【作者】 王丽红；

【导师】 满蛟；

【作者基本信息】 新疆大学 ， 工程力学， 2023， 硕士

【摘要】 形状记忆合金及其相关的热弹性马氏体相变多年来一直是广泛研究的主题。形状记忆合金在实践中应用在航空航天、生物医学和日常生活的各个方面。通过外部加载改变形状记忆合金性能的这种工艺对增大形状记忆合金的使用范围至关重要。经过探究可得在外加载荷的作用下,热弹性马氏体的正相变以及逆相变会产生相当复杂的介微观的组织变化过程。对于目前的实验手段来说,对这种相对复杂的微观组织进行准确的实验探究和观察预测是相当困难的。从相场模拟的角度来说,材料领域已经将相场模拟用作一种有效的微观组织的观测和研究手段。然而,目前相场领域对马氏体相变及逆相变的研究大多停留在马氏体和奥氏体的微观演化、马氏体的自协调效应、母相转化为马氏体相过程中的多变体的择优取向和相关的特定现象等。但是对于外加拉伸和压缩载荷下马氏体的正相变和逆相变的研究较少。利用相场方法建立相场模型对外加载荷下的马氏体正逆相变的微观组织演化进行研究可以弥补实验和理论的不足,有助于研究者在热力学的角度加深对相变行为的认识,并且对微观演化加深理解。本文建立了一种新的马氏体逆相变的相场模型,该模型考虑了正相变过程储存的应变能对其逆相变的影响。利用建立的相场模型研究了单轴加载下的马氏体正-逆相变,在模拟角度揭示并证明了外加载荷可以释放弹性应变能的这种机制,同时研究了外加载荷诱导产生的马氏体稳定现象,揭示了外加载荷条件下产生的马氏体变体择优取向的规律。并且通过相场模型,探讨了双轴加载对马氏体相变的作用。主要研究结论如下:(1)本文基于Ginzburg-Landau相变理论建立了热弹性马氏体正-逆相变的相场模型。实现了对热弹性马氏体相变和逆相变的微观相变行为预测,并通过实验对相场模型进行了验证,证实了模型的可行性。(2)通过建立的相场模型,计算得到了在外加载荷的作用下,马氏体相变过程中的弹性应变能呈现减小的趋势,即外加载荷对马氏体相变过程中的弹性应变能具有释放作用。(3)马氏体相变产生的弹性应变能是马氏体相变的阻力,是其逆相变的驱动力。在马氏体相变过程中,外加单轴和双轴载荷均会对马氏体相变起到促进作用。(4)在马氏体的逆相变过程中,由于外加单轴载荷降低了马氏体所贮存的应变能,因而降低了逆相变过程的驱动力,抑制了马氏体逆相变的转化。(5)外加单轴载荷会使逆相变起始温度As升高,诱导马氏体产生稳定性。这是由于外加载荷对马氏体相变中储存的弹性应变能具有释放作用,使马氏体发生逆相变的驱动力减低,发生逆相变困难,增加了马氏体在高温相的稳定性。(6)外加单轴载荷和外加双轴载荷均会使马氏体变体产生择优取向现象,不同的加载方式导致马氏体变体的择优取向方向也不尽相同。经过研究,单轴拉伸载荷、单轴压缩载荷和双轴拉伸载荷会诱导马氏体变体向着变体2的方向择优取向,双轴压缩载荷会诱导马氏体变体向着变体3的方向择优取向。更多还原

【Abstract】 The shape memory alloy and its associated thermoelastic martensitic transformation have been the subject of extensive research for many years.Shape memory alloys are used in the practice of aerospace,biomedical and daily life.The process of loading the properties of the shape memory alloy by external loading is critical to the use of the shape memory alloy.Under the effect of the exploration of the load,the positive phase transition of the thermoelastic martensitic transformation and the reverse martensitic transformation can produce quite complex microstructure changes.It is quite difficult for the current experimental methods to conduct accurate experimental exploration and observation of this relatively complex microstructure.From the point of view of phase simulation,the field of materials has been used as an effective observation and research method of the microscopic organization.However,the current phase of the martensitic transformation and reverse martensitic transformation is mostly in the martensitic and austenitic microevolution,the selfcoordination effect of the martensitic transformation,the transformation of the parent phase into the selection of the variable in the process of the horse,and the specific phenomena associated with the martensitic transformation process,etc.However,there is less research on the martensitic transformation and reverse martensitic transformation of the additional stretch and compression load.The study of the evolution of the martensitic transformation and the reverse martensitic transformation change of the phase field model of the phase field model can be used to make up for the deficiency of the experiment and theory.The phase field method helps the researchers to deepen their understanding of phase transition behavior in thermodynamic terms,and deepen understanding of microevolution.In this paper a new phase field model of the reverse martensitic transformation is established.This model considers the effect of the strain of the reverse martensitic transformation process.This model takes into consideration the effect of elastic strain on the This model takes into consideration the effect of elastic strain on the reverse martensitic transformation of the martensitic transformation process of the positive phase transition process.Using the set of phase field model,the martensitic transformation and reverse martensitic transformation were studied.In the simulation Angle,this mechanism is revealed and the extra load can release elastic strain energy.At the same time,the stability of the martensitic transformation is studied by the plus load induction,and the law of the selection of the horse’s body variation under the additional load condition is revealed.In this paper,the function of the biaxial load on the phase transition of the martensitic phase is discussed.The main conclusions are as follows:(1)Based on Ginzburg-Landau phase transition theory,this paper establishes the phase field model of thermal elastic martensitic transformation and reverse martensitic transformation.This model is used to predict the microphase phase of the thermoelastic martensitic transformation and reverse martensitic transformation.The feasibility of the model is verified by experiment.(2)By the establishment of the phase field model,the elastic strain can be reduced by the effect of the outer loading load,which is the elastic strain that can be released in the process of the martensitic transformation.(3)The elastic strain is the resistance of the martensitic transformation,the driving force of its reverse martensitic transformation.In the process of the martensitic transformation,uniaxial load and biaxial load will promote the martensitic transformation.(4)In the process of the reverse martensitic transformation of the martensitic transformation,the force of the reverse martensitic transformation process is reduced by the addition of the uniaxial tensile load,which reduces the transformation of the reverse martensitic transformation.(5)Uniaxial load will increase the temperature As of the reverse martensitic transformation temperature and induce the stability of the martensitic.This is because the extra load has a release effect on the elastic strain stored in the martensitic transformation.This effect reduces the driving force of the reverse martensitic transformation and the reverse martensitic transformation is difficult.The stability of the martensitic transformation in high temperature phase.(6)uniaxial load and biaxial load will make the martensitic transformation variant produce the orientation phenomenon.Different loading methods cause different directions for the variant of the martensitic transformation.After study,the uniaxial tensile load,uniaxial compressive load and the biaxial tensile load will induce the variant of the martensitic transformation to be chosen in the direction of variant 2.The biaxial compressive load induces the variation of the martensitic transformation to be preferred in the direction of the variant 3.更多还原