共查询到19条相似文献,搜索用时 203 毫秒
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Ni52Mn24Ga24金属间化合物的单晶生长和磁性功能 总被引:3,自引:0,他引:3
研究了Ni52Mn24Ga24合金单晶在磁场作用下能产生的目前最大的磁致伸缩应变,发现了该材料的双向相变应变效应以及磁场对此的增强现象,在1.2T磁场的作用下,可逆的相变应变达4%以上,实现这一结果的关键条件是马氏体变体的择优取向。报道了获得马氏体变体的择优取向样品的单晶生长特性和后处理方法,根据前人报道的理论模型分析了实验结果,指出磁感生应变的物理机制是磁场提供的Zeeman能驱动变体间孪晶界的移动。 相似文献
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Ni_(52)Mn_(24)Ga_(24)金属间化合物的单晶生长和磁性功能 总被引:2,自引:0,他引:2
研究了 Ni52Mn24Ga24合金单晶在磁场作用下能产生的目前最大的磁致伸缩应变.发现了该材料的双向相变应变效应以及磁场对此的增强现象.在 1.2 T磁场的作用下,可逆的相变应变达 4%以上实现这一结果的关键条件是马氏体变体的择优取向报道了获得马氏体变体的择优取向样品的单晶生长特性和后处理方法根据前人报道的理论模型分析了实验结果,指出磁感生应变的物理机制是磁场提供的 Zeeman能驱动变体间孪晶界的移动 相似文献
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稳恒磁场在材料科学中的应用越来越受到关注。本文从稳恒磁场作用下生成的磁化力和洛伦兹力两个角度归纳了稳恒磁场对金属材料的固态相变和液态相变的影响。其中磁化力可以影响固态相变过程,形成取向,引起磁对流,进行磁性分离。而洛伦兹力可以抑制熔体的流动和波动,提高溶质离子在基体中的固溶度,另外,利用洛伦兹力还可以在电磁离心铸造中获得均匀的凝固组织。 相似文献
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稳恒磁场在材料科学中的应用越来越受到关注。本文从稳恒磁场作用下生成的磁化力和洛伦兹力两个角度归纳了稳恒磁场对金属材料的固态相变和液态相变的影响。其中磁化力可以影响固态相变过程,形成取向.引起磁对流,进行磁性分离。而洛伦兹力可以抑制熔体的流动和波动,提高溶质离子在基体中的固溶度,另外,利用洛伦兹力还可以在电磁离心铸造中获得均匀的凝固组织。 相似文献
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强磁场对Bi-Mn合金355℃包晶相变点的影响 总被引:2,自引:1,他引:2
根据物质在梯度磁场中的受力与其磁性相关的原理,提出了通过测定合金在磁场中的受力来了解其相变的方法.根据该方法,对Bi-Mn合金在不同磁场强度下包晶相变点进行了测定,并从热力学上分析了强磁场对相变点的影响.结果发现:随磁场强度的提高,合金的包晶相变点逐渐提高,在10 T磁场下,相变点提高20℃左右.同时,强磁场的施加促进了MnBi相的形态由块状向片状的转变. 相似文献
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证实了Ni53.2Mn22.6Ga24.2单晶发生的两步马氏体相变行为是完全热弹性的. 在磁场作用下, 该材料的马氏体相变和中间马氏体相变展现出相同的应变特征, 且具有磁控双向形状记忆效应. 磁场下应力--应变特性的测量结果表明, 磁场不但对压应力诱发马氏体相变过程中变体重取向所需应力的大小有影响, 而且使原来不可逆的形变成为可逆, 这种磁控超弹性特性预示了该合金用作磁控超弹性元器件材料的可能性. 相似文献
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铁磁性Heusler合金Ni2 MnGa是近年开发的磁控制功能材料 ,已发现该材料结合马氏体相变可以产生大磁致伸缩 (磁感生应变 )和磁控制形状记忆效应两种应用功能。用磁悬浮冷坩埚提拉设备沿 [0 0 1]方向生长了组分为Ni52 Mn2 4 Ga2 4 的单晶。室温时沿该单晶样品 [0 0 1]方向加磁场 ,在该方向获得了 - 0 6 %的大磁感生应变。当磁场方向垂直于 [0 0 1]方向时 ,样品在 [0 0 1]方向的磁感生应变值为 0 5 %。同时该单晶样品在室温附近还具有可由磁场增强和控制的双向形状记忆效应。无磁场作用时 ,降低温度 ,样品在发生马氏体相变时 ,在 [0 0 1]方向产生1 2 %的收缩形变。随后升高温度 ,反马氏体相变时样品以同样的应变量膨胀 ,恢复到原来的形状 ,显示了特有的无需外应力协助的自发的双向形状记忆效应。其温度滞后只有 10℃。如果在样品的 [0 0 1]方向加一个偏磁场 ,其形状记忆的应变量随磁场的增强而增大。在磁场为 1 2T时可达 4%。而当磁场转向 [10 0 ]方向时 ,形状记忆的应变可以改变符号。本文指出产生大磁感生应变和磁增强双向形状记忆效应的关键是马氏体变体的择优取向。 相似文献
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V.A. L’vov N. Glavatska I. Aaltio O. Söderberg I. Glavatskyy S.-P. Hannula 《Acta Materialia》2009,57(18):5605-5612
The functional properties of a ferromagnetic shape memory alloy, which undergoes martensitic transformation of a cubic-tetragonal type, have been analyzed using the Landau theory of phase transitions. A key role of the temperature dependency of the crystal lattice parameters in the formation of the elastic and magnetic properties of the martensitic phase has been determined. To this end the temperature dependencies of the shear elastic moduli and magnetic anisotropy energy densities (MAED) of two quasi-stoichiometric Ni–Mn–Ga alloys have been computed from the experimental temperature dependencies of their lattice parameters. It turned out that the differences in the temperature dependencies of the lattice parameters of these alloys gave rise to drastic differences in their shear moduli and MAED as a function of temperature. The possibility of the spontaneous reorientation of the magnetization vector on cooling of the alloy and a right-angle realignment of this vector by a low magnetic field have been predicted. 相似文献
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SUN Enxi Dalian Railway College Dalian ChinaYANG Dazhi Dalian University of Technology Dalian ChinaXU Zuyao 《金属学报(英文版)》1991,4(1):8-12
The pulsed magnetic field induced martensitic transformation with isothermal and athermal kinetics in Fe-2Ni-4Mn(wt-%)alloy has been studied by means of magnetization measurements,optical microscopy and thermodymical analyses.It is shown that there exits a critical magnetic intensity for induing martensitic transformation at a given temperature above Ms.The critical magnetic field increases linearly with increasing ΔT= T-M_S.The magnetic field strongly promotes the athermal martensitic transforamtion and restrains the isothermal one.The entropy change ΔS for athermal transformation at Ms is 4.13 J/mol· K.The effect of magnetic field on martensitic transformation in Fe-21Ni-4Mn alloy is main- ly due to Zeeman effect.Lath,plate and butterfly martensities were observed under magnetic field. 相似文献
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采用多种测量手段,对制备出的转变温度在室温以上的Ni46Mn35Ga19单晶的物性进行表征。电阻和交流磁化率结果表明,该材料的磁转变和马氏体相变是同时发生的。定温磁化强度测量得出材料磁熵变的增长速率高达9.0J/kg·K·T,在1274kA/m(1.6T)的磁场下,磁熵变达13.8J/kg·K。此外,应变测量表明,伴随该磁熵变,材料展现出应变量分别高达–0.89%和–1.90%的自发和磁控双向形状记忆效应。 相似文献
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Ti49.4Ni50.6超弹性弹簧的相变和形变特性 总被引:13,自引:2,他引:13
用示差扫描量热仪、拉伸实验和应力-应变循环实验系统研究了退火温度、变形温度以及热循环和室温应力-应变循环对Ti49.4Ni50.6超弹性(SE)弹簧的相变和形变特性的影响。冷加工加中温退火态Ti49.4Ni50.6合金冷却→←加热时的相变类型为母相B2→←R相→←马氏体B19′。随退火温度升高,马氏体转变温度升高,R相转变温度降低。623-773K退火态Ti49.4Ni50.6弹簧室温下可获得SE特性,随变形温度升高,SE弹簧剐度增加;当退火温度超过823K后,SE持性变差。热循环时SE弹簧的切变量取值越小,其应变恢复率越高。预循环训练可增强SE的稳定性。 相似文献
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R.Y. Umetsu K. ItoW. Ito K. Koyama T. KanomataK. Ishida R. Kainuma 《Journal of Alloys and Compounds》2011,509(5):1389-1393
High-field magnetic measurements were carried out in order to investigate behaviors of field-induced reverse martensitic transformation and kinetic arrest of NiCoMnSn metamagnetic shape memory alloy. In the thermomagnetization curves, it was confirmed that the reverse martensitic transformation temperature decreases 67 K by applying magnetic field of 5 T, while in the magnetic field cooling process under 5 T, martensitic transformation does not occur down to low temperatures. Equilibrium magnetic field, defined from the critical magnetic fields of the metamagnetic evidence in the magnetization curves, exhibits almost constant below about 100 K, suggesting that the entropy change becomes zero, which is considered to cause kinetic arrest behavior. 相似文献
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《Acta Materialia》2002,50(3):467-474
A modified Landau–Ginzburg theory for martensitic transformations is suggested. An accommodation strain energy in parent phase is added into the free energy of the system besides the Landau free energy and gradient energy which have been generally considered. Both the equilibrium state and the dynamic process of martensitic transformations are investigated by solving the equation of motion numerically. Two important features of martensitic transformations, i.e., transformational hysteresis and athermal transformation, can be displayed by the modified model. The results of numerical study of the model agree with experiments well, including surface martensite, thermoelastic and nonthermoelastic martensite formations, autocatalysis and burst transformation. 相似文献