Study On Friction Stir Welding Of Zr-based Bulk Metallic Glass

How to make larger size bulk metallic glass is concerned in recently years. One method is optimizing alloy component, and the other is welding. Using the superplastic property, we try friction stir welding BMG based on the friction stir welding principle.In this paper, the viscous flow properties of BMG were investigated by means of differential scanning calorimetry, uniaxial GLEEBLE tensile and compressive tests at different temperatures. Below the glass transition temperature, the internal friction of the amorphous alloy is weak and modulus changes gently; in the supercooled liquid state, the alloy changes into viscous flow, during the processing of the transition, internal friction is great, the storage modulus drops sharply, from 50GPa nearly to 0GPa, and the corresponding loss factor rises, at the point of glass transition temperature, the loss modulus reaches the peak;The BMG is hard and has small plastic deformation in the temperature range between room temperature to glass transition temperature; while in the supercooled liquid region, the BMG become softer, show an excellent superplastic deformation ability, the stress is lower and the strain is higher.A non-consumable rotating tool with a truncated cone pin was used in the friction stir processing. Friction stir welding of Zr₅₅Al₁₀Ni₅Cu₃₀ to crystalline aluminum were successful when the tool rotation rate is 1445 rpm, traverse speed of the butt-welding is 14.6 or 22.1 mm/min and the pressure is 20 kN. The larger the diameter of the rotation tool shoulder, the better appearance of the joints.In the weld zone of the joint, the plastic flow pattern is obvious, and the materials here mix well. During the friction stir processing, there is no other crystalline phase and the BMG still is amorphous. Changing the welding pressure, rotating tool and the tool traverse speed can not affect the amorphous structure. The tensile strength of the joints is about 110 MPa, microhardness is HV 90-300, and the mechanical properties are between the BMG and the crystalline aluminum.