Uniaxial tensile testing explored the Portevin-Le Chatelier(PLC)effect in nickel-based superalloys featuring high Mo/Cr mass ratios,focusing on the influence of variations in the initial microstructure on the deformat...Uniaxial tensile testing explored the Portevin-Le Chatelier(PLC)effect in nickel-based superalloys featuring high Mo/Cr mass ratios,focusing on the influence of variations in the initial microstructure on the deformation behavior at room and elevated temperatures.Experimental results indicated that the PLC effect was observed solely in the high-temperature tensile curves.However,the deformation mechanisms and characteristics of the PLC effect varied with different initial microstructures.Solid solution(SS)and over-aged(OA)samples exhibited C-type serrations,while under-aged(UA)and peak-aged(PA)specimens,featuring short-and long-range ordered phases,respectively,exhibited A+B type serrations in their tensile curves.Microstructural evolution from the SS to the UA,PA and OA states changed their stacking fault energy(SFE),leading to a sequential transformation in the plastic deformation mechanisms during high-temperature tensile deformation:stacking fault(SF)→nanotwin→microtwin→SF.C-type serrations in the SS samples were associated with high solute-atom contents and SF formation.The PLC effects in the UA and PA samples were predominantly caused by solute atom pinning dislocations.Although precipitates and twins were not the primary drivers of the PLC effect,they impeded dislocation migration,exacerbated solute-atom segregation and enhanced dislocation pinning,generating A+B-shaped serrations.In the OA specimens,precipitated phases induced interfacial mismatch under thermal-force coupling.SF shearing of the precipitated phase and subsequent re-dissolution facilitated the formation of C-type serrations,whose PLC effect was induced by the combined action of dynamic strain aging(DSA),SFs of the matrix and diffusion-controlled pseudo-locking mechanisms.展开更多
The Portevin-Le Chatelier(PLC)effect is a plastic instability in alloys at certain strain rates and deformation temperatures.This plastic instability exhibits serrated yielding in the temporal domain and strain locali...The Portevin-Le Chatelier(PLC)effect is a plastic instability in alloys at certain strain rates and deformation temperatures.This plastic instability exhibits serrated yielding in the temporal domain and strain localization in the spatial domain.Wrought Ni-based superalloys often exhibit the PLC effect.To guarantee the safe and stable operation of equipment,it is important to study the PLC effect in wrought Ni-based superalloys.This paper provides a review of various experimental phenomena and micromechanisms related to the PLC effect in wrought Ni-based superalloys,which have been reported in various publications in recent years and include work from our own group.The influences of stacking fault energy andγ’precipitates on the PLC effect in wrought Ni-based superalloys are also discussed in detail.Additionally,several suggestions for the future study of the PLC effect in wrought Ni-based superalloys are provided.展开更多
The Portevin-Le Chatelier （PLC） effect in the Nimonic 263 superalloy was investigated by tensile test at a wide temperature ranges from 293 to 1033 K and strain rates between 0.1 and 6.25 × 10^-6 s-1. Simple bi...The Portevin-Le Chatelier （PLC） effect in the Nimonic 263 superalloy was investigated by tensile test at a wide temperature ranges from 293 to 1033 K and strain rates between 0.1 and 6.25 × 10^-6 s-1. Simple binary alloys Ni- 0.4C, Ni-24Cr and Ni-5（8）Mo were also tested in order to identify which elements were responsible for the PLC effect in the Nimonic 263 alloy. The results demonstrated that for Nimonic 263 alloy, PLC effect occurred at certain temperatures and low strain rates. Normal PLC effect exhibiting type-A and -（A ＋ B） serrations was attributed to the enhanced solute diffusion with increasing temperature, while inverse PLC effect with type-C serration was caused by unlocking process. The activation energy for the normal PLC effect was calculated to be 68 kJ/mol, and diffusion of substitutional solutes such as Cr and Mo was identified to be responsible for the PLC effect. In comparison with the PLC effect in simple binary alloys, solute atmospheres formed by different kinds of atoms in Nimonic 263 alloy work more effectively, increasing locking strength and corresponding mean stress drop magnitude.展开更多
基金supported by Guizhou Provincial Key Technology R&D Program(No.[2022]052).
文摘Uniaxial tensile testing explored the Portevin-Le Chatelier(PLC)effect in nickel-based superalloys featuring high Mo/Cr mass ratios,focusing on the influence of variations in the initial microstructure on the deformation behavior at room and elevated temperatures.Experimental results indicated that the PLC effect was observed solely in the high-temperature tensile curves.However,the deformation mechanisms and characteristics of the PLC effect varied with different initial microstructures.Solid solution(SS)and over-aged(OA)samples exhibited C-type serrations,while under-aged(UA)and peak-aged(PA)specimens,featuring short-and long-range ordered phases,respectively,exhibited A+B type serrations in their tensile curves.Microstructural evolution from the SS to the UA,PA and OA states changed their stacking fault energy(SFE),leading to a sequential transformation in the plastic deformation mechanisms during high-temperature tensile deformation:stacking fault(SF)→nanotwin→microtwin→SF.C-type serrations in the SS samples were associated with high solute-atom contents and SF formation.The PLC effects in the UA and PA samples were predominantly caused by solute atom pinning dislocations.Although precipitates and twins were not the primary drivers of the PLC effect,they impeded dislocation migration,exacerbated solute-atom segregation and enhanced dislocation pinning,generating A+B-shaped serrations.In the OA specimens,precipitated phases induced interfacial mismatch under thermal-force coupling.SF shearing of the precipitated phase and subsequent re-dissolution facilitated the formation of C-type serrations,whose PLC effect was induced by the combined action of dynamic strain aging(DSA),SFs of the matrix and diffusion-controlled pseudo-locking mechanisms.
基金financially supported by the National Natural Science Foundation of China(Nos.51671189 and 51271174)the Ministry of Science and Technology of China(Nos.2017YFA0700703 and 2019YFA0705304)。
文摘The Portevin-Le Chatelier(PLC)effect is a plastic instability in alloys at certain strain rates and deformation temperatures.This plastic instability exhibits serrated yielding in the temporal domain and strain localization in the spatial domain.Wrought Ni-based superalloys often exhibit the PLC effect.To guarantee the safe and stable operation of equipment,it is important to study the PLC effect in wrought Ni-based superalloys.This paper provides a review of various experimental phenomena and micromechanisms related to the PLC effect in wrought Ni-based superalloys,which have been reported in various publications in recent years and include work from our own group.The influences of stacking fault energy andγ’precipitates on the PLC effect in wrought Ni-based superalloys are also discussed in detail.Additionally,several suggestions for the future study of the PLC effect in wrought Ni-based superalloys are provided.
基金financially supported by‘‘Hundreds of Talents Project’’National Basic Research Program of China(No.2010CB631206)(Nos.51171179,51128101 and 51271174)
文摘The Portevin-Le Chatelier （PLC） effect in the Nimonic 263 superalloy was investigated by tensile test at a wide temperature ranges from 293 to 1033 K and strain rates between 0.1 and 6.25 × 10^-6 s-1. Simple binary alloys Ni- 0.4C, Ni-24Cr and Ni-5（8）Mo were also tested in order to identify which elements were responsible for the PLC effect in the Nimonic 263 alloy. The results demonstrated that for Nimonic 263 alloy, PLC effect occurred at certain temperatures and low strain rates. Normal PLC effect exhibiting type-A and -（A ＋ B） serrations was attributed to the enhanced solute diffusion with increasing temperature, while inverse PLC effect with type-C serration was caused by unlocking process. The activation energy for the normal PLC effect was calculated to be 68 kJ/mol, and diffusion of substitutional solutes such as Cr and Mo was identified to be responsible for the PLC effect. In comparison with the PLC effect in simple binary alloys, solute atmospheres formed by different kinds of atoms in Nimonic 263 alloy work more effectively, increasing locking strength and corresponding mean stress drop magnitude.
