Glass Forming Ability And Thermal Stability Of Al-based Amorphous Alloy

Al-based amorphous alloys A1-RE-TM(RE represent rare metal,TM represent transition metal) produced by rapid solidification exhibit properties with high intensity, good toughness and low density and have generated considerable research and usages in recent years.Al-based amorphous alloys appear that a multicomponent combination of constituents with large atomic size differences(i.e>12%) and a negative heat of mixing are key factors favoring galss formation. With the three component design rules of Inoue, two Al-based alloys of Al₈₀Ni_15-xY₂Zr₃Cu_x (x=0,1,3,5,6,7,9) and Al₈₀Ni₁₀Y_5-xZr_xCu₅(x=0,l,2, 3,4) were designed, the ribbons(breadth is 3mm, thickness is 50 65um) of which were produced by rapid solidification had been investigated by XRD, DSC, DTA and SEM methods.The glass forming ability and thermal stability of the alloys were investigated, the effect of Cu and Zr on the glass forming ability and thermal stability of the alloys were investigated, the mechanisms of the glass formation were discussed and the vitrification of the alloys were also been done.The results indicated that all of the alloys that had been investigated have certain glass forming ability and thermal stability: To Al8oNi_15-xY2Zr₃Cu_x(x=0,l,3,5,6,7,9), proper Cu addition increased the glass forming ability of the alloy, which deceased when the Cu addition is too low or high. With the increase of the Cu content (x varies from 0 to 9)., the thermal stability of the alloy were decreased. The GFA and thermal stability of the alloy systems are not change in the same way, and they depend on different mechanisms;To Al₈₀Ni₁₀Y_5-xZr_xCu₅ (x=0,l,2,3,4), the glass forming ability of the alloy were increased with proper Zr addition. With the increase of the Zr content, the thermal stability of the alloys were increased (x varies from 0 to 2), which decreased a little then (x varies from 2 to 3 ).The increase of the thermal stability of the alloy systems with Zr addition are due to the higher melt temperature of Zr(1852°C) than Y(1522°C) and the decrease of them are due to the separate out of the a -Al at lower temperature or the formation of phases instability.The results of the verification to the Al₈₀Ni₁₀Y₂Zr₃Cu₅ amorphous alloy indicated that the separate out of the phases are different with different verification phases, the crystallization can be divided into three phases , which corresponding with the separated out of a-Al; a-Al+Al₃Ni; a-Al+Al₃Ni+Ni+3Y+Al3Zr₂ in turn.