Research On The Microstructure And Properties Of CoCrFeMnNi High-Entropy Alloy Heterogeneous Laminated Structure

This topic starts from improving the strong-toughness plastic matching relationship of CoCrFeMnNi high-entropy alloy,and explores a new process parameter for preparing heterogeneous laminated structure high-entropy alloy sheet.Magnetic levitation smelting technology is used to obtain a CoCrFeMnNi high-entropy alloy ingot with a uniform structure,and then the ingot is cold-rolled and annealed to recrystallize;a new process is innovatively designed,that is,laminated cold-rolled and annealed plates,through Hot-press welding,coldrolling deformation,combined with the final heat treatment process,successfully prepared a heterogeneous laminated structure CoCrFeMnNi high-entropy alloy sheet.Using optical microscope,electron backscatter diffraction analysis technology,transmission electron microscopy and other characterization methods,the structure of the as-cast,cold-rolled and annealed states,and the interface welding situation of the hot-press welding joints were analyzed.The microhardness tester and the tensile test were used.The testing machine analyzes the mechanical properties and organizational structure of the heterogeneous structural plates,and obtains the following conclusions:(1)The hot pressure welding process of laminated small cylinders is closely related to the holding time and the diameter of the small cylinder.Too short holding time causes temperature gradients in the core and surface of the small cylinder,which will cause cracking and misalignment problems;small cylinder diameter Too small will cause misalignment of the small cylinder during the hot-pressing deformation stage and aggravate edge cracking.When the holding time is extended to 30 min and the diameter is increased to 15 mm,the small cylinder will no longer be misaligned when deformed by hot pressing;(2)After adjusting the heat treatment process,the high entropy alloy with special microstructure was successfully prepared,and the microstructure difference between layers was retained;The existence of interface between layers and the structure of hard phase surrounding soft phase in the layer contribute to the accumulation of geometrically necessary dislocations;(3)One of the novelties of the heterogeneous laminated structure is the structural differences between layers,including grain size,dislocation density,etc.;second,the structure in the layer has a special structure of "hard phase surrounding soft phase",which benefits from the particularity of the preparation process.In addition,the heterogeneous laminated structure contains many interfaces,that is,the interfaces between layers.These particularities all contribute to the generation and storage of geometrically necessary dislocations to coordinate plastic deformation.It is also found in the actual mechanical performance test that its deformation hardening ability has been improved.