Doctorat Erasmus Mundus en Ciència i Enginyeria de Materials Avançats
http://hdl.handle.net/2117/184591
2024-03-29T04:44:34ZAnalysis of strain-induced precipitates by delta-processing in Inconel 718 superalloy
http://hdl.handle.net/2117/344809
Analysis of strain-induced precipitates by delta-processing in Inconel 718 superalloy
Páramo-Kañetas, Pedro; Ozturk, Utkudeniz; Calvo Muñoz, Jessica; Guerrero Mata, Martha P.; Cabrera Marrero, José M.
Delta-Processing (DP) is a suitable heat treatment process aiming at controlling grain growth during hot deformation of the well-known Ni-base superalloy Inconel 718 (IN718). DP is often applied by heating up to 900 °C for 24 h in order to promote d-phase saturation prior to deformation. In addition to the d-phase, Mo and Cr-rich carbides in the form of M23C6 may also precipitate during the subsequent hot deformation of this alloy in the range of 950–1000 °C These carbides are induced by deformation and can affect the static and dynamic recrystallization of the matrix.
The objective of the current work is to understand the precipitation of M23C6 carbides when the material has been saturated with d-phase precipitation, as well as their interaction with recrystallization phenomena. For this purpose, a series of double-strain hot compression test (double-hit) were carried out. Several holding times were applied between the first and the second hit in order to derive the softening/hardening fraction progress with time. Microstructural characterization of the samples was performed through Scanning Electron Microscopy (SEM) and X-ray diffraction (XRD) in order to identify the precipitating/dissolving phases under each testing condition.Delta-Processing (DP) is a suitable heat treatment process aiming at controlling grain growth during hot deformation of the well-known Ni-base superalloy Inconel 718 (IN718). DP is often applied by heating up to 900 °C for 24 h in order to promote d-phase saturation prior to deformation. In addition to the d-phase, Mo and Cr-rich carbides in the form of M23C6 may also precipitate during the subsequent hot deformation of this alloy in the range of 950–1000 °C These carbides are induced by deformation and can affect the static and dynamic recrystallization of the matrix.
The objective of the current work is to understand the precipitation of M23C6 carbides when the material has been saturated with d-phase precipitation, as well as their interaction with recrystallization phenomena. For this purpose, a series of double-strain hot compression test (double-hit) were carried out. Several holding times were applied between the first and the second hit in order to derive the softening/hardening fraction progress with time. Microstructural characterization of the samples was performed through Scanning Electron Microscopy (SEM) and X-ray diffraction (XRD) in order to identify the precipitating/dissolving phases under each testing condition.
2021-04-29T11:39:17ZPáramo-Kañetas, PedroOzturk, UtkudenizCalvo Muñoz, JessicaGuerrero Mata, Martha P.Cabrera Marrero, José M.Delta-Processing (DP) is a suitable heat treatment process aiming at controlling grain growth during hot deformation of the well-known Ni-base superalloy Inconel 718 (IN718). DP is often applied by heating up to 900 °C for 24 h in order to promote d-phase saturation prior to deformation. In addition to the d-phase, Mo and Cr-rich carbides in the form of M23C6 may also precipitate during the subsequent hot deformation of this alloy in the range of 950–1000 °C These carbides are induced by deformation and can affect the static and dynamic recrystallization of the matrix.
The objective of the current work is to understand the precipitation of M23C6 carbides when the material has been saturated with d-phase precipitation, as well as their interaction with recrystallization phenomena. For this purpose, a series of double-strain hot compression test (double-hit) were carried out. Several holding times were applied between the first and the second hit in order to derive the softening/hardening fraction progress with time. Microstructural characterization of the samples was performed through Scanning Electron Microscopy (SEM) and X-ray diffraction (XRD) in order to identify the precipitating/dissolving phases under each testing condition.Delta-Processing (DP) is a suitable heat treatment process aiming at controlling grain growth during hot deformation of the well-known Ni-base superalloy Inconel 718 (IN718). DP is often applied by heating up to 900 °C for 24 h in order to promote d-phase saturation prior to deformation. In addition to the d-phase, Mo and Cr-rich carbides in the form of M23C6 may also precipitate during the subsequent hot deformation of this alloy in the range of 950–1000 °C These carbides are induced by deformation and can affect the static and dynamic recrystallization of the matrix.
The objective of the current work is to understand the precipitation of M23C6 carbides when the material has been saturated with d-phase precipitation, as well as their interaction with recrystallization phenomena. For this purpose, a series of double-strain hot compression test (double-hit) were carried out. Several holding times were applied between the first and the second hit in order to derive the softening/hardening fraction progress with time. Microstructural characterization of the samples was performed through Scanning Electron Microscopy (SEM) and X-ray diffraction (XRD) in order to identify the precipitating/dissolving phases under each testing condition.Effect of chitin nanocrystals on crystallization and properties of poly(lactic acid)-based nanocomposites
http://hdl.handle.net/2117/340883
Effect of chitin nanocrystals on crystallization and properties of poly(lactic acid)-based nanocomposites
Singh, Shikha; Maspoch Rulduà, M. Lluïsa
The crystalline phase of poly(lactic acid) (PLA) has crucial effects on its own properties and nanocomposites. In this study, the isothermal crystallization of PLA, triethyl citrate-plasticized PLA (PLA–TEC), and its nanocomposite with chitin nanocrystals (PLA–TEC–ChNC) at different temperatures and times was investigated, and the resulting properties of the materials were characterized. Both PLA and PLA–TEC showed extremely low crystallinity at isothermal temperatures of 135, 130, 125 °C and times of 5 or 15 min. In contrast, the addition of 1 wt % of ChNCs significantly improved the crystallinity of PLA under the same conditions owing to the nucleation effect of the ChNCs. The samples were also crystallized at 110 °C to reach their maximal crystallinity, and PLA–TEC–ChNC achieved 48% crystallinity within 5 min, while PLA and PLA–TEC required 40 min to reach a similar level. Moreover, X-ray diffraction analysis showed that the addition of ChNCs resulted in smaller crystallite sizes, which further influenced the barrier properties and hydrolytic degradation of the PLA. The nanocomposites had considerably lower barrier properties and underwent faster degradation compared to PLA–TEC110. These results confirm that the addition of ChNCs in PLA leads to promising properties for packaging applications.
2021-03-03T15:30:50ZSingh, ShikhaMaspoch Rulduà, M. LluïsaThe crystalline phase of poly(lactic acid) (PLA) has crucial effects on its own properties and nanocomposites. In this study, the isothermal crystallization of PLA, triethyl citrate-plasticized PLA (PLA–TEC), and its nanocomposite with chitin nanocrystals (PLA–TEC–ChNC) at different temperatures and times was investigated, and the resulting properties of the materials were characterized. Both PLA and PLA–TEC showed extremely low crystallinity at isothermal temperatures of 135, 130, 125 °C and times of 5 or 15 min. In contrast, the addition of 1 wt % of ChNCs significantly improved the crystallinity of PLA under the same conditions owing to the nucleation effect of the ChNCs. The samples were also crystallized at 110 °C to reach their maximal crystallinity, and PLA–TEC–ChNC achieved 48% crystallinity within 5 min, while PLA and PLA–TEC required 40 min to reach a similar level. Moreover, X-ray diffraction analysis showed that the addition of ChNCs resulted in smaller crystallite sizes, which further influenced the barrier properties and hydrolytic degradation of the PLA. The nanocomposites had considerably lower barrier properties and underwent faster degradation compared to PLA–TEC110. These results confirm that the addition of ChNCs in PLA leads to promising properties for packaging applications.High-temperature deformation behavior of 718PLUs: Consideration of y' effects
http://hdl.handle.net/2117/188270
High-temperature deformation behavior of 718PLUs: Consideration of y' effects
Ozturk, Utkudeniz; Cabrera Marrero, José M.; Calvo Muñoz, Jessica; Redjaïmia, Abdelkrim; Ghanbaja, Jaâfar
The hot deformation behavior of 718Plus is modeled through a physically based hybrid dislocation density model, which includes the effects of precipitating particles. It is well known that the service performance and hot flow characteristics of this alloy are strongly dependent on the microstructure, particularly the grain size and second-phase particles. Thus, comprehension and modeling of the hot flow behavior is an important task. In precipitation hardening alloys (superalloys, microalloyed steels, etc.), it is particularly challenging to model the microstructural evolution in the processing windows, where material softening and precipitation processes take place concurrently. In this work, the initial stages of the deformation are studied. A model based on dislocation density evolution is presented. As in conventional approaches, the dislocation density is considered as a competition between dislocation generation and dynamic recovery at the early stages of deformation. Recovery is assumed to be driven by glide and climb of dislocations, which are considered to be proportional to the strain rate and damped by the existence of second-phase particles. It is known that under high-temperature deformation conditions, 718Plus may undergo dynamic precipitation. Second-phase particles in the material may impede the grain boundary motion and contribute to an increase in flow stress. To account for the dynamic precipitation, the present model combines experimental results and precipitation models to predict volume fraction and particle size. The effect of aging is studied through transmission electron microscopy (TEM) characterization of the specimens from interrupted tests at the onset of dynamic recrystallization. Stress contribution due to different modes of dislocation precipitation interaction are modeled and integrated to the phenomenological dislocation density–based hardening models.
2020-05-20T12:22:25ZOzturk, UtkudenizCabrera Marrero, José M.Calvo Muñoz, JessicaRedjaïmia, AbdelkrimGhanbaja, JaâfarThe hot deformation behavior of 718Plus is modeled through a physically based hybrid dislocation density model, which includes the effects of precipitating particles. It is well known that the service performance and hot flow characteristics of this alloy are strongly dependent on the microstructure, particularly the grain size and second-phase particles. Thus, comprehension and modeling of the hot flow behavior is an important task. In precipitation hardening alloys (superalloys, microalloyed steels, etc.), it is particularly challenging to model the microstructural evolution in the processing windows, where material softening and precipitation processes take place concurrently. In this work, the initial stages of the deformation are studied. A model based on dislocation density evolution is presented. As in conventional approaches, the dislocation density is considered as a competition between dislocation generation and dynamic recovery at the early stages of deformation. Recovery is assumed to be driven by glide and climb of dislocations, which are considered to be proportional to the strain rate and damped by the existence of second-phase particles. It is known that under high-temperature deformation conditions, 718Plus may undergo dynamic precipitation. Second-phase particles in the material may impede the grain boundary motion and contribute to an increase in flow stress. To account for the dynamic precipitation, the present model combines experimental results and precipitation models to predict volume fraction and particle size. The effect of aging is studied through transmission electron microscopy (TEM) characterization of the specimens from interrupted tests at the onset of dynamic recrystallization. Stress contribution due to different modes of dislocation precipitation interaction are modeled and integrated to the phenomenological dislocation density–based hardening models.