磁场作用下Zn-Bi难混溶合金凝固组织演变规律的研究
发布时间：2019-06-20 16:02
【摘要】：难混溶合金是一种具有广泛工业应用前景的合金,但由于其独特的凝固特性,在常规凝固条件下,极易形成严重的比重偏析,导致其优异的性能无法充分发挥。近年来,随着超导技术和Bitter磁体技术的发展,实现了10-30 T量级的恒定、长时的强磁场。研究表明,其极强的洛伦兹力、磁场力、磁场能量效应对金属的凝固过程有着深远的影响,如合金相取向、晶粒迁移、枝晶细化等,显示其与常规凝固截然不同的规律和机制,将超强磁场应用于难混溶合金的凝固,以期望解决其比重偏析严重的问题,至今研究尚不深入。因此,开展磁场下难混溶合金凝固研究的意义非常重大。本文以Zn-Bi难混溶合金为研究对象,对0-30 T磁场下的难混溶合金的凝固行为开展了深入研究,并尝试探索常规重力和常规冷却条件下均质难混溶合金的制备途径。获得如下研究成果:研究了0-30 T纵向强磁场对成分处于难混溶区内的Zn-Bi合金凝固过程中第二相液滴偏析行为的影响规律。发现施加强静磁场可以显著抑制第二相Bi液滴的Stokes沉降运动和Marangoni运动,但高达29 T的强静磁场仍无法完全消除Spinodal分解造成的成分偏析。强静磁场对Zn-Bi合金中Bi液滴的形核与长大过程影响显著:磁场大于17.4 T时,Bi液滴以纯扩散方式长大;小于17.4T时,则以碰撞、凝并方式长大。研究了0-30 T纵向强磁场下冷却速度对Zn-6wt.%Bi难混溶合金凝固组织形貌的影响规律。结果表明,淬火冷却的Zn-6wt.%Bi难混溶合金的表层等轴晶中形成了一种链状组织;随炉冷却则形成了一种Bi包围Zn相的壳型凝固组织,并基于热电磁流理论探讨了壳型组织的形成机制。研究了横/纵向磁场诱导的热电磁力对合金凝固组织中第二相分布的影响规律。结果表明,1 T量级的横/纵向磁场在熔体中产生了显著的热电磁力,并形成了宏观的热电磁流动,显著改变了Bi液滴在空间的分布规律。针对采用29 T强静磁场和淬火冷却条件仍无法抑制具有强烈液液分离倾向的难混溶合金的Stokes沉降和Marangoni凝并导致的宏观偏析问题,提出了强磁场复合交变电流调控难混溶合金凝固组织的新方法。结果表明,当磁感应强度为10 T、电磁体积力为5×105 N/m~3、交变电流频率为50 Hz时,Zn-10wt.%Bi和Zn-20wt.%Bi合金凝固组织中Bi颗粒的粒径最小且最弥散,获得了几乎均匀的凝固组织。过低或过高的交变电流频率都会显著促进Bi液滴的碰撞和凝并,加重合金的偏析。由于在研究强静磁场对成分处于非难混溶区内的合金凝固影响的过程中发现,纵向强磁场对Zn-84~97.3wt.%Bi合金凝固组织的取向具有显著的影响,对比研究了磁场下Zn-95wt.%Bi合金和具有偏晶特性的Bi-Mn合金组织中析出相的取向机制。发现Zn-95wt.%Bi合金在0 T和6 T条件下其凝固组织显示出共同的磁各向同性,6 T条件下的凝固组织在平行于磁场方向上表现出最小的抗磁化强度特征;在2 T和4 T条件下则显示出共同的磁各向异性。在30 T和60℃/min的冷却条件下,Bi-Mn合金凝固组织中的α-BiMn的取向与磁场方向平行;在30 T和5℃/min的冷却速度时,则是一种呈多层分布的组织。本文对磁场作用下不同成分的Zn-Bi难混溶合金凝固过程的系统研究,丰富了磁场下难混溶合金的凝固理论,对均质的难混溶合金的制备具有重要的学术指导价值和工程意义。
[Abstract]:It is a kind of alloy with wide industrial application prospect, but due to its unique solidification characteristics, it is very easy to form serious specific gravity segregation under the condition of normal solidification, which leads to its excellent performance. In recent years, with the development of the superconducting technology and the Bitter magnet technology, a constant and long-term strong magnetic field of the order of 10-30T is realized. The research shows that the strong Lorentz force, the magnetic field force and the magnetic field energy effect have a far-reaching influence on the solidification process of the metal, such as the orientation of the alloy, the grain migration, the dendrite refinement and the like, and shows the rule and the mechanism which are completely different from the conventional solidification, The super-strong magnetic field is applied to the solidification of the immiscible alloy, so as to solve the problem that the specific gravity segregation is serious, and the research is not yet in-depth. Therefore, it is very important to carry out the research on the solidification of the immiscible alloy under the magnetic field. In this paper, the study of the solidification behavior of the immiscible alloy under the 0-30T magnetic field is carried out by taking the Zn-Bi difficult-to-heat transfer alloy as the research object, and the preparation method of the immiscible alloy under the conventional gravity and the conventional cooling condition is also tried. The effect of 0-30T longitudinal strong magnetic field on the segregation behavior of the second phase in the solidification process of Zn-Bi alloy is studied. It is found that the static magnetic field can significantly inhibit the Stokes settlement movement and the Marangoni motion of the second phase Bi droplets, but the strong static magnetic field up to 29T still cannot completely eliminate the component segregation caused by the Spinoidal decomposition. The effect of the strong static magnetic field on the nucleation and growth of Bi droplets in the Zn-Bi alloy is significant: when the magnetic field is greater than 17.4 T, the Bi droplets grow up in pure diffusion mode; when the magnetic field is less than 17.4 T, the Bi droplets grow up in a collision, coagulation and manner. The influence of the cooling rate of 0-30T in the longitudinal high magnetic field on the solidification structure of the hard-immiscible alloy with Zn-6wt.% Bi was studied. The results show that a chain-like structure is formed in the surface of the surface of the hard-cooled Zn-6 wt.% Bi-immiscible alloy, and a shell-type solidification structure surrounding the Zn phase is formed with the cooling of the furnace, and the formation mechanism of the shell-type tissue is discussed based on the theory of the heat-electromagnetic flow. The influence of the thermal electromagnetic force induced by the transverse/ longitudinal magnetic field on the second phase distribution in the solidification structure of the alloy is studied. The results show that the transverse/ longitudinal magnetic field on the order of 1 T has a significant thermal electromagnetic force in the melt, and a macroscopic thermal electromagnetic flow is formed, which significantly changes the distribution of Bi droplets in the space. A new method for controlling the solidification structure of the immiscible alloy with strong magnetic field compound alternating current is proposed for the problems of Stokes settlement and Marangoni's setting and the macro-segregation of the immiscible alloy with strong liquid-liquid separation tendency, which are still not restrained by the 29T strong static magnetic field and the quenching cooling condition. The results show that when the magnetic induction intensity is 10T, the electromagnetic volume is 5-105N/ m ~ 3, the frequency of the alternating current is 50 Hz, the particle size of Bi particles in the solidification structure of Zn-10 wt.% Bi and Zn-20wt.% Bi alloy is the smallest and the most diffuse, and the almost uniform solidification structure is obtained. The low or too high alternating current frequency can significantly promote the collision and coagulation of the Bi droplets and increase the segregation of the alloy. It is found that the orientation of the solidification structure of Zn-84-97.3 wt.% Bi alloy has a significant influence on the orientation of the solidification structure of Zn-84-97.3 wt.% Bi alloy during the study of the influence of the static magnetic field on the solidification of the alloy in the immiscible region. In this paper, the orientation mechanism of precipitation phase of Zn-95 wt.% Bi alloy and Bi-Mn alloy was studied. It is found that Zn-95 wt.% Bi alloy exhibits common magnetic isotropy under the condition of 0 T and 6 T, and the solidification structure under the condition of 6T shows the minimum anti-magnetization characteristic in the direction parallel to the magnetic field, and the common magnetic anisotropy is displayed under the condition of 2T and 4T. In the cooling condition of 30 T and 60 鈩，
本文编号：2503348
[Abstract]:It is a kind of alloy with wide industrial application prospect, but due to its unique solidification characteristics, it is very easy to form serious specific gravity segregation under the condition of normal solidification, which leads to its excellent performance. In recent years, with the development of the superconducting technology and the Bitter magnet technology, a constant and long-term strong magnetic field of the order of 10-30T is realized. The research shows that the strong Lorentz force, the magnetic field force and the magnetic field energy effect have a far-reaching influence on the solidification process of the metal, such as the orientation of the alloy, the grain migration, the dendrite refinement and the like, and shows the rule and the mechanism which are completely different from the conventional solidification, The super-strong magnetic field is applied to the solidification of the immiscible alloy, so as to solve the problem that the specific gravity segregation is serious, and the research is not yet in-depth. Therefore, it is very important to carry out the research on the solidification of the immiscible alloy under the magnetic field. In this paper, the study of the solidification behavior of the immiscible alloy under the 0-30T magnetic field is carried out by taking the Zn-Bi difficult-to-heat transfer alloy as the research object, and the preparation method of the immiscible alloy under the conventional gravity and the conventional cooling condition is also tried. The effect of 0-30T longitudinal strong magnetic field on the segregation behavior of the second phase in the solidification process of Zn-Bi alloy is studied. It is found that the static magnetic field can significantly inhibit the Stokes settlement movement and the Marangoni motion of the second phase Bi droplets, but the strong static magnetic field up to 29T still cannot completely eliminate the component segregation caused by the Spinoidal decomposition. The effect of the strong static magnetic field on the nucleation and growth of Bi droplets in the Zn-Bi alloy is significant: when the magnetic field is greater than 17.4 T, the Bi droplets grow up in pure diffusion mode; when the magnetic field is less than 17.4 T, the Bi droplets grow up in a collision, coagulation and manner. The influence of the cooling rate of 0-30T in the longitudinal high magnetic field on the solidification structure of the hard-immiscible alloy with Zn-6wt.% Bi was studied. The results show that a chain-like structure is formed in the surface of the surface of the hard-cooled Zn-6 wt.% Bi-immiscible alloy, and a shell-type solidification structure surrounding the Zn phase is formed with the cooling of the furnace, and the formation mechanism of the shell-type tissue is discussed based on the theory of the heat-electromagnetic flow. The influence of the thermal electromagnetic force induced by the transverse/ longitudinal magnetic field on the second phase distribution in the solidification structure of the alloy is studied. The results show that the transverse/ longitudinal magnetic field on the order of 1 T has a significant thermal electromagnetic force in the melt, and a macroscopic thermal electromagnetic flow is formed, which significantly changes the distribution of Bi droplets in the space. A new method for controlling the solidification structure of the immiscible alloy with strong magnetic field compound alternating current is proposed for the problems of Stokes settlement and Marangoni's setting and the macro-segregation of the immiscible alloy with strong liquid-liquid separation tendency, which are still not restrained by the 29T strong static magnetic field and the quenching cooling condition. The results show that when the magnetic induction intensity is 10T, the electromagnetic volume is 5-105N/ m ~ 3, the frequency of the alternating current is 50 Hz, the particle size of Bi particles in the solidification structure of Zn-10 wt.% Bi and Zn-20wt.% Bi alloy is the smallest and the most diffuse, and the almost uniform solidification structure is obtained. The low or too high alternating current frequency can significantly promote the collision and coagulation of the Bi droplets and increase the segregation of the alloy. It is found that the orientation of the solidification structure of Zn-84-97.3 wt.% Bi alloy has a significant influence on the orientation of the solidification structure of Zn-84-97.3 wt.% Bi alloy during the study of the influence of the static magnetic field on the solidification of the alloy in the immiscible region. In this paper, the orientation mechanism of precipitation phase of Zn-95 wt.% Bi alloy and Bi-Mn alloy was studied. It is found that Zn-95 wt.% Bi alloy exhibits common magnetic isotropy under the condition of 0 T and 6 T, and the solidification structure under the condition of 6T shows the minimum anti-magnetization characteristic in the direction parallel to the magnetic field, and the common magnetic anisotropy is displayed under the condition of 2T and 4T. In the cooling condition of 30 T and 60 鈩，
本文编号：2503348
本文链接：https://www.wllwen.com/kejilunwen/jiagonggongyi/2503348.html
