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.