Study On Alloying And Solid-state Composite Processing Of Mg-Li Alloys

Magnesium-lithium alloys are the lightest structural material among the alloys.It possesses low density, high specific strength and specific rigidity, good damping capacity and high energetic particle penetration resistance, as well as recycling property. Based on these advantages of Mg-Li alloys, they have good prospect of applications in the fields of aerospace, electronic industry, military, et al.The strength and the corrosion resistance of the ternary alloys were studied by alloying the Mg-Li alloy with various componential Al or Zn, respectively. In this thesis, in order to refine the grains, Ce and Y were added in the alloys, and the strength and elongation of alloys were improved.Then, in order to increase the strength of Mg-Li alloys,the Mg-Li matrix composites reinforced with B4C particles were studied with hot-extrusion solid-state composites processing.Alloys were prepared by induction melting method under an argon atmosphere.Microstructures were measured with optical microscope and scanning electron microscope.Phase analysis was done with X-ray diffraction. The mechanical properties of these alloys were measured with a tensile tester (2 mm/min of the tensile speed).The results show that:1.While the amount of Al and Zn are 1%,the as-rolled Mg-8Li-lAl alloy with a thickness of 0.16 mm has the highest tensile strength (313.9 MPa),the as-extruded Mg-8Li-1Zn alloy with a thickness of 3 mm has the maximum elongation (44.0%),The as-rolled Mg-8Li-lAl-1Zn alloy with a thickness of 0.18 mm has both high tensile strength and high elongation (233.4MPa and 9.2%, respectively).2.AlCe phase dispersively distributes in the matrix with the addition of Ce. The grains of the alloys are refined, and the mechanical properties of the alloys are improved.The amount of AlCe phase increases with the Ce content, and the grains are refined obviously.Mg-8Li-1Al-0.6Ce alloy possesses the highest strength and the maximum elongation. The excess AlCe phases are produced, and they segregate at grain boundary.Therefore, the matrix is dissevered, and the strength of alloys decreases.3.The working hardening and dislocation tangle are the main factors which cause that the strength of the alloy is increased and the elongation of the alloy is reduced, after Mg-8Li-1Al-0.6Ce was rolled. The recrystallization is primary factor which causes that the strength and the plasticity of alloy are increased, after the alloy is annealed.4.B4Cp/Mg-8Li-1Zn, B4C/Mg-8Li-1Al-0.6Ce and B4Cp/Mg-8Li-lAl-lY composites are prepared with hot-extrusion solid-state composites processing. With the parameters of preforming and the deformation being optimized, the deformation and the migration of a phase are improved, and the amount and the size of gaps is decreased.Therefore, the bonding force of foils is improved, and the oxidation of foils is lowered.The strength of the B4Cp/Mg-8Li-1Zn and B4Cp/Mg-8Li-lAl-lY composites is increased obviously after extrusion (246.1MPa and 257.2MPa, respectively).The results show that the interfacial bonding of the composites is improved.