| Magnesium Lithium alloy is the lightest metal structure material. In this thesis, Mg- 8 Li- 3 Zn- x Y(x = 0, 0.5, 1.0, 1.5) alloys are prepared by method of e xtrusion, while the microstructure and mechanical properties of alloy influenced by co ntent of Y are studied. The friction and wear properties of the Mg- 8 Li- Zn- x Y(x =0,0.5,1.0,1.5)alloys are tested, the friction and wear mechanism of the alloys influenced by Y content, load and speed are discussed. Main conclusions are as follows:①In the Mg- Zn- Y ternary alloy phase diagram, W- phase(Mg3Zn3Y2, cubic structure), I- phase(Mg3Zn6Y, icosahedron quasi crystal structure), and Z- phase(Mg12Zn Y, long-range order structure) exist in alloy, respectively. In the extruded alloy, the distribution of the fine mesh W- phase can improve its mechanical properties; and W- phase diffuse in the grain boundary by pinning dislocation and grain boundary during the deformation process, then improve the strength of the al oy.②Friction coefficient decreases with the increase of load, increases with the increase of friction velocity; Erosion rate decreases with the increase of load, decreases with the increase of sliding velocity. In the case of rare earth content is increasing, the friction coefficient of alloy is reduced, wear resistance increase; with the same content of rare earth Y, rotational speed, when load increases, the wear loss increases.③Mg- 8 Li- 3 Zn- x Y(x =0,0.5%,1.0%,1.5%) alloy with the increase of sliding velocity, friction coefficients is reduced, but with the same sliding speeds, alloy with Y = 1.5 has minimum friction coefficient of the alloy. In terms of friction and wear, with the increase of sliding velocity, the wear quantity increase. General theory is that the friction speed has nothing to do with the coefficient of friction, but under certain conditions and environment, friction, velocity affects the stress of two friction surface, which affect the friction coefficient and wear loss.④ With the increase of load, alloy experienced grinding particle attrition, oxidative wear and spalling wear and adhesive wear process es. Through the analysis of the friction surface and wear debris, with the increase of rare earth element Y, alloy’s grain refined, grain boundary increases, and at the grain boundary strengthening dispersoid had pinning effect which improves the surface hardness of the alloy. And with the rare earth add ing, oxygen and sulfur in the air can be combined, which thus reduce the degree of loose materials. Y can also be combined with other impurities, so as to purify the effect of grain boundary, and then improve the hardness and strength. |
