Article
Materials Science, Multidisciplinary
Yan Peng, Shuo Guo, Caiyi Liu, Silvia Barella, Shicheng Liang, Andrea Gruttadauria, Carlo Mapelli
Summary: This paper investigates the DRX behavior of low carbon steel, revealing the effect of temperature and strain rate on DRX through hot compression tests and a established kinetic model. Additionally, the DRX behavior during hot rolling is simulated, and it is found that the non-uniform distribution of DRX is related to high-temperature deformation.
JOURNAL OF MATERIALS RESEARCH AND TECHNOLOGY-JMR&T
(2022)
Article
Materials Science, Multidisciplinary
Guowang Liu, Chunliang Mao, Ran Ding, Liming Yu, Chenxi Liu, Yongchang Liu
Summary: The study investigates the DRX behavior of austenite in reduced activation ferritic/martensitic steel through isothermal compression tests and constitutive modelling. Flow stress and softening behavior are found to be influenced by deformation temperature and strain rate. A new recrystallization kinetics model is developed to understand the relationship between recrystallization volume fraction and grain size during hot deformation, providing insights for controlling grain size in industrial processes.
JOURNAL OF NUCLEAR MATERIALS
(2021)
Article
Chemistry, Physical
Dahai Liu, Haorui Chai, Liang Yang, Wenqing Qiu, Zhenghua Guo, Zhilu Wang
Summary: This paper studied the flow stress behavior and recrystallization mechanism of GH5188 superalloy, finding dynamic recrystallization to be the main softening mechanism. EBSD results indicated different recrystallization mechanisms at different temperatures, and twinning played a key role in subgrain refinement at high strain rates.
JOURNAL OF ALLOYS AND COMPOUNDS
(2022)
Article
Materials Science, Multidisciplinary
Yahui Han, Changsheng Li, Jinyi Ren, Chunlin Qiu, Shuaishuai Chen, En Li
Summary: The study investigated the dynamic recrystallization behavior of as-cast 4Cr5MoSiV1 steel through hot compression tests conducted at different temperatures and strain rates. It was found that the nucleation of DRX was mainly performed by bulging and sub-grain swallowing, and the presence of dendrite segregation had a significant impact on DRX.
JOURNAL OF MATERIALS SCIENCE
(2021)
Article
Materials Science, Multidisciplinary
Xiaoyun Sun, Banglun Wang, Yuanpei Duan, Qi Liu, Xiang Xu, Sheng Wang, Xianfeng Yang, Xue Feng
Summary: The dynamic recrystallization behavior and microstructure evolution of medium-Mn steel were investigated through isothermal hot compression tests. Constitutive equations and a grain size evolution model were established based on flow stress-strain curves and microstructure analysis. The accuracy of the model was confirmed with high predictive ability and low average absolute relative error.
JOURNAL OF MATERIALS RESEARCH AND TECHNOLOGY-JMR&T
(2023)
Article
Chemistry, Physical
Yanbin Pei, Xuanhui Qu, Qilu Ge, Tiejun Wang
Summary: The study investigated the hot deformation characteristics and mechanisms of borated stainless steel specimens prepared by hot isostatic pressing, revealing that the boron-containing phase prevented dynamic recrystallization. Additionally, it was found that hot deformation promoted the generation of borides and led to the inhomogeneous distribution of elements in the boron-containing phase.
Editorial Material
Materials Science, Multidisciplinary
Chang-an Li, Guoliang Qin, Hao Wang, Peihao Geng
Summary: This paper conducted hot compression experiments to analyze the deformation behavior and dynamic recrystallization of FGH96 at high temperature and strain rate conditions. Two strain modified viscoplastic constitutive models were established and proven to accurately reflect the deformation behavior and suitable for numerical simulation of IFW.
JOURNAL OF MATERIALS RESEARCH AND TECHNOLOGY-JMR&T
(2022)
Article
Materials Science, Multidisciplinary
Liping Zhong, Bo Wang, Chundong Hu, Jieyu Zhang, Yu Yao
Summary: The study aimed to improve the microstructure uniformity of an ultra-high strength martensitic steel through experimental and simulation research. By establishing suitable process parameters and models, the research provided insights into obtaining forging stock with a uniform and refinement microstructure, which is essential for formulating appropriate forging processes.
Article
Chemistry, Physical
Xuewen Chen, Bingqi Liu, Bo Zhang, Jiawei Sun, Zhen Yang, Xudong Zhou, Tao Huang, Danqing Yin
Summary: A dynamic recrystallization model of Cr8 alloy steel was established, and its reliability was verified through software simulation. Experimental results showed that the model could effectively predict the dynamic recrystallization of Cr8 alloy steel.
Review
Materials Science, Multidisciplinary
Hamed Aghajani Derazkola, Eduardo Garcia, Alberto Murillo-Marrod, Aintzane Conde Fernandez
Summary: This review paper presents the latest developments in the numerical analysis, microstructural simulation, and artificial intelligence methods for the hot deformation process of martensitic stainless steels (MSS). Modeling and simulation analysis can reduce the number of experiments and provide insights into the effects of strain and strain rate variations in manufacturing processes.
JOURNAL OF MATERIALS RESEARCH AND TECHNOLOGY-JMR&T
(2022)
Article
Materials Science, Multidisciplinary
X. W. Duan, J. J. Liu, B. Gong, P. Li, J. S. Liu
Summary: This study investigated the dynamic recrystallization behavior of a high-strength steel through hot compression tests and established DRX kinetic and grain size models. A rigid-plastic finite element simulation was built to analyze microstructural behavior during uniaxial hot compression. The simulation results were in good agreement with experimental data, providing theoretical guidance and process optimization for metal forming processes.
METALS AND MATERIALS INTERNATIONAL
(2021)
Article
Materials Science, Multidisciplinary
Lin Wang, Chen Chen, Zhuyu Wang, Zhuoyuan Li, Bo Lv, Fucheng Zhang
Summary: Super austenitic stainless steel (SASS) exhibits different dynamic recrystallization (DRX) mechanisms under different temperature and strain rate conditions. At lower temperatures or strain rates, partial formation of DRX grains occurs through the development of low-angle to high-angle grain boundaries; while at higher temperatures or strain rates, the main DRX mechanism is the formation of DRX grains through sub-grain rotation.
MATERIALS SCIENCE AND TECHNOLOGY
(2022)
Article
Metallurgy & Metallurgical Engineering
Ignacio Alcelay, Esteban Pena, Anas Al Omar
Summary: The hot working behavior of medium carbon duplex cast steel was studied using uniaxial hot compression tests, constructing processing maps to optimize the hot workability of the material. The results showed safe domains associated with dynamic recrystallization and dynamic recovery, as well as an unsafe domain related to plastic deformation instabilities.
INTERNATIONAL JOURNAL OF MATERIALS RESEARCH
(2021)
Article
Materials Science, Multidisciplinary
B. Sulkowski, R. Chulist
Summary: The effect of texture on alloy properties and the evolution of texture during hot extrusion of Mg were studied through experiments and simulations. A model based on a viscoplastic formulation was extended to a cellular automaton procedure to consider recrystallization mechanisms. The main textural components were identified for each deformation temperature and a mechanism for their formation was proposed.
MATERIALS CHARACTERIZATION
(2023)
Article
Crystallography
Huaying Li, Lihong Gao, Yaohui Song, Lidong Ma, Haitao Liu, Juan Li, Guanghui Zhao
Summary: The study on the thermal compression simulation of antibacterial stainless steel containing copper revealed that the dynamic recrystallization mechanism is discontinuous, while the growth of twins relies on recrystallization. An Arrhenius model considering strain compensation was established for flow stress, achieving high accuracy with a correlation coefficient of 0.979 and an average relative absolute error of 7.066%.
Article
Nanoscience & Nanotechnology
M. H. Asoushe, A. Zarei Hanzaki, H. R. Abedi, B. Mirshekari, T. Wegener, S. Sajadifar, T. Niendorf
Summary: The microstructural and textural evolutions of as-cast high entropy alloy were investigated during thermomechanical processing at temperatures ranging from 25 to 500 degrees Celsius. The alloy exhibited significant strength-ductility ratio at room temperature and maintained mechanical stability at elevated temperatures. The volume fractions of constituent phases and the texture of the alloy were found to be consistent across different deformation temperatures.
MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING
(2021)
Article
Materials Science, Multidisciplinary
S. Picak, T. Wegener, S. Sajadifar, C. Sobrero, J. Richter, H. Kim, T. Niendorf, I Karaman
Summary: In this study, the yield strength of High Entropy Alloy CoCrFeMnNi was improved through Equal Channel Angular Pressing (ECAP), resulting in very high yield strength levels and superior fatigue life at low strain amplitudes. The refined grain size, high density dislocation walls, and dislocation annihilation were identified as key factors governing the fatigue life and hardening behavior of the alloy.
Article
Materials Science, Multidisciplinary
Seyed Vahid Sajadifar, Ali Hosseinzadeh, Julia Richter, Marcel Krochmal, Thomas Wegener, Artjom Bolender, Akbar Heidarzadeh, Thomas Niendorf, Guney Guven Yapici
Summary: This study investigates the novel combination of friction stir processing (FSP) and additive manufacturing (AM) for the improvement of the mechanical properties of 316 L stainless steel. It is found that FSP can effectively refine the microstructure, resulting in enhanced hardness, yield point, and ultimate strength. The improvement is attributed to the structural refinement and densification of the material.
ADVANCED ENGINEERING MATERIALS
(2022)
Article
Engineering, Mechanical
S. V. Sajadifar, E. Scharifi, T. Wegener, M. Krochmal, S. Lotz, K. Steinhoff, T. Niendorf
Summary: This study evaluated the mechanical properties of thermo-mechanically processed AA6082 and AA7075 sheets under cyclic loading through low-cycle fatigue experiments. Different cooling rates resulted in precipitates with varying sizes and morphologies. The specimens processed in tools with temperatures of 24°C and 200°C exhibited superior mechanical properties, while different behavior was observed for the specimens formed in the tool with a temperature of 350°C. Thorough analysis of microstructural features revealed the significant impact of thermal history on the final performance of high-strength aluminum alloys.
INTERNATIONAL JOURNAL OF FATIGUE
(2022)
Article
Crystallography
Jens Decke, Anna Engelhardt, Lukas Rauch, Sebastian Degener, Seyed Vahid Sajadifar, Emad Scharifi, Kurt Steinhoff, Thomas Niendorf, Bernhard Sick
Summary: This study focuses on predicting the hot deformation behavior of thermo-mechanically processed precipitation hardenable aluminum alloy AA7075. Isothermal uniaxial tensile tests were conducted on different material conditions, and a comparative study was performed between machine learning modeling techniques and the Zerilli-Armstrong model. The results show that machine learning methods outperformed the Z-A model, with extreme Gradient Boosting model yielding the highest error reduction.
Article
Materials Science, Multidisciplinary
Guney Guven Yapici, Seyed Vahid Sajadifar, Ali Hosseinzadeh, Thomas Wegener, Cesar Sobrero, Anna Engelhardt, Thomas Niendorf
Summary: In this study, the cyclic mechanical behavior of AZ31 magnesium alloy after multipass friction stir processing (FSP) is investigated up to the very high-cycle fatigue (VHCF) regime. The grain refinement and texture evolution after processing are evaluated to enhance the understanding of the fatigue response. The friction stir processed AZ31 shows increased ultimate tensile strength and ductility, but its fatigue performance deteriorates due to low yield strength and texture evolution after processing.
ADVANCED ENGINEERING MATERIALS
(2023)
Article
Materials Science, Multidisciplinary
M. Krochmal, A. Nammalvar Raja Rajan, G. Moeini, S. V. Sajadifar, T. Wegener, T. Niendorf
Summary: Welding and joining of hybrid components, consisting of additively manufactured (AM) parts and conventionally processed parts, can be achieved with the friction stir welding (FSW) process. The strength of dissimilar welded joints is influenced by the original casting material. Cast materials perform slightly better than hybrid AM-cast materials in fatigue testing, possibly due to more pronounced strain inhomogeneities in the hybrid materials. FSW can be used to fabricate large parts with cost reduction, by placing the AM as-built material in the region requiring superior cyclic load-bearing capacity.
JOURNAL OF MATERIALS RESEARCH
(2023)
Article
Materials Science, Multidisciplinary
S. Sajadifar, T. Suckow, B. Heider, M. Oechsner, P. Groche, T. Niendorf
Summary: This study investigated the effects of solution heat treatment parameters and quench media on the microstructure, mechanical and corrosion properties of roll-formed EN AW 7075 alloy. The results showed that water quenching achieved the highest yield stress and ultimate tensile strength, while air cooling led to inferior mechanical properties. Corrosion tests revealed that the cooling rate significantly influenced the corrosion resistance of the alloy. It was also found that using quenching nozzles could achieve a high cooling rate similar to water quenching.
MATERIALWISSENSCHAFT UND WERKSTOFFTECHNIK
(2022)
Article
Crystallography
Seyed Vahid Sajadifar, Hans Juergen Maier, Thomas Niendorf, Guney Guven Yapici
Summary: The elevated-temperature deformation characteristics and microstructural evolution of a Ti-5V-5Mo-5Cr-4Al alloy were studied under solution-treatment conditions. The dominant softening mechanism was found to be dynamic recovery (DRV), with dynamic precipitation (DPN) occurring only at specific strain rates and temperatures. Void coalescence was observed with increasing deformation temperature and decreasing strain rate. These findings provide insights for the processing of this novel beta titanium alloy.
Article
Engineering, Manufacturing
Seyed Vahid Sajadifar, Timon Suckow, Caroline Karina Chandra, Ben Heider, Akbar Heidarzadeh, Janez Zavasnik, Ruediger Reitz, Matthias Oechsner, Peter Groche, Thomas Niendorf
Summary: The impacts of different thermo-mechanical process routes on the mechanical properties, microstructure, and corrosion resistance of EN AW 7075 alloy were investigated. The focus was on a simulated forming process under two different conditions, T6 and W-Temper. Regardless of soaking time and pre-deformation, specimens quenched in water showed better mechanical properties compared to air-cooled ones. However, a shorter solution heat-treatment soaking time in the pre-deformed condition caused a decrease in elongation at fracture. Microstructural analysis revealed a high fraction of fine eta' strengthening precipitates in the specimens quenched in water, regardless of pre-deformation and soaking time.
JOURNAL OF MANUFACTURING PROCESSES
(2023)
Article
Materials Science, Multidisciplinary
Seyed Vahid Sajadifar, Philipp Krooss, Marcel Krochmal, Thomas Wegener, Akbar Heidarzadeh, Hannes Froeck, Janez Zavasnik, Olaf Kessler, Thomas Niendorf
Summary: This study presents the effects of aging under superimposed external stress on the fatigue performance and microstructural evolution of a high-strength aluminum alloy (EN AW-7075). The combination of heat treatment and external stress, known as stress aging, accelerates the precipitation kinetics and promotes the formation and growth of strengthening precipitates. The stress aging process also reduces the dimensions of precipitate-free zones near grain boundaries. Furthermore, stress aging enhances the monotonic mechanical properties of EN AW-7075 without degrading the cyclic performance in the low-cycle fatigue regime.
ADVANCED ENGINEERING MATERIALS
(2023)
Article
Materials Science, Multidisciplinary
Ezgi Buetev Oecal, Seyed Vahid Sajadifar, Erik P. K. Sellner, Malte Vollmer, Akbar Heidarzadeh, Janez Zavasnik, Thomas Niendorf, Peter Groche
Summary: In this study, functionally graded AA7075 components manufactured via hot stamping are investigated, with a focus on the effect of different process variables on localized microstructure evolution. The design of experiments allows for the assessment of transfer time, quenching time, and quenching media. Mechanical properties are evaluated through hardness and tensile tests. The results show that sections formed in the cooled part of the tool have higher mechanical strength and the formation of fine precipitates, while sections formed in the heated part exhibit higher ductility and the formation of coarse precipitates.
ADVANCED ENGINEERING MATERIALS
(2023)
Article
Materials Science, Multidisciplinary
Seyed Vahid Sajadifar, Joerg Baumgartner, Marcel Krochmal, Andreas Maciolek, Marcus Klein, Moritz Roesser, Markus Grass, Hannes Froeck, Martin Fehlbier, Olaf Kessler, Stefan Boehm, Matthias Oechsner, Tobias Melz, Thomas Niendorf
Summary: The monotonic and cyclic properties of a novel Al-Mg-Zn-Cu-Si compositionally complex alloy (CCA) are investigated. Microstructural studies reveal the presence of a eutectic phase and fishbone-type structures embedded in the Al-matrix. The alloy shows promising mechanical properties under compressive loading, but exhibits low ultimate strength and brittle behavior under tension, as well as poor fatigue performance in the low-cycle fatigue (LCF) regime. The presence of brittle intermetallic phases and shrinkage defects are responsible for the poor tensile properties and inferior LCF behavior, despite homogenization treatments leading to spheroidization of all coarse precipitates.
ADVANCED ENGINEERING MATERIALS
(2023)
Article
Engineering, Mechanical
Amin Radi, Seyedvahid Sajadifar, S. Vegar Seyedmohammadi, Marcel Krochmal, Artjom Bolender, Thomas Wegener, Thomas Niendorf, Guney Guven Yapici
Summary: In this study, a multi-phase non-equiatomic FeCrNiMnCo high entropy alloy (HEA) was fabricated through vacuum induction melting. Thermo-mechanical treatments consisting of cold rolling and annealing were used to improve the mechanical properties of the alloy. Tensile experiments showed that the yield strength and ultimate tensile strength levels of the HEA can be significantly enhanced by the thermo-mechanical processing. Similarly, strain-controlled low-cycle fatigue experiments revealed that the processed samples had higher stress levels and fatigue lives compared to the as-received counterpart.
INTERNATIONAL JOURNAL OF FATIGUE
(2023)
Article
Engineering, Mechanical
A. Maciolek, A. Joeckel, S. Voelkers, M. Hatzky, T. Suckow, L. Schell, S. V. Sajadifar, T. Wegener, B. Moeller, J. Baumgartner, T. Melz, S. Boehm, P. Groche, T. Niendorf
Summary: Zinc-containing aluminum alloys of the 7xxx series have the potential for lightweight applications due to their high strength and low density. Friction stir welding (FSW) has been shown to produce joints with excellent properties. Post-weld heat treatment (PWHT) can further improve the alloy's strength through precipitation hardening. However, PWHT can also lead to reduced fatigue strength, which can be improved by removing the surface layer.
INTERNATIONAL JOURNAL OF FATIGUE
(2024)
