EP1436437B1 - Procédé de fabrication d'un alliage cu-zn-al6% à mémoire de forme à faible temperature de transformation martensitique - Google Patents

Procédé de fabrication d'un alliage cu-zn-al6% à mémoire de forme à faible temperature de transformation martensitique Download PDF

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Publication number
EP1436437B1
EP1436437B1 EP01978810A EP01978810A EP1436437B1 EP 1436437 B1 EP1436437 B1 EP 1436437B1 EP 01978810 A EP01978810 A EP 01978810A EP 01978810 A EP01978810 A EP 01978810A EP 1436437 B1 EP1436437 B1 EP 1436437B1
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EP
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Prior art keywords
temperature
shape memory
transformation temperature
martensitic
zinc
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EP01978810A
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German (de)
English (en)
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EP1436437A2 (fr
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Vijay Rajaram Harchekar
Madanlal Singla
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Council of Scientific and Industrial Research CSIR
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Council of Scientific and Industrial Research CSIR
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    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C9/00—Alloys based on copper
    • C22C9/04—Alloys based on copper with zinc as the next major constituent
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22F—CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS
    • C22F1/00—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working
    • C22F1/08—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of copper or alloys based thereon

Definitions

  • the present invention relates to Cu-Zn-Al(6%) shape memory alloy having a low martensitic transformation temperature and a process of lowering the martensitic transformation temperature.
  • Cu-Zn-Al Shape Memory Effect (SME) alloys are promising smart and intelligent engineering materials. (Wayman C.M., Journal of Metals, 32 (June 1980), p-129-137 and
  • nitinol has superior properties, long fatigue life and is biocompatible.
  • Shape memory alloys have a unique property i.e. these materials remember their past shapes/ configurations.
  • the Important characteristics of these alloys are their ability to exist in two distinct shapes or configurations above or below a certain critical transformation temperature. It undergoes diffusionless martensitic transformation Golestaneh A.A., Physics Today, (April 1984), p-62-70, which is also thermo elastic in nature i.e. below the critical temperature a martensitic structure forms and grows as the temperature is lowered, whereas, on heating the martensite shrinks and ultimately vanishes.
  • the martensite in shape memory alloys is soft in contrast to martensite of steels. Deformation of these alloys is not by slip, twinning or grain boundary sliding but by growth or shrinkage of self-accommodating, multi-oriented martensitic plates/variant Saburi T., Wayman C.M, Takala K & Nenno S., Acta Metallurgica (Jan 1980) P-15.
  • the strained martensite On heating, the strained martensite reverts back to its parent phase, thereby, the original undeformed shape is recovered.
  • the change in structure can be linked with change in shape and dimensions and the alloy exhibits a memory of high and low temperature shapes. There is a usable force associated with these shape changes and thus the alloys can be incorporated into range of temperature sensitive devices for warning, control, detection, regulation etc .
  • the actuators can be calibrated to operate within a narrow temperature range by incorporating a compensating bias spring.
  • the recoverable strain is 2-8% and is dependent upon one or two way memory.
  • Copper based shape memory alloys in addition to one-way memory also exhibit two-way memory behavior, after undergoing a suitable thermal-mechanical processing called training (Wayman C.M., Journal of Metals, 32 (June 1980), p-129-137 and Michael A.D & Hart W.B Metal Material Technol., 12(1980), p-434-440.
  • shape memory effect lies in the Copper rich corner of the triangle in the form of a trapezium.
  • This trapezium we can correlate composition with martensitic transformation temperature Schetky L.M., Scientific American, 241 (Nov. 1979), p-68-76.
  • the amount of Aluminum varies from 4-10%, Zinc from 10-30% and balance is Copper. Martensite formation temperature ('Ms') varies from -100°C to +300°C as a result of very small change in composition. But, useful range for Aluminum brass is -70°C to +150°C.
  • Martensitic transformation temperature is extremely sensitive to composition. A slight variation of either of the elements, Zinc or Aluminum (say ⁇ 0.5%) shifts the transformation temperature by ⁇ 50°C. Therefore close control of composition is utmost essential to get the desired transformation temperature for the actuator to work at a specific temperature. Loss of low melting and volatile elements like Al, Zn etc. while melting cannot be avoided in air melting furnaces. Vacuum melting furnaces, in which close control of composition is possible but their installation is extremely costly and are unaffordable to the small and medium scale melting units/industries.
  • the present invention is directed towards increasing or decreasing of martensitic transformation temperature.
  • Vacuum furnaces precisely control these losses but their installations are costly and are thus unaffordable to the small and medium scale melting/ foundry units.
  • Cu-Zn-Al shape memory alloys SMA's are no exceptions to these.
  • the martensitic transformation temperature (As) is an important parameter in shape memory alloys and is extremely sensitive to the composition. A slight variation of either zinc or aluminum ( ⁇ 0.5%), as a result of melting losses, shifts the martensitic transformation temperature by ⁇ 50°C. The material thus cast and processed reduces to a scrap & has to be remelted thereby resulting in wastage of efforts, manpower and machinery.
  • the object of the present invention is to provide for an improved process, in order to lower the transformation temperature of Cu-Zn-6Al shape memory alloys, by a low temperature re-betatising treatment from 110°C to 30°C i.e. a lowering of 80°C.
  • the present invention relates to a process according to the appended claims.
  • the present invention provides for a process for lowering the Martensitic Transformation Temperature(As) of shape memory alloy as claimed in claim 1.
  • the charge consisting of commercially pure Copper, Zinc & Aluminum was melted in an induction furnace under a charcoal cover and cast into sand moulds in plates of sizes 150 x 100 x 12.5 mm. These were then homogenized at 800 °C for two hours and cooled. These were then surface machined to remove oxidized layer. These homogenized plates were analyzed for chemical composition. The plates (12mm thick) were reheated at 750°C for one hour and hot rolled down to one-mm thick flat sheets with number of reheating in-between the reduction passes. These sheets were held in fixtures (1.0-mm thick sheets) and were betatised at 750°C for 3 minutes and then cold (ordinary) water quenched.
  • Martensitic structure prevailed between 500°C to 700°C.
  • seven more betatised samples were further reheated (rebetatised) at 550°C, 575°C, 600°C, 625°C, 650°C, 675°C, 700°C (increments of 25°C) for ten minutes and cold water (room temperature) quenched.
  • Their microstructures were observed (Fig.-4) These were deformed and their S.M. response & transformation temperatures were determined (Fig.-5,6).
  • a betatised sample, rebetatised at 575°C for ten minutes and water quenched was martensitic with enough alpha at the grain boundaries & within the grains, showed good shape memory response and its transformation temperature (As) was around 30°C.
  • An initial temperature of 110°C was thus lowered to 30°C by this two-step treatment, a drop of temperature of 80°C by this process.
  • Any intermediate transformation temperature can be achieved by selecting appropriate re-betatising temperature.
  • the process of re-betatising was repeated number of times, to ascertain the reproducibility and for the confirmation of results.
  • alpha solid phase exists up to 39% zinc content.
  • This ⁇ -phase has face centered cubic structure (FCC). It is ductile, malleable and cold workable. Above 39% Zinc to 50% zinc content a beta phase ( ⁇ ) appears. It has body centered cubic structure (BCC). It is a hard phase and can only be hot worked. Above 50% zinc content a complex, brittle and undesirable gamma ⁇ phase structure is formed.
  • Cu-Zn-Al is a ternary alloy system. It is basically a Cu-Zn alloy system with an addition of 3 rd element Aluminum. The zinc equivalent of Aluminum is six that is.
  • the 43% Zinc content lies very close to or almost on the phase boundary regions of ⁇ and ⁇ i.e. in the ⁇ rich, regions of the diagram. Keeping in view their conditions relevant experiments were carried out.
  • the alloy to 750°C the structural transformation is from martensite to beta, as such, we will designate this heating treatment as betatising and the transformation temperature as As (while heating) & Ms (while cooling) respectively.
  • the betatised material 750°C /3 min./CWQ
  • the previously high temperature betatised samples (6 Nos.) were rebetatised at low temperature to 200°C, 300°C, 400°C, 500°C, 600°C and 700°C for ten minutes and cold water (room temperature) quenched. Their microstructures, shape memory response and martensitic transformation temperatures were determined.
  • Rebetatised 200°C material was martensitic. But was very stiff, as quenching from 200°C and as such did not show shape memory.
  • Rebetatised 300°C sample had ⁇ + ⁇ little martensite. It was stiff and had no memory. The morphology of ⁇ was rod or plate type.
  • Rebetatised 400°C sample too was stiff with no SME. It contained ⁇ + ⁇ structure and ⁇ -Phase was within the grains.
  • the rebetaised 500°C material was soft but had no SME. Its structure was ⁇ + ⁇ very little martensite. It had very thin ⁇ -phase rim at the grain boundaries, which had tendency towards globular form.
  • the samples heated at 600°C and 700°C were soft and deformable and showed memory of low & high temperatures respectively. These materials were fully martensitic but 600°C rebetatised sample had little ⁇ -precipitated at the grain boundaries and within the grains as compared to 700°C sample.
  • the 700°C sample was comparatively fine grained. These materials did not crack even on cold water quenching. By these specific experiments it was ascertained that shape memory effect in this material was between 550°C to 700°C.
  • betatised strips were taken and were subjected to re-betatising treatments at 550°C, 575°C, 600°C, 625°C, 650°C 675°C and 700°C (an increment of 25°C) for ten minutes and then cold (room temperature) water quenched.
  • Microstructures, shape memory response, and transformation temperatures were evaluated.
  • the 550°C betatised sample was soft and its transformation temperature had dropped from 110°C to 22°C
  • the sample had a feeble memory mainly because of separation of sufficient volume fraction of ⁇ -phase in ⁇ and very little visible martensite. Grain boundary ⁇ -envelop was also thick.
  • Sample rebetatised at 575°C was soft and had good shape memory 30°C.
  • Samples rebetatised at 625°C was also soft and has good SME around 61°C. Structure was martensitic with unresolved ⁇ -phase at the grain boundaries.
  • the sample rebetatised at 650°C, 675°C and 700°C were all soft and had shape memory at 79°C, 100°C & 110°C respectively (Fig.-7,8). These were fully martensitic and there was hardly any ⁇ visible at grain boundaries & within the grains. In other wards ⁇ -phase was not resolvable. Since very little or negligible ⁇ -phase has separated from the martensite matrix, these samples showed shape memory at high temperatures.
  • Martensite transformation temperature (As) can be lowered substantially by about 80°C in Cu-Zn-6% Al alloys by specific thermal treatment i.e. by low temperature re-betatising of the previously high temperature betatised material.
  • the decrease of temperature was mainly due to the separation of small quantities of alpha ( ⁇ ) from the matrix of martensite.
  • This retained ⁇ -phase does not affect the shape memory response but in turn, it assists in cushioning the grain boundaries & thereby preventing the material from cracking, even on quenching in cold water.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Manufacture And Refinement Of Metals (AREA)
  • Adornments (AREA)
  • Superconductors And Manufacturing Methods Therefor (AREA)

Claims (3)

  1. Procédé pour diminuer la température de transformation martensitique (As) d'alliages à mémoire de forme Cu-Zn-Al, comprenant :
    (i) la sélection d'un alliage comprenant du zinc dans l'intervalle allant de 10 à 28% et 6% d'aluminium, le reste étant du cuivre,
    (ii) la fusion de la composition d'alliage dans un four à induction, fonctionnant à l'air sous couverture de charbon, puis coulée en les formes souhaitées ;
    (iii) l'homogénéisation de la composition ci-dessus à 800°C pendant une période d'environ 2 heures, puis refroidissement ;
    (iv) l'usinage de la surface pour éliminer la formation d'écailles d'oxyde ;
    (v) l'analyse de la composition d'alliage ;
    (vi) la betatisation du matériau formé par chauffage à 750°C pendant trois minutes et la trempe avec de l'eau froide, et
    (vii) le rebetatisation du matériau betatisé par chauffage à une température de 575-700°C pendant 10 minutes et la trempe avec de l'eau froide.
  2. Procédé selon la revendication 1, dans lequel la rebetatisation est réalisée à 575°C.
  3. Procédé selon la revendication 1 ou 2, dans lequel la température de transformation martensitique (As) est diminuée à 30°C par rapport à la température précédemment élevée de 110°C.
EP01978810A 2001-10-22 2001-10-22 Procédé de fabrication d'un alliage cu-zn-al6% à mémoire de forme à faible temperature de transformation martensitique Expired - Lifetime EP1436437B1 (fr)

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PCT/IN2001/000186 WO2003035918A2 (fr) 2001-10-22 2001-10-22 Alliage cu-zn-al(6%) a faible temperature de transformation martensitique et procede associe

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EP1436437A2 EP1436437A2 (fr) 2004-07-14
EP1436437B1 true EP1436437B1 (fr) 2006-09-20

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EP (1) EP1436437B1 (fr)
JP (1) JP4101758B2 (fr)
CN (1) CN100513604C (fr)
AU (1) AU2002210901A1 (fr)
DE (1) DE60123296T2 (fr)
WO (1) WO2003035918A2 (fr)

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CN100455686C (zh) * 2006-12-29 2009-01-28 江苏大学 一种铜锌铝形状记忆合金耐磨材料及其制备方法
CN100529147C (zh) * 2007-10-24 2009-08-19 江阴鑫裕装潢材料有限公司 热型连铸获得的铜基形状记忆合金的超弹记忆热处理方法
CN101886187B (zh) * 2010-07-14 2011-11-09 南京信息工程大学 一种形状记忆铜合金及其制备方法
CN104233134A (zh) * 2013-06-14 2014-12-24 镇江忆诺唯记忆合金有限公司 提高铜锌铝记忆合金在碱性下滚动磨损性能的热处理方法
CN104561866B (zh) * 2015-02-04 2016-08-17 九江学院 多孔铜基形状记忆合金的等径角挤扭法制备工艺
CN108717025A (zh) * 2018-04-19 2018-10-30 电子科技大学 一种双程形状记忆合金热-机械功能疲劳特性测试装置
CN111304487B (zh) * 2020-03-24 2021-05-25 安新县华昌合金厂 一种铜基形状记忆合金及其制备方法和应用
CN111876631A (zh) * 2020-08-04 2020-11-03 厦门大学深圳研究院 一种铜锌铝基单晶合金及其制备方法

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BE758862A (fr) * 1969-11-12 1971-04-16 Fulmer Res Inst Ltd Perfectionnements relatifs au traitement d'alliages
GB1593499A (en) * 1976-03-18 1981-07-15 Raychem Corp Copper aluminium zinc alloy
NL7714494A (nl) * 1977-12-28 1979-07-02 Leuven Res & Dev Vzw Werkwijze voor het maken van vaste lichamen uit koper-zinkaluminiumlegeringen.
EP0043388A1 (fr) * 1980-07-04 1982-01-13 BBC Aktiengesellschaft Brown, Boveri & Cie. Alliage-mémoire à base de cuivre, de zinc et d'aluminium et procédé pour sa fabrication

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DE60123296T2 (de) 2007-06-06
EP1436437A2 (fr) 2004-07-14
CN100513604C (zh) 2009-07-15
JP4101758B2 (ja) 2008-06-18
WO2003035918A3 (fr) 2003-11-13
WO2003035918A2 (fr) 2003-05-01
DE60123296D1 (de) 2006-11-02
AU2002210901A1 (en) 2003-05-06
CN1547619A (zh) 2004-11-17
JP2005506450A (ja) 2005-03-03

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