| The superior high temperature performance and creep resistance of high Nb-Ti Al alloy make it very promising as aeroengine structural materials.In this paper,a water-cooled copper crucible vacuum induction melting furnace(ISM)was used to prepare Ti-43Al-6Nb-1Mo-1Cr-0.1C(T43-0.1C),Ti-43Al-6Nb-1Mo-1Cr-0.05Y2O3(T43-0.05Y2O3).For two alloys,the as-cast structure,room temperature and high temperature tensile properties,and creep resistance of two high Nb-Ti Al alloys have been studied.XRD,SEM,etc.were used to characterize the microstructure and phase composition of the two alloys,and the tensile properties of the two alloys at room temperature and high temperature(800?,850?)and high temperature(800?,850?)creep properties were tested.Scanning electron microscopy was used to observe the deformation zone structure and fracture morphology of the two alloys,study the fracture mechanism and analyze the strengthening mechanism of C and Y2O3 in the high Nb-Ti Al alloy.The results indicate that the as-cast T43-0.1C alloy and T43-0.05Y2O3 alloy are mainly composed of?(Ti Al)phase,?2(Ti3Al)phase,and?/B2 phase,and the microstructure is mainly?/?2 two-phase distribution Alternate composition,?/B2 phase is distributed at the junction of grain boundaries and the structure segregation is serious,and the distribution is grid-like.The segregation degree of T43-0.1C alloy is less than that of T43-0.05Y2O3 alloy;the content of C in T43-0.1C alloy is relatively low.Carbide phases are observed,and bright white nano Y2O3 particles with needle-like or fishbone shapes are clearly observed in the T43-0.05 Y2O3 alloy structure.The maximum strain of T43-0.1C alloy under room temperature stretching is 0.24%,and the maximum tensile strength is 510MPa.T43-0.05 Y2O3 alloy has a maximum strain of 0.45%and a tensile strength of about 678MPa,all of which are brittle fracture.Under800?tension,the maximum strain of T43-0.1C is 3.90%,the maximum tensile strength is 547.20MPa,the maximum strain of T43-0.05 Y2O3 alloy is 5.95%,and the maximum tensile strength is 650.19MPa.Under 850?tension,the maximum strain of T43-0.1C is4.38%,the maximum tensile strength is 577.78MPa,the maximum strain of T43-0.05Y2O3 alloy is 12.30%,the maximum tensile strength is 620.22MPa,and the two alloys are at fracture occurs in a combination of brittleness and toughness at a high temperature of 800?/850?.The strengthening of the T43-0.1C alloy mainly comes from the solid solution strengthening of C,but 0.1C reduces the room temperature plasticity.The strengthening of the T43-0.05Y2O3 alloy mainly comes from the fine grain strengthening of the Y2O3 particles and the second phase strengthening.The creep performance of T43-0.1C alloy at 800°C is better than that of T43-0.05Y2O3 alloy.The creep stress index of T43-0.1C alloy is 3.23,which is the creep behavior controlled by the dislocation slip mechanism;The creep stress index of T43-0.05Y2O3alloy is 4.38,which is the creep behavior controlled by the dislocation climbing mechanism.The creep performance of T43-0.1C alloy is better than T43-0.05Y2O3 alloy at 850°C.The creep stress index of T43-0.1C alloy is 4.91,which is the creep behavior controlled by the dislocation climbing mechanism;The creep stress index of T43-0.05Y2O3 alloy is 2.69,which is the creep behavior controlled by the dislocation slip mechanism.C plays the role of solid solution strengthening and precipitation strengthening to hinder dislocations,which in turn causes dislocations to accumulate and further hinder the movement of dislocations to improve creep resistance;nano Y2O3particles are strengthened by the second phase,strengthened by fine grains,and refined?2/?.The lamella spacing is strengthened to improve the creep resistance of the alloy.The fracture mechanism of T43-0.1C alloy is the initiation and propagation of cracks at the grain boundary,which eventually causes the separation of the grain boundary.The fracture mechanism of T43-0.05Y2O3 alloy is void nucleation,growth,and interconnection. |
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