Laser 3D Printing Of Zr-based Bulk Metallic Glass

Bulk metallic glasses?BMGs?have attracted great interests due to their remarkable mechanical,physical,and chemical properties.The small dimensions,simple shape,and poor plasticity at room temperature severely limit their scope of industrial application,fabricated by the traditional methods such as copper mould casting method.Laser three-dimensional?3D?printing technology,also known as additive manufacturing technology,provides an opportunity to fabricate BMGs without any dimensional constraint.In present work,an excellent glass-forming composition Zr₅₀Ti₅Cu₂₇Ni₁₀Al₈?Zr50?designed by the method called“proportional mixing of binary eutectics”provides a brilliant material prepared by gas atomization method for laser additive manufacturing to achieve full or near full amorphous alloy.Firstly,the temperature field of laser melting deposited single track on the amorphous alloy substrate with same nominal composition is researched by finite element method?FEM?simulation.The crystallization zone resulting from FEM data processed by Matlab coincides with the result of experiment measured by BSE-SEM.The optimal parameters in the laser 3D printing of Zr50 amorphous alloy process is estimated by our crystallization prediction method on laser 3D printing of BMGs.Combined with FEM,the Kempen crystallization kinetic model is introduced to discuss the crystallization behavior of Zr50 amorphous alloy during laser 3D printing process,getting a calculation result of kinetic equation which is approximate to the experimental results,analyzing the reason of the inevitable crystallization of Zr50 amorphous alloy during laser 3D printing process from the kinetic point of view.Then,multilayer Zr50 amorphous alloy is melting deposited on the 45#steel by laser 3D printing method,studying the effect of parameters on forming and crystallization behavior of Zr50 amorphous alloy.With the invariant scanning speed,the thickness of printing layer has little change,the thickness of crystalline region in heat affect zone increases,and the crystalline ratio increases as well,when the laser power increases.With the invariant laser power,the thickness of printing layer and crystalline region in heat affect zone increases and the defects in the interlamination increases as well.When the laser power is 200 W and the scanning speed is up to 800 mm/min,the crystallization ratio of laser3D printing Zr50 amorphous alloy is the smallest.Finally,the structure of the samples with laser power of 200 W and scanning speed of 800 mm/min is studied.Crystallization phase of amorphous alloy prepared by laser 3D printing shows periodic gradient distribution,and the crystallization phase ratio and size reaches the maximum value at the interface of the melting pool and the heat affected zone,the hardness of the samples reaches the maximum value thereupon.The maximum hardness of each layer decreases with the increasing of the distance from the substrate.