Effect Of Cold And Heat Treatment On The Structure And Properties Of Zr-based Bulk Amorphous Alloys

Bulk amorphous alloys have great potential application due to their excellent mechanical properties,but the low plasticity far below the glass transition temperature T_g greatly limits the application of amorphous alloys in engineering.Heat treatment is a common method to improve the performance of metal materials.In this paper,(Zr_0.6336Cu_0.1452Ni_0.1012Al_0.12)_97.4Er_2.6 bulk amorphous alloy is selected as the research object.X-ray diffraction?XRD?,differential scanning calorimetry?DSC?,mechanical testing machine,scanning electron microscope?SEM?,electrochemical workstation and other experimental means are used to study the effects of relaxation annealing and cryogenic thermal cycles below T_g on the structure,thermal stability,mechanical properties and corrosion properties of the alloy,and the mechanism of the effects was analyzed.The effects of relaxation annealing and cryogenic thermal cycles on the structure of?Zr0.6336Cu0.1452Ni0.1012Al0.12?97.4Er2.6 bulk amorphous alloy were studied.The experimental results show that the alloy specimens treated by relaxation annealing at T_g or below T_g and by cryogenic thermal cycles are still amorphous.The difference is that the atomic arrangement of the alloy specimens treated by relaxation annealing tend to be ordered while that of the alloy specimens treated by cryogenic thermal cycles tend to be disordered.The effects of relaxation annealing and cryogenic thermal cycles on the thermal stability of?Zr0.6336Cu0.1452Ni0.1012Al0.12?97.4Er2.6 bulk amorphous alloy were studied.The experimental results indicate that the supercooled liquid region?T_x of the as-cast alloy decreases with the increase of annealing temperature and holding time,while?T_x of the as-cast alloy increases with the increase of the number of cryogenic thermal cycles.The results show that the thermal stability of the amorphous alloy will be decreased by relaxation annealing,but the thermal stability of the amorphous alloy will be improved by cryogenic thermal cycles.The effects of relaxation annealing and cryogenic thermal cycles on the mechanical properties of(Zr_0.6336Cu_0.1452Ni_0.1012Al_0.12)_97.4Er_2.6 bulk amorphous alloy were studied.The annealing process below T_g will reduce the free volume of the alloy,reduce the atomic spacing and increase the viscosity,resulting in the decrease in the overall plastic of the alloy at room temperature.It is worth noting that the plastic strain?_p of the alloy after annealing at 500K for 30min is higher than that of as-cast alloy,and the plastic strain?_p is 13.41%for as-cast alloy and 16.44%for as annealed alloy,also,its compressive strength?_bc is 2057.58MPa for as annealed alloy.It is considered that the improvement of the plastic deformation ability of annealed alloy,the homogenization of atomic structure,the precipitation of micro nanocrystals or the components are related to segregation.Moreover,the plastic strain?_p of the alloy specimens in different states can be significantly increased by the cryogenic thermal cycles.For the alloy specimens in different states,when the cryogenic thermal cycles are 90 times,the plastic strain?_p at room temperature reaches 19.08%for the as-cast specimens,and 19.05%for the annealed specimens?500K,30min?.Generally speaking,proper annealing and cryogenic thermal cycles can be used as effective methods to optimize the mechanical properties of the alloys.The effects of relaxation annealing and cryogenic thermal cycles on the corrosion properties of?Zr0.6336Cu0.1452Ni0.1012Al0.12?97.4Er2.6 bulk amorphous alloy were studied by electrochemical workstation.The experimental results show that the self-corrosion potential E_corr of the specimens treated by relaxation annealing and cryogenic thermal cycles is positively shifted,which indicates that the corrosion resistance of the amorphous alloy is enhanced by relaxation annealing and cryogenic thermal cycles.