In-Situ Study On Mechanical Properties And Corrosion Failure Behavior Of Super-Light Magnesium Lithium Alloy

Known as super-light alloy,Magnesium lithium(Mg-Li)alloys are the lightest metal structural material up to now.Magnesium lithium alloy not only possess virtues such as low density,high specific stiffness,high specific strength,high specific modulus,cold forming ability,but also have virtues of good electrical conductivity,thermal conductivity,shock absorption and electromagnetic shielding properties.Mg-Li alloys have excellent application prospects in the fields of telecommunications electronics industry,military and aerospace,automotive,medical equipment.However,the disadvantages of magnesium-lithium alloys,such as low strength,poor corrosion resistance and poor thermal stability have limited their wider application.Therefore,it is necessary to design alloys with comprehensive mechanical properties to meet the requirements of practical application of Mg-Li alloys.In real production,whether plastic processing of metal materials or metal materials for intensive processing to obtain better mechanical properties,we need to understand the metal plastic deformation mechanism.In-situ experiments can combine the loading effect with the microscopic testing of the surface structure of the material,so we can observe the evolution of deformation and damage on the surface of alloy samples during loading process.We can investigate the dynamic evolution of microscopic deformation mechanism of the dual-phase magnesium-lithium(Mg-Li)alloy under static load and alternating load by optical microscope(OM).In the mean time,we can study the plastic deformation and failure of the micro-master mechanism deeply to provide theoretical guidance for the design and development of high-performance magnesium lithium alloy.The results show that under static and alternating loads,the deformation mechanism of the dual-phase Mg-8Li alloy is dominated by dislocation slip.Under alternating load,the alloy will also produce twins and cross-slip deformation to coordinate deformation.The as-cast Mg-8Li alloy is ?+? phase structure.The failure mode of the alloy during the stretching process is mainly grain boundary cracking.In-situ tensile tests show that the plastic instability of as-cast Mg-8Li alloy at low strain rate is related to the density of dislocation slip.Quasicrystal can inhibit the generation of dislocation of alloy,improve the mechanical properties of as-cast Mg-8Li alloy,affect the plastic deformation and failure behavior of alloy.Under static loading,the a phase of the quasicrystalline as-cast Mg-8Li-10Zn-Y alloy generate grain boundary sliding.The second-phase and the I-phase will crack.Fatigue cracks in the as-cast Mg-8Li-10Zn-Y alloy can initiate at the alloy surface and casting defects,and fatigue failure occurs in the quasi-crystalline phase.In order to study the effect of quasicrystal on the corrosion resistance of the alloy,we study the two alloys about the immersion test,electrochemical experiment and alloy immersion corrosion in NaCl solution.The results show that quasicrystal will reduce the corrosion resistance of the dual-phase Mg-8Li alloy.