含应力产生缺陷的预相变材料对外部激励的响应：超弹性、超磁致伸缩、因瓦和埃林瓦效应
Responses of Pre-transitional Materials with Stress-Generating Defects to External Stimuli: Superelasticity, Supermagnetostriction, Invar and Elinvar Effects
摘要：
我们考虑了具有静态应力产生缺陷、位错和相干纳米沉淀物的预过渡材料的一般情况，在接近但高于马氏体相变起始温度的温度下，Ms.使用相场微弹性理论和3D模拟，我们证明了由这些缺陷产生的局部应力产生处于预过渡状态的平衡纳米尺寸马氏体胚（ME），这些胚是马氏体的取向变体。这是一种新的平衡类型：ME和母相之间的热弹性平衡，其中ME的总体积和它们的尺寸是平衡的内部热力学参数。这种热弹性平衡只存在于产生应力的缺陷中。将预过渡状态冷却到Ms或施加外部刺激、应力或磁场，导致由ME的可逆无滞后生长提供的热弹性平衡的偏移，这导致巨大的ME产生的宏观应变。特别是，这种效应可以与居里点以上的一些铁电体中观察到的扩散相变。结果表明，ME产生的应变是巨大的，并描述了一个超弹性，如果所施加的场是应力。它描述了一个超磁致伸缩，如果马氏体（或奥氏体）是铁磁性和所施加的领域是一个磁场。一般来说，如果母相和马氏体相具有不同的铁性，则具有缺陷的材料可以是具有巨多铁性响应的多铁性材料。最后，ME产生的应变可以解释或至少有助于通常在过渡前奥氏体中观察到的因瓦和埃林瓦效应。只有当缺陷与微电子之间的相互作用是无限程时，热弹性平衡和所有这些效应才存在。
英文摘要：
We considered a generic case of pre-transitional materials with static stress-generating defects, dislocations and coherent nano-precipitates, at temperatures close but above the starting temperature of martensitic transformation, Ms. Using the Phase Field Microelasticity theory and 3D simulation, we demonstrated that the local stress generated by these defects produces equilibrium nano-size martensitic embryos (MEs) in pre-transitional state, these embryos being orientation variants of martensite. This is a new type of equilibrium: the thermoelastic equilibrium between the MEs and parent phase in which the total volume of MEs and their size are equilibrium internal thermodynamic parameters. This thermoelastic equilibrium exists only in presence of the stress-generating defects. Cooling the pre-transitional state towards Ms or applying the external stimuli, stress or magnetic field, results in a shift of the thermoelastic equilibrium provided by a reversible anhysteretic growth of MEs that results in a giant ME-generated macroscopic strain. In particular, this effect can be associated with the diffuse phase transformations observed in some ferroelectrics above the Curie point. It is shown that the ME-generated strain is giant and describes a superelasticity if the applied field is stress. It describes a super magnetostriction if the martensite (or austenite) are ferromagnetic and the applied field is a magnetic field. In general, the material with defects can be a multiferroic with a giant multiferroic response if the parent and martensitic phase have different ferroic properties. Finally the ME-generated strain may explain or, at least, contribute to the Invar and Elinvar effects that are typically observed in pre-transitional austenite. The thermoelastic equilibrium and all these effects exist only if the interaction between the defects and MEs is infinite-range.
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