Microstructure Control And Properties Of Bulk CuZr-based Amorphous Composites

CuZr-based amorphous composite materials have received extensive attention at home and abroad due to their excellent properties,and their excellent room-temperature shaping and mechanical properties are closely related to their endogenous crystal phase B2-CuZr,the studies find that the mechanical properties of the CuZr-based amorphous composites material mainly depend on the amount of endogenous B2-CuZr precipitation(volume fraction)and its uniformity,improving the uniformity of B2-CuZr distribution in large-scale sections have become the key to further improve the mechanical properties of amorphous composites.For this reason,Cu-Zr-Al based amorphous alloys are selected in this paper.By studying the effects of solidification cooling rate,the amount of heterogeneous nucleus element Ta,and the remelting constant temperature treatment process on the uniformity of B2-CuZr distribution in the sample cross section,which provides experimental basis for the preparation of B2-CuZr/CuZr-based amorphous composites with large scale,uniform distribution of B2-CuZr cross-section and high mechanical properties.Firstly,in this paper,samples of(Cu0.47Zr0.47Al0.06)99.1Ta0.9 alloy rods with different diameters d=2mm,3mm,3.4mm,4mm have made by suction casting.The influence of equal amount of heterogeneous nucleus element Ta on uniform B2-CuZr under different cooling rates are studied,the results show:a single B2-CuZr phase is precipitated in different sizes of amorphous composite samples prepared by vacuumsuction casting.There is a d=3.193×1011·/T-3.6621 relationship between the average diameter of the precipitated B2-CuZr particles in the melt and the solidification cooling rate;The mechanism of the B2-CuZr phase in the cross section of the Ta uniform amorphous composite is that the coherent element Ta provides uniformly distributed heterogeneous nucleus particles,promotes the nucleation of B2-CuZr and makes it uniformly distributed.However the effect of equal Ta uniform B2-CuZr phase is strongly restricted by the solidification cooling rate,Only under the solidification cooling rate that matches the amount of Ta,the effect of Ta to promote B2-CuZr nucleation and the uniform cross-section B2-CuZr distribution can be reflected;The solidification cooling rate matches with 0.9at.%Ta is the solidification cooling rate corresponding to the diameter d=3.4mm sample,and its theoretical calculation is about 520K·S-1.Secondly,by preparing ?4 mm(Cu0.47Zr0.47Al0.06)100-xTax(x=0,0.25,0.5,0.75,0.9,1)alloy samples,The influence of Ta on the structure and performance of large-scale samples have studied.The results:with the increase of the amount of Ta,the precipitation amount of B2-CuZr phase in the cross section of the alloy sample increases,The distribution uniformity of B2-CuZr phase in the cross section decreases,At the solidification and cooling rate corresponding to the(p=4 mm alloy sample,the theoretically calculated value of 293K·S-1,the matching Ta addition that makes the B2-CuZr phase section more uniformly distributed is 0.25at.%.The mechanical properties and corrosion resistance of the amorphous composite samples depend on the precipitation amount(volume fraction)of B2-CuZr and the uniformity of its cross-sectional distribution,The best Ta addition for better mechanical properties is 0.5at.%,and the plastic strain and fracture strength of the samples are 1.06%and 1869Mpa,a suitable amount of Ta improves the uniform distribution of the B2-CuZr phase in the amorphous composite material,and also decreases the corrosion resistance of the amorphous composite material.On this basis,(Cu0.47Zr0.47Al0.06)99.5Ta0.5 amorphous alloy is selected,and the remelting and isothermal treatment process is carried out to study the microstructure of the amorphous composite material.the results show:near liquidus isothermal treatment and rapid quenching process can make the B2-CuZr cross section uniformly distributed.However,the remelting constant temperature treatment and water quenching process fail to obtain a single strengthening phase B2-CuZr on the amorphous matrix due to the slow cooling rate of the water quenched sample.For this reason,this paper proposes process improvement measures such as shortening the air-cooling time of the quick-quenching sample,quickly bringing the packaged sample directly into contact with the quick-quenching medium,using a high-cooling rapid-quenching medium,and appropriately increasing the constant temperature processing temperature.