| Bulk metallic glass has excellent properties such as high strength,high elasticity,wear resistance and corrosion resistance,widely used in microelectronics,sporting goods,medical equipment,and national defense.The limitation of glass forming ability resulted that the size of bulk metallic glass is mostly on the order of millimeters.Super-plasticity in the super-cooled liquid region is used to achieve the upgrade of amorphous size quickly and effectively.By studying the flow under the compression of bulk metallic glass,which is of great significance for research,service and performance optimization of amorphous new materials.In this paper,the effects of temperature and strain rate on the viscous flow behavior of ZT1 alloy in the super-cooled liquid region were studied;The optimum conditions for thermoplastic bonding of ZT1 alloy were studied;The X-ray diffract meter was used to characterize structural change of amorphous state of ZT1 alloy before and after high temperature deformation;Thermal stability of ZT1 alloy was analyzed by DSC;Thermoplastic deformation and thermoplastic bonding of ZT1 alloy were carried out by gleeble 3500 thermal simulation test machine;compression at room temperature was evaluated by AG-1 500 KN universal testing machine;The morphology and composition of bonding interface was analyzed by scanning electron microscope.The following conclusions was drawn:(1)Temperature of non-uniform deformation transformed to uniform deformation and non-Newtonian flow transformed to Newtonian flow increase with increasing strain rate.Temperature of non-uniform deformation transformed to uniform deformation at strain rate 3×10-4 s-1 is between 345? and 360?,and temperature of non-Newtonian flow transformed to Newtonian flow is near Tg;Temperature of non-Newtonian flow transformed to Newtonian flow at strain rate 1×10-3 s-1 is near 390?;Temperature of non-uniform deformation transformed to uniform deformation at strain rate 3×10-3 s-1 is between 380? and 390?,and temperature of non-Newtonian flow transformed to Newtonian flow is near 405?;Temperature of non-Newtonian flow transformed to Newtonian flow is near Tg;Temperature of Non-uniform deformation transformed to uniform deformation at strain rate 1×10-2 s-1 is between 390? and 405?,and temperature of non-Newtonian flow transformed to Newtonian flow is near 415?;Temperature of non-Newtonian flow transformed to Newtonian flow at strain rate 3×10-2 s-1 is near 420?.(2)Strain rate of non-uniform deformation transformed to uniform deformation and strain rate of non-Newtonian flow transformed to Newtonian flow increase with increasing temperature.Strain rate of non-uniform deformation transformed to uniform deformation at 380? is between 3× 10-3 s-1 and 1×10-3 s-1,and strain rate of non-Newtonian flow transformed to Newtonian flow at 380? is near 3×10-4 s1;Strain rate of non-uniform deformation transformed to uniform deformation at 390? is between 1×10-2 s-1 and 3×10-3 s-1,and strain rate of non-Newtonian flow transformed to Newtonian flow at 390? is near 1 ×10-3 s-1;Strain rate of non-Newtonian flow transformed to Newtonian flow at 405? is near 3×10-3 s-1;The strain rate of non-Newtonian flow transformed to Newtonian flow at 419? is near 3×10-3 s-1;The strain rate of non-Newtonian flow transformed to Newtonian flow at 420? is near 1 × 10-2 s-1.(3)There is a specific strain rate at each temperature,below which viscosity hardly changes with the strain rate.The viscosity shows a weak strain rate dependence,indicating that the ZT1 alloy at low strain rate is characterized by Newtonian flow.In the high strain rate range,viscosity is no longer a constant independent of the strain rate.Viscosity has a strong dependence on strain rate.That is viscosity decreases linearly with the increase of strain rate,indicating that the ZT1 alloy at high strain rate is characterized by non-Newtonian flow.(4)By studying the viscous flow behavior of the super-cooled liquid region of ZT1 alloy,the conditions corresponding to the optimal Newtonian flow behavior are T=405?,?=1×10-3 s-1;T=415?,?=3×10-3 s-1;T=420?,?=1×10-2 s-1,and thermoplastic bonding was carried out under the three conditions.By comparing the healing degree of the ZT1 alloy bonding interface,it is found that the best bonding condition is T=405?,?-11×10-3 s-1,and the longest completely healing area is about 820 nm;Followed by T=420?,?=1×10-2 s-1,and the longest completely healing area is about 400 nm;Completely healing area wasn't be found in T=415?,?=3×10-3 s-1.(5)By comparing compression properties after binding,after deformation and at room temperature,it was found that the strength of ZT1 alloy subjected to high temperature deformation did not change significantly,but the plasticity was significantly reduced.Observing the fracture of the sample after the connection,it was found that T=405?,?=1×10-3 s-1 had the best bonding quality,that is,the fracture from the amorphous matrix. |
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