Thermal stabilities of microstructure and mechanical property have been investigated on super- alloy U72OLi, which is of great interest of application for jet engine and land-based turbine disc. The results showed tha...Thermal stabilities of microstructure and mechanical property have been investigated on super- alloy U72OLi, which is of great interest of application for jet engine and land-based turbine disc. The results showed that, the primary and secondary γ’?particles maintain good thermal stability at 650 and 7000C with aging time up to 3000 h, while the tertiary γ’?is apparently dependent on aging temperature and time. The tertiary γ’?particles undergo a procedure of coarsening, dissolution and eventually complete disappearance with the increasing of aging time and temper- ature. They exhibit unusual high sensibility upon aging temperature, which is attributed to the lattice misfit between the γ’?precipitates and the matrix in the alloy. The grain boundary phase M23C6 remains stable without forming of sigma phase even with aging time up to 3000 h at 700℃. Microhardness decreases apparently with increasing aging time and aging temperature. Theoretical analysis based on dislocation mechanism indicates that the change of microhardness should be attributed to the evolution of the tertiary γ’?during aging.展开更多
Constant load creep tests on isothermally forged Udimet 720Li, an advanced superalloy for gas turbine disc application, were run in the stress/temperature field 900-450MPa/650-700 ℃ producing rupture times in the 20-...Constant load creep tests on isothermally forged Udimet 720Li, an advanced superalloy for gas turbine disc application, were run in the stress/temperature field 900-450MPa/650-700 ℃ producing rupture times in the 20-5000h range. The creep curves have shown a predominant accelerating creep stage, that has been described by the following equation: where ε min depends on stress and temperature, while parameter C depends mainly on stress. A strain dependent damage, defined by the parameter C, causes the accelerating creep stage at stresses lower than 750MPa, whilst its contribution to the creep strain acceleration is less important at higher stresses. The model rationalizes the different behaviors at high and low stress and has been validated with variable stress and temperature creep behavior.展开更多
The current study investigates the behavior of wire electric discharge machining （WEDM） of the super alloy Udimet-L605 by employing sophisticated machine learning approaches. The experimental work was designed on th...The current study investigates the behavior of wire electric discharge machining （WEDM） of the super alloy Udimet-L605 by employing sophisticated machine learning approaches. The experimental work was designed on the basis of the Taguchi orthogonal L27 array, consid- ering six explanatory variables and evaluating their influ- ences on the cutting speed, wire wear ratio （WWR）, and dimensional deviation （DD）. A support vector machine （SVM） algorithm using a normalized poly-kernel and a radial-basis flow kernel is recommended for modeling the wire electric discharge machining process. The grey rela- tional analysis （GRA） approach was utilized to obtain the optimal combination of process variables simultaneously, providing the desirable outcome for the cutting speed, WWR, and DD. Scanning electron microscope and energy dispersive X-ray analyses of the samples were performed for the confirmation of the results. An SVM based on the radial-basis kernel model dominated the normalized poly- kernel model. The optimal combination of process vari- ables for a mutually desirable outcome for the cutting speed, WWR, and DD was determined as Ton1, Toffa, Ip1, WT3, SV1, and WF3. The pulse-on time is the significant variable influencing the cutting speed, WWR, and DD. The largest percentage of copper （8.66%） was observed at the highest cutting speed setting 7.05% of copper at the low of the machine compared to cutting speed setting of the machine.展开更多
文摘Thermal stabilities of microstructure and mechanical property have been investigated on super- alloy U72OLi, which is of great interest of application for jet engine and land-based turbine disc. The results showed that, the primary and secondary γ’?particles maintain good thermal stability at 650 and 7000C with aging time up to 3000 h, while the tertiary γ’?is apparently dependent on aging temperature and time. The tertiary γ’?particles undergo a procedure of coarsening, dissolution and eventually complete disappearance with the increasing of aging time and temper- ature. They exhibit unusual high sensibility upon aging temperature, which is attributed to the lattice misfit between the γ’?precipitates and the matrix in the alloy. The grain boundary phase M23C6 remains stable without forming of sigma phase even with aging time up to 3000 h at 700℃. Microhardness decreases apparently with increasing aging time and aging temperature. Theoretical analysis based on dislocation mechanism indicates that the change of microhardness should be attributed to the evolution of the tertiary γ’?during aging.
文摘Constant load creep tests on isothermally forged Udimet 720Li, an advanced superalloy for gas turbine disc application, were run in the stress/temperature field 900-450MPa/650-700 ℃ producing rupture times in the 20-5000h range. The creep curves have shown a predominant accelerating creep stage, that has been described by the following equation: where ε min depends on stress and temperature, while parameter C depends mainly on stress. A strain dependent damage, defined by the parameter C, causes the accelerating creep stage at stresses lower than 750MPa, whilst its contribution to the creep strain acceleration is less important at higher stresses. The model rationalizes the different behaviors at high and low stress and has been validated with variable stress and temperature creep behavior.
文摘The current study investigates the behavior of wire electric discharge machining （WEDM） of the super alloy Udimet-L605 by employing sophisticated machine learning approaches. The experimental work was designed on the basis of the Taguchi orthogonal L27 array, consid- ering six explanatory variables and evaluating their influ- ences on the cutting speed, wire wear ratio （WWR）, and dimensional deviation （DD）. A support vector machine （SVM） algorithm using a normalized poly-kernel and a radial-basis flow kernel is recommended for modeling the wire electric discharge machining process. The grey rela- tional analysis （GRA） approach was utilized to obtain the optimal combination of process variables simultaneously, providing the desirable outcome for the cutting speed, WWR, and DD. Scanning electron microscope and energy dispersive X-ray analyses of the samples were performed for the confirmation of the results. An SVM based on the radial-basis kernel model dominated the normalized poly- kernel model. The optimal combination of process vari- ables for a mutually desirable outcome for the cutting speed, WWR, and DD was determined as Ton1, Toffa, Ip1, WT3, SV1, and WF3. The pulse-on time is the significant variable influencing the cutting speed, WWR, and DD. The largest percentage of copper （8.66%） was observed at the highest cutting speed setting 7.05% of copper at the low of the machine compared to cutting speed setting of the machine.
