Effect of Si Element on Microstructure and Mechanical Properties of Ti6246 Alloy
In order to improve the mechanical properties of the Ti6246 alloy used in aero-engine blade integrated disk,the influence of Si element on the mechanical properties and silicides precipitation of Ti6246 alloy was studied by SEM and TEM.The composition,structure,and precipitation mechanism of silicides were analyzed by JMatpro software.The results show that the residual creep at 455℃decreases noticeably as the content of Si element increases from 0%to 0.1%(mass fraction,the same below)in Ti6246 alloy.When the content of Si element is 0.2%,there are silicides precipitated in Ti6246 alloy,the plasticity fluctuated at room temperature and the residual creep is little changed compared with the 0.1%alloy.When the content of Si element is 3.0%,the tensile strength of Ti6246 alloy is high,but its plasticity is poor.The residual creep is slightly increases which compared with the alloy containing less than 0.2%Si element,the coarse(Ti,Zr)6Si3(S2 type)silicide appears in the structure.The silicides are precipitated from the liquid phase during the solidification process,rather than from the αp phase and β phase in the Ti6246 alloy containing 3.0%Si element.TEM analysis indicates an incoherent orientation relation between silicides and matrix:(2201)S2～(1011)α;(1120)S2∥(1456)α.The greater bonding between Zr and Si atoms promote the precipitation of silicides.Due to the large amount of(Ti,Zr)6Si3 silicide precipitated in the liquid phase,the Zr element in the solid phase matrix is seriously deficient,so no secondary silicides precipitated in the subsequent aging process.The coarse S2 type silicide has no obvious strengthening effect on grain boundary and α/β phase boundary.Therefore,the creep property of the Ti6246 alloy containing 3.0%Si element is not improved.
high temperature titanium alloystructural analysisTi6246 alloysilicidemechanical properties
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