Investigation On Microstructure And Mechanical Property Of Aluminum Matrix Composite Formed By Laser Addictive Manufacturing Technology

Laser forming technology,also known as 3D printing technology,is a new rapid manufacturing technology.It is a hot research topic in many fields,such as aviation,aerospace and mechanical manufacturing.There are two methods in laser forming technology.One is laser metal direct forming;another one is selective laser melting.At present,there are few studies on laser direct forming of aluminum alloys,while the preparation of aluminum alloy by selective laser melting process is mainly focused on the study of optimizing process.Up to now,the micro structure evolution of the sample has been not further studied yet.Based on this,this paper carried out two different kinds of laser forming technology of Aluminum Alloy and aluminum matrix composites.Defect,microstructure difference and forming disciplinarian of two different laser forming aluminum alloys were studied,the influence of reinforcing particles on the micro structure of aluminum matrix composites was also investigated.This work provides theoretical basis for laser forming technology for aluminum alloy and aluminum matrix composites and accumulates some experimental data,which has fundamental and applicable significant.In this paper,aluminum alloy samples have been prepared by direct forming of laser metal,and the influence of different process parameters and material compatibility on the defects was studied.The results shows that when P=900 w,v=200 mm/min,spheroidization is the lightest.When the metal powder and the substrate are same material,the nodulizing reduces.The sample with the lowest defect rate was obtained when P=370 w and v=1300 mm/s.The microstructure and evolution of aluminum alloy and aluminum matrix composites prepared by two different laser forming techniques are analyzed.There are?-Al and Al-Si eutectic in the aluminum alloy sample prepared by laser melting direction forming,and the eutectic Si is coarsened with the decrease of the scanning speed.When aluminum alloy is prepared by selective laser melting,the matrix Al is grown in the form of cellular,and the eutectic Si is distributed at the grain boundary.Compared with the laser metal direct forming,the selective laser melting has faster cooling rate,so the distribution of Si elements in the cellular is uniform.In aluminum matrix composites prepared by selective laser melting,morphology and composition could not been changed by adding reinforced phase particles.The particles will lead to significant grain refinement,increased stress and weaken texture intensity.The mechanical properties of aluminum alloy and aluminum matrix composites fabricated by selective laser melting were studied.The results show that elongation is related to the defect rate in aluminum alloy.The weak texture don't obviously effect on mechanical properties.In this work,the tensile strength of the obtained samples reached about 360 MPa,and the maximum elongation was 8%.With the increase of TiB2 particle content in aluminum matrix composites,the tensile strength increased from 384 MPa to 400 MPa,but its elongation decreased from 7.8%to 4.9%.The bonding force between reinforcement and substrate was 106MPa obtained by calculation,and the combination way should be mechanical combination.