阐明了磁声波的生成原理，对磁声波的传播特性、衰减机理以及磁声波的反射和透射做了深入系统的探讨和分析。研究表明，磁声波的传播速度、反射率和透射率和通常的纵波不同，不仅和媒质的性质有关，而且是所施加的静磁场磁感应强度的函数；磁声波的衰减主要是由于Joule耗散所gI起的。研究成果对促进磁声波在材料领域的应用是大有裨益的。

Compression waves propagating through molten metals are contributed to degassing, accelerating reaction rate, removing exclusions from molten metals and refining solidification structures during metallurgical processing of ma-terials. In the present study, two electromagnetic methods are proposed to generate intense compression waves directly in liquid metals. One is the simultaneous imposition of a high frequency electrical current field and a static magnetic field; the other is that of a high frequency magnetic field and a static magnetic field. A mathematical model based on compressible fluid dynamics and electromagnetic fields theory has been developed to derive pressure distri-butions of the generated waves in a metal. It shows that the intensity of compression waves is proportional to that of the high frequency electromagnetic force. And the frequency is the same as that of the imposed electromagnetic force. On the basis of theoretical analyses, pressure change in liquid gallium was examined by a pressure transducer under various conditions. The observed results approximately agreed with the predictions derived from the theoretical analyses and calculations. Moreover, the effect of the generated waves on improvement of solidification structures was also examined. It shows that the generated compression waves can refine solidification structures when they were applied to solidification process of Sn-Pb alloy. This study indicates a new method to generate compression waves by imposing high frequency electromagnetic force locally on molten metals and this kind of compression waves can probably overcome the difficulties when waves are excited by mechanical vibration in high temperature environments.

The effects of strong magnetic fields on solidified structures of metals with different magnetic permeabilities are studied theoretically and experimentally. A mathematical model is established to investigate the effects of strong magnetic fields on the nucleus formation during the solidification processing of metals. Based on the theoretical analyses, the experiments are carried out in which strong magnetic fields are imposed on metals with different magnetic permeabilities during their solidification processing in Ar atmosphere. Then the macrostructures of samples are examined and the influences of magnetic susceptibilities of metals, intensity and gradient of magnetic fields are analyzed in details. It shows that the mechanisms of magnetic energy and magnetization forces to solidified structures are different, the former can affect the grain sizes of metals and the latter also can make the crystals orientate to some specific crystallographic direction.

A new generating method of compression waves in a liquid metal has been proposed in which a static magnetic field and an alteLJating current are simultaneously imposed. The theoretical expressions of intensities and distributions of pressure and velocity accompanied with the compression waves have been derived. The pressure change in liquid gallium excited by the method proposed here was measured under different intensities of the magnetic field and the alternating cut,eat. The measured pressures approximately agreed with the theoretical evaluation The structure of a Sn-Pb alloy that was solidified under the imposition of the compression waves, was completely refined.

In order to generate intense compression waves in a molten metal under non-contact operation, a new method has been proposed where a high static magnetic field and a high frequency one are simultaneously imposed on a molten metal. A mathematical model based on the compressible fluid dynamics and the electromagnetic field theory has been developed to derive the pressure distribution in a metal. The intensity of compression waves is indicated as a function of physical properties of a metal and operating conditions. Furthermore, the pressure oscillation caused by compression waves was measured and compared with the theoretical prediction derived by the mathematical model.

提出了运用强磁场和交流电流的共同作用直接在金属液中产生声波（磁声波）的新方法，并研究了所生成的磁声波在细化合金凝固组织晶粒的效果。该方法可以从根本上解决机械声波无法在高温生产领域应用的难题。理论解析表明，运用交变电磁力在液体金属内生成的磁声波的强度和所施加的静磁场的磁感应强度和交流电流的电流密度的乘积成正比；电磁力的频率越大，生成的磁声波越接近于由机械振动产生的声波。实验中测定的磁声波压力和理论解析结果基本一致。这种方法产生的磁声波具有促进金属凝固组织晶粒细化的作用。

为解决由机械振动产生的超声波无法在高温环境中成功应用的难题，提出了利用静磁场和交流电流、静磁场和交流磁场的相互作用分别在金属液内直接生成高强度电磁超声波的方法，运用超声波压力传感器对用这两种方法在金属液内生成的电磁超声波的强度进行了测量。研究表明:电磁超声波的强度与所施加的高频电磁力的强度成正比，频率与电磁力的频率相同；实验结果和理论解析结果基本一致；利用高频电磁力的局部作用在金属液全场范围内生成的电磁超声波可以在金属精炼及凝固过程中获得广泛应用。

在材料电磁过程研究中，静磁场尤其是强磁场材料科学是当今世界的研究热点。本文从静磁场作用下生成的洛仑兹力和磁化力两个角度系统地归纳总结了静磁场技术在材料生产领域的应用原理和实践。对静磁场下的洛仑兹力，主要介绍了流体流动、波动和对流控制、电磁振动及电磁超声波等方面的研究现状；对强磁场下的磁化力，主要介绍了其在相变、结晶配向、磁悬浮、磁对流等方面的研究进展。最后对强磁场材料科学的研究趋势和发展前景做了展望。

研究了静磁场和梯度磁场的强度和方向对A1-15.7%Si合金宏观和微观凝固组织的影响。结果表明，在不同的磁场条件下，从过共晶合金中析出的初晶硅粒的分布状况和共晶硅的形态和密度有显著不同。通过改变磁感应强度和磁场梯度的大小和方向可有效控制初晶硅的分布；合理控制强磁场的操作参数可达到细化铝硅共晶体的目的。强磁场的磁化力和洛伦兹力通过控制初晶硅颗粒迁移行为来改变其在合金基体中的分布状态，通过影响凝固过程中的对流现象改变合金的凝固组织。