黑料网

One of the most vital heated parts of an aeroengine is the turbine disc. The requirements for bearing temperature capability and mechanical qualities of the materials used in turbine discs are becoming more and more stringent as aeroengine thrust weight ratios improve. The powder superalloy turbine disc has exceptional mechanical qualities and hot working properties when compared to traditional cast and wrought superalloys because powder superalloys stand out for their homogenous microstructure, fine grains, and lack of macro segregation. Superalloy made by powdered metalworking is now the material of choice for creating the turbine disc of an aeroengine with a high thrust to weight ratio [1-7]. Due to the usage of crucible materials, which are primarily made of -Al2O3, non-metallic inclusions will be introduced during the manufacturing of powder superalloy. The presence of inclusions obliterates the matrix's continuity and negatively affects the low cycle fatigue performance considerably reducing the material's safety and dependability. Therefore, it is necessary to refrain from including the inclusions. Despite the fact that numerous steps have been taken to control inclusions, they cannot currently be totally prevented. The type, morphology, orientation, size, and location of non-metallic inclusions have a significant impact on the alloy's fatigue life, according to a wide number of results. It is necessary to determine the considered. The evolution law of inclusions in the disc preparation process should also be grasped in order to optimise disc preparation and prevent the inheritance of inclusions into the disc. Therefore, a thorough and organised study of the genetic traits of the inclusions in the disc preparation process is required.

Subjective Heading

Al2O3 inclusions in FGH96 alloy expanded in the direction opposite the stress and grew larger along the one-dimensional direction during HIF, according to Zhou Guo discovered that the inclusions in the FGH95 alloy would not deform following direct hot isostatic pressing, but did so following forging when they were lengthened horizontally perpendicular to the forging direction and could be entirely broken by extrusion and forging. According to Zhang during the HEX process along the extrusion direction, Al₂O₃ non-metallic inclusions stretched into a discontinuous linear shape. Large hot extrusion deformation was able to successfully break the non-metallic inclusions and raise the purity level of FGH9₆ disc. Wang confirmed that the inclusions could be broken during the extrusion process. FGH9₆ metal. Extrusion and forging procedures were found to be able to reduce the size of inclusions when computed tomography was utilised to evaluate the three-dimensional shape of inclusions under various process conditions. After deformation during HEX, Kantzos discovered that the inclusions were efficiently broken and extended along the extrusion direction in a linear distribution. The inclusions were dragged in a onedimensional direction for a longer period of time as the deformation increased. Bonacuse used a metallographic technique to observe the inclusions' three-dimensional dimension and discovered that their orientation matched the direction of excessive strain [8-12]. According to the NASA report the inclusion's three-dimensional size and morphology were determined by compiling the data collected by the metallographic approach. This technique was used by kantzos to quantify the inclusion's three-dimensional size during forging deformation. The three-dimensional size seen by the metallographic approach is still unknown, though, because the seen surface is not always the greatest portion of the inclusion. Future research on PM superalloys will concentrate on accurately defining the 3D morphology of inclusions and establishing the quantitative relationship between thermal process parameters and the change in inclusion size. Although many experimental researches on the deformation behavior of nonmetallic inclusions in HIP, HIP + HIF and HIP + HEX have carried out, there is still a lack of research on the quantitative relationship of the size change of the inclusions during deformation process, and the accurate characterization of three-dimensional morphology.

Discussion

By using a nano indentation test, the micro mechanical characteristics of Al₂O₃ inclusions and the alloy matrix were identified. According to the findings, the elastic modulus and nanohardness of Al₂O₃ inclusions were 38.9 GPa and 324 GPa, respectively, while these values for the alloy matrix were 15.6 GPa and 206 GPa. Al₂O₃ inclusions had substantially better hardness and strength than the alloy matrix, and they had comparatively low plasticity [13-15]. The inclusions ruptured when the alloy distorted as a result of a strong external force.

shows SEM pictures of inclusions in several extruded billet sections in a direction parallel to the extrusion. Al₂O₃ inclusions were shattered during hot extrusion, and they lengthened parallel to the direction of extrusionthe flow of the matrix alloy to some extent disseminated the inclusion particles. As shown in when the inclusion size was 30 m, the diameters of the inclusions in the core, 0.5R, and rim of the billets were 48 m, 50 m, and 68 m, respectively According to the size of inclusions in the core, 0.5R, and rim of the billets along the deformation direction were, respectively, 165 m, 181 m, and 187 m when the inclusion size was 60 m.The size of the crushed inclusion particles along the extrusion direction increases with the original size of the inclusion. From the core to the rim, inclusion sizes slightly grew.

Due to the shear effect of friction at the extrusion die and the press force on the billets, the alloy in the centre of the billets flowed first during the hot extrusion process, and the flow velocity vx was the quickest. According to equation .When the alloy's flow velocity vx steadily dropped from the core to the rim, the inclusions were subjected to the shear stress x brought on by the disparity in flow velocity along the alloy's flow direction, and they grew longer. x is the strain of the alloy in the x direction, x is the shear stress of the alloy in the x direction, and x is the fluid viscosity.

Conclusion

Similar to hot extrusion, during isothermal compression, the Al₂O₃ inclusions with diameters of 30 m and 60 m gradually tilt and distort with alloy flowing because of the variation in flow velocity in different portions of the alloy. It was discovered that the tilt angle of inclusions in the HEX state is 0°, the tilt angle when the deformation is 20% is around 15°, the tilt angle when the deformation is 50% is about 45°, and the tilt angle when the deformation is 75% is about 90°. Inference: The inclusions were more extended in the X and Y planes when the deformation was above 75%. Observing the projection area of inclusions in the X and from the isothermal compression direction

Acknowledgement

I would like to thank my Professor for his support and encouragement.

Conflict of Interest

The authors declare that there are no conflicts of interest.

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