Effect Of Ta Addition And Temperature On The ?? Phase Morphology And Structure In Co-8.8Al-9.8W Alloy

The development of the aerospace industry is closely related to the research status of superalloys.The research and development of superalloys with excellent properties is a prerequisite for manufacturing high-quality aerospace engines.At first,nickel-based superalloys were widely used because of their?/?'two-phase coherent strengthening mechanism.However,due to the limitation of their temperature bearing capacity,the development of nickel-based superalloys reached a bottleneck period.Until 2006,a new?/?'two-phase structure similar to that of nickel-based superalloys was found in the new Co-Al-W cobalt-based superalloys.This is different from the traditional cobalt-based superalloys strengthened by carbide dispersion and solid solution of alloying elements,and the melting point of cobalt is 40°C higher than that of nickel,which is a major turning point for the temperature bearing capacity of superalloys,so it has received close at tention from scholars at home and abroad.By studying the effect of the alloying element Ta on the microstructure of the strengthening phase?'in alloy Co-8.8Al-9.8W,the following research results are obtainedAfter adding alloy Co-8.8Al-9.8W in the different Ta contents,phase compositions are basically the same after 1300?/8h solid solution treatment and900?/50h aging treatment,which all have?-Co solid solution,strengthening phase(Al,W),metastable ordered precipitated phase Co ₃Ta,and carbide Co Cx formed due to the introduction of C element during the smelting process.With the increase of Ta content,the?'phase dissolution temperature of the alloy first decreases and then increases,which also has a greater impact on the solidus temperature of the alloy.The solidus temperature of the 1.5Ta alloy is the lowest,and the 1Ta solidus temperature is the highest;the morphology of the?'phase in the matrix alloy Co-8.8Al-9.8W is cubic.With the increase of Ta content,its cubic morphology does not c hange much,and?'phase precipitates uniformly on the matrix,and its morphology remains highly consistent.The addition of Ta element will affect the crystal orientation of the alloy Co-8.8Al-9.8W.The crystal orientation in the 0Ta alloy and the 0.5Ta alloy is the same,both of which are[011],while the crystal orientation is the same in the 1Ta,1.5Ta,and 2Ta alloys,both of which are[001].The addition of more or less Ta content will inhibit the solid solution and diffusion of Al in the Co matrix.The 1.5Ta in this experiment is more beneficial to the solid solution of Al in the?-Co matrix.The phase composition of Co-8.8Al-9.8W-1.5Ta alloy after solution treatment at different temperatures has?-Co solid solution,strengthening phase?'-Co₃(Al,W),and metastable ordered precipitated phase Co ₃Ta and carbide Co Cx formed due to the introduction of C element during the smelting process.Based on 1300?,if the temperature is too high or too low,the volume fraction of the??phase will be reduced,and the morphology of the??phase will tend to be circular,while the morphology of the?'phase in the 1300?alloy will remain highly cubic.If the temperature is too low,the structure and size of the?'phase in the alloy will be uneven,and if the temperature is too high,the structure and size of the?'phase in the alloy will be extremely uneven.The crystal orientations in the alloys prepared at 1250?,1270?,1300?alloys and solid solution temperatures of 1350?are consistent,and all are[001],which are different from the crystal orientations in 1330?alloys,that is[1 12].Increasing and decreasing the temperature will reduce the solid solution degree of Al in the matrix,and make the entire strengthening phase??-Co₃(Al,W)bias to the existence of Co₃W.