Research On Fiber Laser Welding High Entropy Alloys CoCrCuFeNi Thin Sheet

Compared to conventional alloy,high entropy alloys are considered to have higher hardness,compressive strength,ductility and thermal stability,which can be promisingly applicated in many aspects due to their high temperature resistance,high wear resistance,high corrosion resistance,high radiation resistance and other excellent properties.Laser welding technology is an important method for metal forming,and has been widely used in a variety of materials in the welding process.However,the laser weldability of High entropy alloys has not been investigated systematically and specifically until now.Therefore,it is significant to study the laser weldability for expanding the application field of high entropy alloys.The high entropy alloys Co Cr Cu Fe Ni have been studied in this paper,which is welded by single fiber laser butt welding and laser remelting.The influence of solidification mode,process parameters on the welding seam,and the mechanical properties,wear resistance and corrosion resistance of prepared laser remelting layers have been investigated using the optical microscope,scanning electron microscope,X-ray diffraction analyze,integrated test system of nanomechanics,wear tester and electrochemical test station.The obtained results are shown as follows: the crystal structure of cast high entropy Co Cr Cu Fe Ni alloys is dendrite phase structures,rich-Cu phase distributing in the space outside the dendrite phases.The weld profile of high entropy alloys Co Cr Cu Fe Ni in laser welding exhibited a typical "T" shape,and the crystal structure of welding seam are the mixture of dendrite structures,including that one grows perpendicular to fusion line at the edge of fusion zone and another is equiax dendrite at the center of fusion zone which has an average grain size of 3.3 ?m.After laser welding,the composition of the fusion zone is homogenized,and the segregation of Cu element reduced.As the laser power increases,the penetration depth,bead width,waist width and depth of waist show an increasing trend;as the weld speed increases,the penetration depth,bead width,waist width and depth of waist show a decreasing trend.The laser power plays a more important role in deciding the penetration depth,while the weld speed has a more important impact on the bead width,waist width and depth of waist.The laser power and weld speed have little effect on the hardness of fusion zone,which is harder than parent metal.The average hardness of fusion zone is165.86±8.66 HV,while average hardness of parent metal is 143.83±3.43 HV.The yield strength of laser remelting layers of high entropy Co Cr Cu Fe Ni alloys are higher than that of parent metal,which are 262.83±36.24 MPa and 125.94±23.56 MPa,respectively.Also,the friction coefficient of laser remelting layers is lower that of parent metal,which are 9.02±0.42 mg and 7.73±0.29 mg,respectively.The wear mechanism is dominated by adhesive wear and abrasive wear.The high entropy alloys have the better corrosion resistance in salt solutions,and most easily trends to be corroded in alkali solution,and the fastest speed of corroding in acid solution.The laser remelting layers have the faster corroding speed and the more likely to be corroded that other areas.The corrosion potential of the laser remelting layer is-0.3002 to-0.2439 V,and the corrosion potential of the parent metal is-0.2090 V.The average corrosion current of the laser remelting layer is 1.485×10-6A,and the corrosion current of the parent metal is 2.9145×10-8 A.