Role Of Various Alloying Elements On Microstructure And Properties Of Co-Ti-V Superalloy

The morphologies of?'phase,the lattice misfit between?/?'two-phase,the partitioning behavior of elements,the solvus temperatures of?'phase and high temperature mechanical properties of the Co-Ti-V-based superalloys with varied Hf,Re,Ru,Ta and Ni contents were investigated by SEM,XRD,TEM,DSC and high temperature compression tests.The main conclusions are as follows:The Hf and Re elements within 1%(at)are added to the Co-based superalloy,and the?base phase and??reinforced phase are precipitated in the alloy,and no other impurity phase is precipitated.As the Hf and Re contents increases,the lattice misfit between?/??two-phase decreases.Co,Hf and Re exhibit a tendency to partition into?phase and richened in the?phase.Ti and V exhibit a tendency to partition into??phase and richened in the??phase.Besides,Re has a facilitate effect on the partitioning of Ti and V elements.Compared with the base alloy,the room temperature Vickers hardness of the alloys of the other four components has increased to varying degrees.Among the five alloys,1%Re has the highest room temperature Vickers hardness.With the increase of Hf content,the yield strength and ultimate strength of the alloy show the tendency of decreasing first and then increasing.Yield strength and ultimate strength of 1%Hf alloy were highest among the alloy with varied Hf content.With the increment of Re content,the yield strength and ultimate strength of the alloy show a linear increase.The alloy contains Ru element within 1%(at),the alloy structure is mainly composed of?base phase and??reinforced phase.The alloy contains Ta element within 1%,Co3V phase is also formed in the alloy.With the increment of Ru and Ta contents,the lattice misfit between?/??two-phase increases.Ru and Ta tend to partition into??phase and richened in the??phase.Besides,Ru and Ta play a role in promoting the partitioning of Ti and V elements.The T_solvus-??of 0Ru,0.5%Ru and 1%Ru alloys were obtained about 1103?,1104?and 1101?,respectively.When the Ru content rise from 0 to 0.5%,the Vickers hardness of alloys increases,but when the Ru content increases to 1%,the Vickers hardness of alloys decreases slightly.With the increment of Ta contents,the Vickers hardness of the alloy showed a significant upward trend.Among the five alloys,2%Ta has the highest Vickers hardness of room temperature.With the increment of Ru contents,the yield strength and ultimate strength of the alloy show the tendency of increasing and decreasing.Among alloys with varied Ru content,the yield strength and ultimate strength of the 0.5%Ru alloy are the highest.When the Ta content rises from 0 to 1%,the yield strength and ultimate strength of the alloy increase significantly.After high temperature compression test,??phase of 0.5%Ru alloy and 1%Ta alloy insypheberate less shear,dislocations can not effectively cut the??phase,so that the??phase shape of the crucible is basically kept complete,so it can play a better reinforcement role.The alloy contains Ni element within 10%(at),the alloy structure is mainly composed of?base phase and??reinforced phase.With the increment of Ni contents,the lattice misfit between?/??two-phase increases decreases.Ni tends to partition into??phase and richened in the??phase.The solvus temperatures of??phase were measured to be 1167?,1114?,1108?for the 0Ni,5%Ni and 10%Ni alloys respectively.Compared to the base alloy,the Vickers hardness of room temperature both 5%Ni and10%Ni alloys increased significantly.Among the three alloys,10%Ni has the largest Vickers hardness of room temperature.With the increment of Ni content,the yield strength and ultimate strength of the alloy show the tendency of decreasing first and then increasing.And the yield strength and ultimate strength of10%Ni alloy were highest.After high temperature compression test,both the base alloy and the 10%Ni alloy can be miscut,but the shape of the phase of the??phase is not changed much,so the??phase can play a certain reinforcement effect.