Preliminary Study On The Combustion Of Zr-based Amorphous Alloys

Amorphous alloys have many excellent properties due to their long-range disordered and short-range ordered atomic structure.Exploring the new function properties of amorphous alloys is of important scientific significance and application value.In this thesis,the combustion of Zr-based amorphous alloys with different compositional components was experimentally studied by differential scanning calorimetry?DSC?and rapid heating method.In addition,the numerical simulation of the combustion of amorphous alloys was carried out using the fluid dynamics software FLUENT.The experimental results show that the Zr₅₅Cu₃₀Ni₅Al₁₀ amorphous alloy has the ignition point of about 810?885 K under the heating rates higher than2000 K/s,which is much lower than its melting point.However,under the same conditions,the crystallized counterparts will not be ignited.The ignition point of an amorphous alloy is consistent with its crystallization onset temperature T_x at the same heating rate.Moreover,the ignition point has obvious dynamic characteristics and it increases with the increasing of heating rate.The main combustion products of amorphous alloys are identified to be metal oxides and intermetallic compounds.It is indicated that the combustion of an amorphous alloy is a self-propagating chain exothermic reaction that occurs under the activation of the exothermic crystallization enthalpy and the external heat at the heating rate no lower than a certain critical heating rate.The binary Zr₅₀Cu₅₀ amorphous alloy can be ignited at a relatively small heating rate.It has a low ignition point of about 771?801 K in the range of heating rate of 1200?2020 K/s.The other two amorphous alloy Zr₄₈Cu₄₅Al₇ and Zr₅₉Cu₂₀Al₁₀Ni₈Ti₃ exhibit the similar combustion phenomena to the Zr₅₅Cu₃₀Ni₅-Al₁₀ amorphous alloy.It is relatively stable during the combustion process,and a relatively high critical heating rate?>2000 K/s?is required for ignition.The ignition point of Zr₄₈Cu₄₅Al₇ is about 776?842 K,while the ignition point of Zr₅₉Cu₂₀Al₁₀Ni₈Ti₃ is about 812?885 K.The results on the combustion of amorphous alloys formed by adding different elements indicate that the higher the thermal stability,the higher the ignition points and the higher the critical heating rates required for ignition.The numerical simulation is employed to investigate the combustion of amorphous alloys.The simulation results are consistent with the experimental ones,and the temperature distribution of the amorphous alloys during combustion is clearly understood.The simulation results show that an amorphous alloy begins to consume a lot of oxygen during the initial combustion stage.The higher the temperature during combustion of the amorphous alloy,the more oxygen is consumed;at the same time,the larger the temperature increase,the greater the increase in oxygen consumption fraction.