Fe掺杂Mn-Cu系的恒模量和广义类橡皮行为的研究

发布时间：2018-06-18 12:38

本文选题：Fe掺杂Mn-Cu合金 + 动态力学分析　；参考：《上海交通大学》2015年博士论文

【摘要】：材料的异常性能总是会引起研究者的广泛兴趣,它们在各个领域的特殊场合下都存在着潜在的应用。恒模量和类橡皮行为是材料的两种异常性能。100年前,Guillaume发现并研发了两种性能不随温度改变的合金——恒膨胀Invar合金以及恒模量Elinvar合金,为此他于1920年获得了诺贝尔物理学奖。Weiss建立了基于两种磁性状态共存的物理学框架来解释Invar效应。随后基于第一性原理的计算揭示了磁性态与晶格常数及模量的关联,但是至今对于模量反常的物理图像在介观尺度内仍然不清楚。本文的目的就是通过实验与相场模拟来揭示模量反常的起因。类橡皮行为的机制主要是“对称性适应短程序”理论(SC-SRO),其主要适用于有序合金,但对于无序合金的解释略显牵强。为此,本文将对无序合金是否存在类橡皮行为和它的起因进行相场动力学模拟研究。两种异常性能研究主要的结果描述如下：1.对于三种Fe掺杂Mn-Cu合金进行的动态力学分析(DMA)显示：低浓度掺杂合金(Mn80Fe15Cu5)与高浓度掺杂合金Mn80Fe15Cu5在-150℃至150℃均呈现正常的模量温度效应,即随温度降低模量升高,其中前者为单一或主导的同轴(Collinear)反铁磁结构,后者为单一或主导的非同轴(Non-collinear)反铁磁结构；而介于中间的掺杂合金(Mn70Fe25Cu5)在0℃至200℃之间呈现宽温区的反常模量温度效应,其为一定比例的同轴反铁磁结构与非同轴反铁磁结构的组合。针对后者的相场动力学模拟,提出了“动态反铁磁畴尺寸”效应(DAFDS),即高自旋同轴反铁磁畴尺寸随温度上升(下降)而缩小(增大),相应的低自旋非同轴畴界随温度上升(下降)而增大(缩小),由于高自旋同轴反铁磁结构具有较低的模量,由此导致了反常和连续的模量-温度效应。在上述模拟的基础上,进一步提出了宽温区模量反常的必要条件和充分条件：存在多种高自旋反铁磁畴变体是模量反常的必要条件,由掺杂引入导致的低自旋(非同轴)反铁磁畴界密度提高是模量反常的充分条件,由此很好地解释了掺杂Mn-Cu合金中出现的模量正常和反常现象。该效应首次在介观尺度清晰显示出高自旋畴长大和收缩的演化伴随模量反常的物理图像。2.通过相场动力学模拟的Fe掺杂Mn-Cu合金模量随温度的变化,由此显示出在单相奥氏体中无法得到宽温度区的恒模量效应,为此本文通过复合材料设计的思想,通过设计和优化热处理工艺,得到了Mn70Fe25Cu5合金中β、γ相的两相组织,由p相控制正常模量温度效应、而γ相控制反常模量温度效应,由此整体样品在-150℃至150℃的温度区间内模量随温度波动在2%范围内,体现为300K宽温区的Elinvar效应,其远高于目前在Mn-Cu系及Mn-Fe-Cu系合金所报道的0℃-40℃的Elinvar效应。3.使用相场动力学模拟研究了[100][110]和[111]三个不同方向加载下马氏体变体重排的动力学过程,结果表明,[100]方向加载去孪生(detwinning)为两个马氏体变体所需的临界应力最小,[110]方向加载去孪生为一个马氏体变体所需要的临界应力其次,而[111]方向加载为母相(类似于逆相变)所需的应力最大。当卸载时,三个方向的组织回到加载前自协调的三个马氏体。[100]和[110]方向的卸载导致的伪弹性来自于马氏体变体重排,这一机制不同于通常的应力诱发马氏体正逆相变机制。模拟结果也显示出不同方向应力加载条件下组织演化特征以及细微的界面迁移过程,即为一个加载-卸载伪弹性循环中微观组织所经历的演化路径,提出了导致伪弹性的马氏体变体重排机制,这一机制不同于通常的应力诱发马氏体正逆相变机制。4.类橡皮行为的模拟结果显示：回复驱动力来自于应力推动三个马氏体变体中某一变体消失后所积累的应变能；当长时间加载造成某一变体完全消失而在卸载需要重新形核时,这种情况将不利于类橡皮行为。上述机制均不需要满足SC-SRO条件,但与SC-SRO理论预测现象一致,故本文称上述在加载和卸载过程中某一马氏体变体收缩和回复的机制为类橡皮行为的本征机制。在本文的模拟中,类橡皮行为实质是具有应力时效下的马氏体变体重排的伪弹性。
[Abstract]:The abnormal properties of materials always arouse the wide interest of the researchers. They have potential applications in various special fields. Constant modulus and rubber like behavior are two kinds of abnormal properties of materials.100 years ago. Guillaume discovered and developed two kinds of alloys that do not change with temperature, constant expansion Invar alloy and constant Moduli Elinvar alloy, for which he won the Nobel prize in physics in 1920,.Weiss established a physical framework based on two kinds of magnetic states to explain the Invar effect. Then, based on the calculation of the first principle, the relation between the magnetic state and the lattice constant and modulus was revealed, but the physical image of the moduli was in the mesoscopic scale. The purpose of this article is not clear. The purpose of this paper is to reveal the cause of modulus abnormality through experiment and phase field simulation. The mechanism of rubber like behavior is mainly "symmetric adaptation short program" theory (SC-SRO), which is mainly applied to ordered alloys, but it is slightly far fetched for disordered alloys. The phase field dynamics simulation of rubber behavior and its origin is studied. The main results of two abnormal performance studies are described as follows: 1. the dynamic mechanical analysis (DMA) for three kinds of Fe doped Mn-Cu alloys shows that low concentration doped alloy (Mn80Fe15Cu5) and high concentration doped alloy Mn80Fe15Cu5 present normal modes at -150 C to 150 C The temperature effect, that is, the modulus increases with the temperature, the former is a single or dominant coaxial (Collinear) antiferromagnetic structure, and the latter is a single or dominant non coaxial (Non-collinear) antiferromagnetic structure; and the intermediate doped alloy (Mn70Fe25Cu5) shows the anomalous modulus temperature effect at a wide temperature zone between 0 and 200. A fixed proportion of the coaxial antiferromagnetic structure is combined with a non coaxial antiferromagnetic structure. According to the phase field simulation of the latter, the dynamic antiferromagnetic domain size effect (DAFDS) is proposed, that is, the size of the high spin coaxial antiferromagnetic domain is reduced with the temperature rise (decrease), and the corresponding low spin non coaxial domain boundaries increase with the temperature rise (drop). Due to the low modulus of the high spin coaxial antiferromagnetic structure, it leads to the anomalous and continuous modulus temperature effect. On the basis of the above simulation, the necessary conditions and sufficient conditions for the anomalous modulus of the modulus of the wide temperature zone are further proposed: the existence of a variety of high spin antiferromagnetic domain variants is a necessary condition for the modulus abnormality. The increase in the boundary density of the low spin (non coaxial) antiferromagnetic domain is a sufficient condition for the abnormal modulus of the moduli, which is a good explanation for the normal and anomalous phenomena of the modulus of the doped Mn-Cu alloy. This effect first clearly shows the evolution of the high spin domain and contraction in the mesoscopic scale, which is associated with the physical image of the abnormal modulus of the moduli,.2. pass. The modulus of Fe doped Mn-Cu alloy with the over phase field dynamics changes with the temperature, which shows that the constant modulus effect can not be obtained in the wide temperature zone in the single-phase austenite. Therefore, by designing and optimizing the heat treatment process, the two phase structure of beta and gamma phase in the Mn70Fe25Cu5 alloy is obtained by the idea of composite material design. The P phase is controlled by the phase field. The normal modulus temperature effect, while the gamma phase controls the abnormal modulus temperature effect, thus the modulus of the whole sample fluctuates in the range of 2% in the temperature range of -150 C to 150 C, which is reflected in the Elinvar effect of the 300K wide temperature zone, which is far higher than the phase field movement of the Elinvar effect.3. reported at the Mn-Cu and Mn-Fe-Cu alloys at 0 C -40 C. The dynamic process of martensitic rearrangement under three different directions of [100][110] and [111] is studied by mechanical simulation. The results show that the critical stress required for loading the two martensite variants in the [100] direction is the smallest, and the critical stress required by the [110] direction to be a martensitic variant is followed by the [110] direction, and [111] The maximum stress required to load the direction as the parent phase (similar to the reverse phase transition) is maximum. When unloading, the three directions of the tissues return to the three martensite.[100] and [110] direction before loading. The pseudoelasticity comes from the martensitic rearrangement. This mechanism is different from the normal stress induced martensitic transformation mechanism. It also shows the microstructure evolution characteristics and fine interface migration process under different direction stress loading conditions, that is, the evolution path of microstructures in a loading and unloading pseudo elastic cycle, and the martensitic variant rearrangement mechanism that leads to pseudoelasticity is proposed. This mechanism is different from the normal stress induced martensitic reverse phase change machine. The simulation results of.4. type rubber behavior show that the response driving force is derived from the strain energy accumulated after the stress pushes a certain variant of the three martensite variant. When a long time load causes a certain variant to disappear completely and when the unloading needs to be re nucleated, this situation will be unfavorable to the type of rubber like behavior. All of these mechanisms do not need to be full. SC-SRO condition is sufficient, but it is consistent with the prediction of SC-SRO theory. Therefore, this article calls the mechanism of the contraction and recovery of a martensitic variant in loading and unloading process as the intrinsic mechanism of rubber like behavior. In this simulation, the type of rubber behavior is essentially a pseudoelasticity of martensitic variant rearrangement under stress aging.
【学位授予单位】：上海交通大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TG145

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