Study On Crystallization Mechanism And Forming Processes Of Amorphous Alloy Prepared By Selective Laser Melting

On Comparison with the crystalline material,bulk metallic glasses?BMGs?generally exhibit high compressive strength,good corrosion resistance,wear resistance and large elasticity.This makes the BMGs present a wide application in industry.To date,most of the BMGs are usually prepared by copper mold casting technology.However,the dimension of as-cast bulk metallic glasses is limited by the critical cooling rate using this method,which restricts the widespread application of the BMGs.The application of Selective Laser Melting?SLM?technology to prepare bulk amorphous alloy can tackle the problem of central cooling rate,and provide an opportunity to accomplish the preparation of bulk amorphous alloy without dimensional limitation.This will devise a new method to promote the application and development of bulk amorphous alloy in industry field.The influence of powders on formed parts during SLM process will restrict the increase of the cooling rate of the molten pool,and thereby cause the crystallization of amorphous alloy.In this paper,SLM of ribbon metal rather than SLM of powder metal is proposed for preparation of amorphous alloy.Ti₄₇Cu₃₈Zr_7.5Fe_2.5Sn₂Si₁Ag₂?Ti47?amorphous ribbons and Fe₇₈Si₉B₁₃ amorphous ribbons are studied as the research objects to investigated the forming mechanism and crystallization of amorphous alloy in SLM process.Amorphous alloy via laser remelting is the basis of amorphous preparation with alloy by Selective Laser Melting technique.In this study,laser remelting was conducted on crystalline Ti47 alloy matrix using a fiber laser with a power capacity of 500 W.The effects of different parameters on the morphology of the molten pool and the crystallization behavior of the molten pool during laser remelting were studied.The results show that the amorphous microstructure of the alloy can be obtained in the molten pool of the laser remelted single track,and the morphology of the molten pool is gradually transformed from the coronal shape to the funnel shape with the decrease of the scanning speed.In the overlap remelting process,when the scanning width is large,the crystallization zone is formed in the remelting zone.The scanning width is relatively small,and the remelting zone in heat affected zone is basically amorphous.This is due to the significant effect of heat accumulation in the small scanning length,and the width of the pool and the width of the scanning are close.In the process of surface scanning,keyhole effect is more prominent due to thermal accumulation,and the penetration depth of molten pool increases significantly,also a small amount of pores present at the bottom of the molten pool.The forming process of laser remelted amorphous ribbons was studied to study the effect of different processes on the formation of laser remelted amorphous ribbons.When laser remelted Ti47 amorphous ribbons,it can be effectively deposited after remelting,and the crystallization in the deposit is less.When laser remelted Fe₇₈Si₉B₁₃?Fe?amorphous ribbons,the amount of deposition is related to the way of fixing the ribbons.When the Fe base amorphous ribbons fixed by laser remelting aluminum foil,there is a large gap between the thin strip and the substrate,and the deposition amount of the substrate surface is very little after remelting.When the laser remelting resistance welding fixed Fe base amorphous ribbons,the gap between the thin strip and the substrate is smaller.The substrate surface has a larger deposition amount after remelting,and the crystallization in the deposition layer is stricter.