The surface modification of magnesium alloys (AZ31 and AZ91HP) was studied by a high current pulsed elect ron beam( HCPEB) . The result s show that the cross2sectional microhardness of t reated samples increases not only in the heat affected zone ( HAZ) , but also beyond HAZ , reaching over 250μm. This is due to the action of quasi2static thermal st ress and the shock thermal st ress wave with materials , which result in it s fast deformation on the surface layer and so increases microhardness. For the AZ91HP alloy , a nearly complete dissolution of the inter2 metallic phase Mg17Al12 is observed , and a super2saturated solid solution forms on the re2melted surface , which is due to the solute t rapping effect during the fast solidification process. Measurement s on sliding wear show that wear resistance is improved by approximately 5. 6 and 2. 4 times for the AZ31 and AZ91HP respectively , as compared with as2received samples.

This paper reports an analysis of the microstructure and property modifications on a commercial Mg alloy AZ91HP treated by using High Current Pulsed Electron Beam (HCPEB). It is shown that, a thin layer consisting of nanograined MgO formed on the top surface after HCPEB (electron energy ∼30 keV, pulse duration 1 μs, energy density ∼3 J/cm2) treatment, below which is a melted layer with depth of about 8–10 μm. The heat affected zone (HAZ) underneath the melted layer and stress wave affected zone contains many stress induced deformation marks. Meantime, a nearly complete dissolution of the intermetallic phase Mg17Al12 in the melted layer is observed, leading to the formation of a supersaturated solid solution on the surface. This is due to the solute trapping effect occurred during the fast solidification process. As a result, the wear and corrosion resistance of the alloy were significantly improved as shown by sliding friction, wear and immersion tests.

The properties of boron carbide-lanthanum boride composite material prepared by hot pressed sintering method was tested, lanthanum boride as a sintering aid for boron carbide is investigated in this paper. The study shows: the hardness of boron carbide-lanthanum boride increases with the content of lanthanum boride. When the content of the lanthanum boride is 6wt%, the hardness reaches its supreme value of 31.83Gpa，its hardness is improved nearly 20.52% compared to monolithic boron carbide. The content of the lanthanum boride does not affect greatly on flexibility strength. However，it gives much effect on fracture toughness. The fracture toughness changes like the form of saw-toothed wave as the content of lanthanum boride increases in the test. When the content of the lanthanum boride is 6wt%, the fracture toughness reaches its supreme value of 5.14MPa.m1/2, which is improved nearly 39.67% compared to monolithic boron carbide materials. The fracture scanning electric microscope analysis of boron carbide-lanthanum boride composite material finds that, with the increasing the content of lanthanum boride, the interior station of monolithic boron carbide is changed. The crystallite arrangement is so compact that pores disappear gradually. The main fracture way of boron carbide-lanthanum boride composite material is intercrystalline rupture, while the transcrystalline rupture is minor, which is in accordance with fracture mechanism of ceramic material. It appears that this change of fracture mode by the addition of lanthanum boride gives rise to the improvement of the fracture toughness.

设定RE35%、Mg6-lO%、Ba4-8%、Si～40%。余量为铁（重量百分数）的稀土钡镁硅铁合金。测得该合金的密度为3.74-4.14g/cme3，其熔化温度范围为1050-1140℃。X射线衍射分析表明其主要物相为FeSi2、Mg2Si、FeSi、RESi2、BaSi2、si及新相Ba5.6Ce2.6si7Mg11。