Y, USA

Process for the production of plastically deformed bodies from alloys based on iron-rhodium

The invention relates to alloys based on iron-rhodium, velahe possess a CeCl-like oriented crystal structure in the heat-treated state. These alloys can Can be used for calibration alone, or contain essential legal elements. You go through a transition from antiferromagnetic to ferromagnetic state, which depends on the exact composition of the

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Alloy occurs suddenly at different temperatures. In addition to the iron-rhodium binary alloys, which are, for example, in General Electric Research Report No. 61 RL 2870 M, Nov. 1961 * by Kouvel et al., Form iron-rhodium alloys as described in U.S. Patent Ho. 3,144,324 -Bither, Jr., dated August 11, 1964, and U.S. Patent No. 3,144,325 -Walter are disclosed August 11, 1964. Examples of iron-rhodium materials that are accessible to the * method of the present invention.

Although these alloys are useful because of their unique sudden transition from non-magnetic to magnetic states when heated, there are limitations in the manufacture of the alloy because of their extraordinary physical hardness. Although the intermetallic compound FeRh due to their Qefügeumwandlung first order at about 33O ⁰ K (57 ° C), where a> sudden change in the magnetization occurs, for example, as Messfflhlermaterial (sensor material) of

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Meaning, so use would be by fact limited that small samples either by thin film techniques, which samples without any sharp Generate OefUgewandungen, see Lomrael (J. Appl. Phys. 37, 1483 (1966)), or by machining

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or rolling an ingot must be produced.

Some of the advantages of this invention are readily apparent; Description and drawings explained.

In the drawings shows:

Figure 1 is a graphical representation of the magnetization (per gram) as a function of temperature, while clarifying, that opportunity as a highly cold-formed sample (ie filings) its steep magnetic transition by heating to about 235 ⁰ C (5iO ° K).

Figure 2 is a graph similar to Figure 1, in which the change in the nature of the magnetic Transition is illustrated by the method according to the invention.

In general, the invention relates to a method for producing plastically deformed bodies from alloys on iron-rhodium basis, in which a starting body initially up to a previously determined intermediate thickness by hot deformation and then from this intermediate thickness to the final desired thickness or shape reduced by cold working

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will. During the cold deformation _s must be the Mats-rial tempered between the individual stages to maintain the integrity of the material. After the material has been cold worked, there is no sudden magnetic transition. However, it has now been found that there is a steep transition in the machined material. can be hold by being a final heat · * not treatment under 235 ⁰ C and preferably not subjected to 425 ° C. Furthermore, the steepness of the transition can be preliminarily changed by the cold deformation of the tempered material depending on the degree of processing in different degrees until an essentially linear magnetic transition is obtained.

It has already been pointed out above that iron-rhodium and iron-rhodium with small amounts of others Alloy constituents are very hard materials and therefore, prior to this invention, no bodies with small dimensions were made from them by mechanical forming processes have been. This means that they were not created in the plastically deformed state. It was unexpectedly found that iron-rhodium-based alloys, if they are subjected to cold deformation, they differ from an ordered crystallographically space-centered cubic

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Arrangement in a misguided & ordered crystalline cubic Convert surface-centric arrangement. Vex ^ mutlioh is that Material in the cubic surface-centering state of cold working more accessible.

Qeraäss the method of the present invention, a Ouesblock first warmverforoit a Auegangekörper of an iron-rhodium material, for example to an elevated temperature, not less than 85O ⁰ C., and to a smaller thickness. This can be accomplished by various means such as hot rolling, hot milling or hot pressing. After being hot worked to any intermediate thickness, the material is then cold worked to a predetermined final thickness chosen. During the cold deformation, the material undergoes at least a partial structural transformation from the ordered body-centered cubic to the disordered face-centered cubic crystallographic arrangement. In this cold-worked state, the material does not have the steep transition from ant! Ferromagnetic »: to the ferromagnetic state, which is characteristic of tempered alloys based on bis-rhodium.

However, this steep magnetic transition can be obtained in the plastically deformed material when under 2 "55 ° C (51O ⁰ K) is not heated to a temperature. Preferably

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A much higher temperature should be used to on the one hand to accelerate the conversion from the cubic surface-centered to the cubic body-centered structure, and on the other hand to also improve the steepness of the magnetic transition.

In a specific example, a FeRh ingot with dimensions of 7.62 ram 7.62 mm 76.2 mm (Ο, 3 ^Μ χΟ, 3 "χ3") was cast and then in vacuum at 975 ^{0 to homogenize the composition} C remunerated for 26 hours. The homogenization can for example be carried out at temperatures in the range of about 850 and 1000 ⁰ C. The ousablook was then cut into three parts, each part measuring 7.62 mm by 7.62 mm by 25.4 mm. Two samples were tested at temperatures from 850 to 1000 ⁰ C at 1.27 mm (50 mils) hot forged and rolled, and the third piece was directly mn to 0.635 (25 mils) hot rolled. After hot rolling, the specimens were placed between stainless steel plates and brought to a final thickness of about 0.25 Na (10 rails) by cold packet rolling in rolling stages, the thickness being reduced by 5% in each case. The bundle rolling is not necessary, but represents a similar process in this bundle because of the comparatively small dimensions of the samples. Between the cold rolling stages, the samples were used for relaxation

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tempered at about 950 ° C.

After the completion of cold rolling, when the sample was examined, it was mainly found to have a face-centered cubic structure, with a little space-centered cubic structure remaining. Furthermore, showed an examination of magnetic properties with respect to a "temperature rise of the material to the temperature" in the usual the magnetic transition in PCP occurs, ie at 57 ° C (33O ⁰ C) ₁ more broad than a sharp transition. The a heat treatment, samples were then at about 1000 ⁰ C subjected. subsequent examination showed that the sharp magnetic transition characteristic dee PCP was regressed.

How the magnetic properties of the material are changed can be seen from the curves in the drawings. The temperature at which the FeRh-Baaielegierungen when heated normally change from the antiferromagnetic to the ferromagnetic state is (330 ⁰ K) at about 57 ° C. When the curve in Pig. 1 is followed from the point 10 in the directions of the display arrows, on the other hand, a strongly cold-worked sample of FeRh fur chips when cooled to a little less than 10O ⁰ K and subsequent heating according to the line 11 showed no magnetic transition at the

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Temperature at which this would normally occur. When heated to about 51O ⁰ K a kristallographieche structural transformation occurred when the material was converted by the face-centered cubic raumsentrierte in the structure, and corresponding to the line 12 entered a sudden change in the magnetization. A further increase in temperature to a little more than 70O ⁰ K caused the magnetization to drop to practically zero, as normally happens with a ferromagnetic material in the vicinity of its Curie temperature. A cooling of the material gave a magnetization curve corresponding to line 13 'that is, the magnetization increased, at about 330-3 ^ O ⁰ K has reached a maximum, and then the magnetization fell rapidly until they practically at a temperature of about 200 to 25O ⁰ K disappeared. If a sample with this behavior was heated again, roughly corresponding to line 14, it went through a magnetic transition at roughly the same temperature, which is characteristic of heavily tempered iron-rhodium material. The dotted curve 20 shows the steep magnetic change that occurred in other iron-rhodium bodies that were rapidly cooled to room temperature ^{after a heat treatment at 1000 ° C.}

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While the steep magnetic transition is extremely important in many applications, there are certain circumstances where a different and gradual transition is significantly preferable. It has been found that FeRh material which has been treated as described above in such a way that it has a steep magnetic transition can be further treated in order to change the fundamental character of the transition. In particular in the case of further plastic deformation of the tempered material, in which the thickness is reduced by up to 50% , the magnetization increases linearly with the temperature.

This characteristic can best be seen from Figure 2 of the drawings, in which curve 25 represents the steep magnetic transition in a thoroughly quenched and tempered FeRh alloy. Curve 26 shows how the transition becomes flatter when the alloy is cold worked about 30 % after the tempering. Curve 27 shows the increased effect with cold deformation of 50 %. After about 50 years of deformation, the magnetic transition became practically linear.

For the first time, the present procedure has a method * with which “a characteristically hard material with unique magnetic properties is plastically deformed

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Bodies can be processed and then further treated, so that as the established magnetic properties owns.

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Claims (5)

- "· 158398S claims 1. A process for the production of plastically deformed bodies from alloys based on iron-rhodium with a steep magnetic transition, characterized in that a starting body made of the base alloy is reduced to a preselected final dimension by hot and cold deformation, with intermediate annealing between the cold deformation stages as desired are used, whereby the base alloy undergoes a crystallographic transition into a misoriented cubic face-centered structure by cold working, and that the cold-worked alloy with the final dimensions is ^{subjected to a heat treatment at a temperature not below 235 °} C. for a sufficiently long time, in such a way that the ordered body-centered cubic structure is created with a steep magnetic transition. 2. The method according to claim 1, characterized in that the hot and cold deformation duroh Forging and rolling takes place. i'iCi.ivnL Ii »lot i -« - »ii-i- ' 009842/0340 3. The method according to claim 1 or 2, characterized in that the hot forming is carried out at temperatures in the range between 850 and 100O ⁰ C. 4. The method according to claims 1-3, characterized in that the heat treatment of the cold-worked alloy at temperatures not below 25 ° C is carried out. 5. The method according to claims 1- ¹ I, characterized in that a flattening of the magnetic transition is made in that the thickness of the body with the steep magnetic transition is reduced by additional cold deformation by up to 50 % . 0098A2 / 03A0 Blank page