Study On The SiC_p Reinforced Al-Mg Alloys And Filler Wire Contain SiC_p

Aluminum alloy,a kind of important structure of lightweight materials,is widely used in automobile industry,marine,rail transportation and aerospace industries.The traditional aluminum alloy with low strength,stiffness,higher thermal expansion coefficient,and hot cracking during welding can't meet the needs of the development of modern industry,which limits the widely application of aluminum alloy as structures materials.In recent years,many studies have shown that mechanical property and weldability of aluminum alloy could be improved by adding ceramic particle.In this article,the SiC_p/Al-Mg and SiC_p/Al-Mg-Sc-Zr composites with submicron-SiC particles were prepared by semisolid stirring assisted ultrasonic processing.Optical microscope?OM?,scanning electron microscope?SEM?,tensile test,Vikers hardness test and etc.were employed to research the microstructures and property of the alloy and composites.The composite tungsten insert gas?TIG?welding filler was fabricated by rolling process.Aluminum alloy?2024-T4?was TIG welded using those filler wire.Effects of the SiC particles additions in filler wires on the microstructures and properties of TIG welds of 2024-T4 were investigated.Some important conclusions wre obtained as follow.?1?For SiC_p/Al-5Mg composites,the grains were refined and most of SiC particles distributed along the grain boundaries.The ultimate tensile strength,yield strength and elongation of the SiC_p/Al-5Mg composites were simultaneously improved due to the grain refinment,which could be attributed to the heterogeneous nucleation and the inhibited growth of grains caused by submicron SiC particles.?2?Interphase precipitation was suppressed because of the existence of SiC particles in the grain boundary.As a result,the corrosion resistance of SiC_p/Al-5Mg composites was improved.The composite has a poor bead geometry due to SiC particles,but the crack and porosity are limited.The fusion zone of the composite becomes fine grain,due to nucleation catalysis by SiC particles.These results indicated that SiC_p/Al-5Mg composite had good weldability and corrosion resistance.?3?Rolling process can significantly refine grains and modify distribution of the reinforcements.After welding,a fully equiaxed grain structure were formed across the entire welds with additions of SiC particles in filler wires and the amount of eutectic phase along grain boundaries reduced.The ultimate tensile strength and elongation of weld metals were increased greatly.?4?A lot of granular eutectic Al₃?Sc,Zr?distributed in the grain boundary of Al-5Mg-0.35Sc-0.1Zr alloy.The introduction of SiC particles could refine the grain and avoid the appearance of eutectic Al₃?Sc,Zr?.In fusion zone of TIG welding,the second phase were short rod-shaped or granular,but the SiC_p/Al-5Mg-0.35Sc-0.1Zr filler could result in more refined grain and better mechanical properties.