Article
Materials Science, Multidisciplinary
Rong Fu, Yuanchun Huang, Yu Liu, Hui Li
Summary: The thermal deformation behavior of homogenized 2195 Al-Li alloy was investigated under different deformation temperatures and strain rates. It was observed that the flow stress decreases with decreasing strain rate or increasing temperature. The decrease in flow stress at lower temperatures was attributed to the hindering effect of dynamic precipitation of fine secondary phases, which restrict the movement of dislocations and (sub)grain boundaries. Flow localization regions were also observed at specific microstructure conditions. Additionally, DRX and DRV were found to increase with decreasing lnZ values, and the dominant DRX mechanism varied with lnZ values.
METALS AND MATERIALS INTERNATIONAL
(2023)
Article
Materials Science, Multidisciplinary
Hao Shiming, Liu Pengru, Xie Jingpei
Summary: The present study investigates the hot deformation of 35%SiCp/2024Al composite using Gleeble-1500D thermo-mechanical simulators. It is found that the flow stress, microstructure evolution, and deformation mechanism are sensitive to deformation parameters, which can be represented by the Zener-Hollomon parameter (Z) in the hyperbolic sine equation. The softening mechanism, degree of dynamic recrystallization, average grain size, size of precipitates, dislocation density, and nucleation mechanism of dynamic recrystallization are influenced by the Z parameter, and the interaction laws are obtained through analysis.
JOURNAL OF MATERIALS RESEARCH AND TECHNOLOGY-JMR&T
(2023)
Article
Metallurgy & Metallurgical Engineering
Li Ze-cheng, Deng Yun-lai, Yuan Man-fa, Zhang Jin, Guo Xiao-bin
Summary: The study on Al-Mg-Si alloy deformation process shows that dislocation density and energy storage are linearly related to lnZ, indicating continuous recrystallization occurs. It was found that subgrains have good stability during subsequent heat treatment, as dislocations distribute along low angle grain boundaries.
JOURNAL OF CENTRAL SOUTH UNIVERSITY
(2021)
Article
Materials Science, Multidisciplinary
Chun-Nan Lin, Yu-Chih Tzeng, Sheng-Long Lee, An-Hung Tan, Yiin-Kuen Fuh, Aneta Lukaszek-So Lek, Chao-Yu Lin
Summary: Isothermal compression tests were conducted on as-extruded 7005 aluminum alloy to investigate the deformation characteristics and thermal softening mechanisms. The strain distribution and microstructure evolution were simulated using QFormUK. The relationship between lnZ value and microstructure evolution was studied, and lnZ was found to be an effective parameter for investigating microstructures in uniform deformation zones.
MATERIALS TODAY COMMUNICATIONS
(2023)
Article
Chemistry, Physical
Gang Tan, Hui-Zhong Li, Yan Wang, Shi-Chang Qiao, Lei Yang, Zheng-Qin Huang, Tian-Wei Cheng, Zi-Xuan Zhao
Summary: The microstructure evolution of a hot extrusion powder metallurgy nickel-based superalloy was investigated by hot compression tests, showing that the Z parameter has an impact on the nucleation mechanisms of dynamic recrystallization.
JOURNAL OF ALLOYS AND COMPOUNDS
(2021)
Article
Chemistry, Physical
Liudmila Radionova, Danil Perevozchikov, Aleksandr N. Makoveckii, Victor N. Eremin, Alexander M. Akhmedyanov, Sergey Rushchits
Summary: This study investigates the hot deformation behavior of austenitic Ti-modified AISI 321 steel. The experimental results show that the flow stress increases with decreasing deformation temperature and increasing strain rate. At high temperatures and low strain rates, the hot deformation is accompanied by dynamic recrystallization. By analyzing the experimental data, a constitutive equation is established which describes the relationship between flow stress and deformation parameters. The critical strain and the size of recrystallized grains are found to depend on the Zener-Hollomon parameter. It is also discovered that dynamic recrystallization is abruptly suppressed when the Zener-Hollomon parameter exceeds a certain value, possibly due to the presence of titanium carbonitrides.
Article
Materials Science, Multidisciplinary
Jeyong Yu, In Yong Moon, Hi Won Jeong, Ho Won Lee, Ji Hoon Kim, Seong-Hoon Kang
Summary: The study analyzed the effect of activation energy on stress-strain curves by conducting uniaxial compression tests and establishing constitutive modeling based on Zener-Hollomon parameters. Different models were compared for flow stresses and their accuracies were evaluated using average absolute relative error, followed by modeling of dynamic recrystallization behavior. The prediction of material microstructure was successfully achieved.
METALS AND MATERIALS INTERNATIONAL
(2022)
Article
Mechanics
Xiaoshan Xu, Gongxing Yan
Summary: The effect of different parameters of friction stir processing (FSP) on the microstructure and mechanical properties of pure copper were investigated numerically and experimentally. The results showed that by increasing the rotation speed, the grain size increased, and the mechanical properties were improved due to grain refinement.
MECHANICS BASED DESIGN OF STRUCTURES AND MACHINES
(2023)
Article
Metallurgy & Metallurgical Engineering
Bo Wu, Jianbo Li, Lizi Liu, Xianhua Chen, Jun Tan, Jiangfeng Song, Muhammad Rashad, Fusheng Pan
Summary: The high-temperature compressive deformation behaviors of Mg-6Zn-1.5Y-0.5Ce-0.4Zr alloy were investigated, showing three different work hardening stages influenced by the rare earth phase content. The process involves dislocation aggregation, dynamic recovery, and recrystallization. The occurrence of dynamic recrystallization is related to the Zener-Hollomon parameter.
ACTA METALLURGICA SINICA-ENGLISH LETTERS
(2021)
Article
Materials Science, Multidisciplinary
Rui Luo, Yiming Zhou, Pei Gao, Tian Liu, Yu Cao, Hengnan Ding, Wei Lin, Qingtao Liu, Tian Tian
Summary: This paper takes the hot deformation of IN617B as an example and establishes the activation energy, Zener-Hollomon parameter, and hot processing map through hot compression tests. It is found that the high power dissipation area does not completely match the complete dynamic recrystallization area, but the microstructure corresponding to the high power dissipation area and low Z and Q area exhibits higher dynamic recrystallization ability.
JOURNAL OF MATERIALS RESEARCH AND TECHNOLOGY-JMR&T
(2023)
Article
Chemistry, Physical
Ahmed A. Tiamiyu, Edward L. Pang, Xi Chen, James M. LeBeau, Keith A. Nelson, Christopher A. Schuh
Summary: Nanotwinning-assisted dynamic recrystallization is shown to facilitate grain refinement to the nanoscale at high strains and strain rates, providing a pathway to the finest nanocrystalline grain sizes through extreme straining processes.
Article
Materials Science, Multidisciplinary
Jun Xing, Hanlin Ding, Guohui Zhu, Fan Li, Junliang Li
Summary: This paper focuses on the critical strain for dynamic recrystallization (DRX) in designing rolling schedules for the refinement of grain size by boundary-induced transformation mechanisms. A novel method is proposed to accurately calculate the critical strain for DRX by modeling the stress-strain curves obtained from hot compression. The results showed good agreement with experimental data and provided insights into the dynamic softening behaviors during hot deformation.
MATERIALS RESEARCH EXPRESS
(2022)
Article
Engineering, Manufacturing
Bingtao Tang, Mian Li, Ning Guo, Qianchi Li, Lu Han, Zhongguo Zhang
Summary: An extended ductile fracture criterion at elevated temperature was established to accurately predict the initiation of ductile fracture in 7075 aluminum alloy during hot forming process. The influence of dynamic recrystallization (DRX) and stress states on fracture behavior was investigated, and the Z parameter embedded DRX model was introduced into the modified Mohr-Coulomb (MMC) DFC.
INTERNATIONAL JOURNAL OF MATERIAL FORMING
(2023)
Article
Materials Science, Multidisciplinary
Tian Liu, Hengnan Ding, Rui Luo, Leli Chen, Yu Cao, Xiaonong Cheng
Summary: The hot deformation characteristics, microstructure evolution, and dynamic recrystallization mechanism of a newly developed austenitic heat-resistant steel were systematically studied, revealing different recrystallization mechanisms and microstructure features at different strain rates.
METALLURGICAL AND MATERIALS TRANSACTIONS A-PHYSICAL METALLURGY AND MATERIALS SCIENCE
(2021)
Article
Nanoscience & Nanotechnology
Kaveh Edalati, Qing Wang, Nariman A. Enikeev, Laura-Jean Peters, Michael J. Zehetbauer, Erhard Schafler
Summary: The microstructure and mechanical properties of materials reach steady states after severe plastic deformation (SPD). It has been found that the von Mises strain rates do not significantly affect the crystallite/grain size, dislocation density, microhardness, and shear stress at the steady state.
MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING
(2022)
Article
Engineering, Mechanical
Kofi A. Annan, Eric G. Njoroge, Charles W. Siyasiya, Roelf Mostert
Summary: An unexpected explosion of a fifty litre seamless gas cylinder, in service for five years, was caused by fluorine attack on the steel despite good mechanical and material properties as well as manufacturing practices.
ENGINEERING FAILURE ANALYSIS
(2021)
Article
Materials Science, Multidisciplinary
M. N. Mathabathe, A. S. Bolokang, G. Govender, C. W. Siyasiya, R. J. Mostert
Summary: The thermal, surface properties and microstructures of the nitrided gamma-Ti-46Al-2Nb and Ti-46Al-2Nb-0.7Cr-0.3Si intermetallic alloys were investigated. Thin nitride layers formed on both alloys after annealing and nitridation under nitrogen gas, exhibiting surface spallation at different rates during cyclic oxidation. XPS analysis revealed the presence of mixed oxide layer near the Ti-46Al-2Nb-0.7Cr-0.3Si surface.
MATERIALS CHEMISTRY AND PHYSICS
(2021)
Article
Materials Science, Multidisciplinary
N. K. K. Arthur, C. Siyasiya, S. Pityana, M. Tlotleng
Summary: This study investigates the use of direct energy deposition technique in additive manufacturing for alloy development, successfully improving the ductility and part performance of LENS produced titanium alloys by implementing effective heat inputs. The addition of molybdenum as a beta-stabilizing alloying element led to an increase in volume fraction of the beta-phase and a transition from planar to cellular solidification, resulting in hardness values attributed to the beta-stabilizing and grain refining effect of refractory metals like molybdenum.
JOURNAL OF MATERIALS ENGINEERING AND PERFORMANCE
(2021)
Article
Nanoscience & Nanotechnology
K. M. Lekganyane, R. J. Mostert, C. W. Siyasiya, K. M. Banks
Summary: The hot ductility of a low carbon peritectic steel grade was investigated, showing that terminating primary cooling at temperatures 70°C above the ferrite start transformation temperature resulted in poor ductility. The formation of thin ferrite films during rebound heating led to irreversible loss of hot ductility due to finely dispersed second phase particles remaining at the austenite grain boundaries.
MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING
(2021)
Article
Chemistry, Physical
P. Daswa, S. Chikosha, C. W. Siyasiya
Summary: The study investigated the effects of substituting varying amounts of vanadium for titanium in TiPt shape memory alloy on microstructure, crystal structure, and phase transformation. The results demonstrated that the addition of vanadium improved the functional properties and increased the martensitic transformation temperature of TiPt.
Article
Metallurgy & Metallurgical Engineering
Ya-dong Wang, Zheng-hua Tang, Su-fen Xiao, Charles W. Siyasiya, Tao Wei
Summary: The study focused on the strength-to-weight ratio of high-strength low-alloy steel used in pipelines and investigated the effects of thermo-mechanical controlled processing on precipitates and microstructure. The optimized parameters combination was found to be FRT of 820 degrees C and CT of 550 degrees C, resulting in a precipitates volume fraction of 0.59%.
JOURNAL OF IRON AND STEEL RESEARCH INTERNATIONAL
(2022)
Article
Materials Science, Multidisciplinary
Oleary Bill, Charles Siyasiya, Joseph Moema
Summary: The hot deformation behavior of 2304 lean duplex stainless steel was studied using processing maps and physically based constitutive modeling. The results showed that dynamic restoration mechanisms can prevent flow instability at low strain rates, and for typical industrial purposes, hot working at higher strain rates is possible without the risk of instability by promoting dynamic recrystallization in the austenitic phase.
METALLURGICAL AND MATERIALS TRANSACTIONS A-PHYSICAL METALLURGY AND MATERIALS SCIENCE
(2022)
Article
Materials Science, Multidisciplinary
Tulani W. Mukarati, Roelf J. Mostert, Charles W. Siyasiya, Waldo E. Stumpf
Summary: Boltzmann-type sigmoidal equations have been developed to model the tensile strain hardening and flow stress behavior of a metastable AISI 301LN austenitic stainless steel subjected to prior cold deformation. The compressive pre-strain has a strong effect on the material's martensite content, tensile yield strength, and energy absorption capability.
METALLURGICAL AND MATERIALS TRANSACTIONS A-PHYSICAL METALLURGY AND MATERIALS SCIENCE
(2022)
Article
Metallurgy & Metallurgical Engineering
Tulani W. Mukarati, Roelf J. Mostert, Charles W. Siyasiya
Summary: This study investigates the mechanical properties of a lean AISI 301LN austenitic stainless steel under various temperature and strain conditions, revealing the influence of martensite transformation strengthening on the material's behavior. Various measurement techniques are used to accurately describe the kinetics of strain-induced martensite transformation at different temperatures, providing insights into the alloy's performance at different operating conditions.
STEEL RESEARCH INTERNATIONAL
(2022)
Article
Engineering, Mechanical
Tshenolo Phinah Leso, Charles Witness Siyasiya, Roelf Johannes Mostert, Joseph Moema
Summary: Wear and rolling contact fatigue (RCF) are major issues in rail systems, but the presence of lubricants can help reduce their effects. This study focused on the use of water and oil as lubricants, finding that they significantly decreased wear compared to dry conditions. Water was found to cause fluid crack pressurization, leading to RCF.
TRIBOLOGY TRANSACTIONS
(2023)
Review
Materials Science, Multidisciplinary
John J. M. Ellard, Maria N. Mathabathe, Charles W. Siyasiya, Amogelang S. Bolokang
Summary: Relentless efforts over the past decade have led to the commercialization of lightweight high-temperature β-TiAl-based intermetallic alloys. These materials have been used in General Electric's (GE) high bypass turbofan aircraft engines for the Boeing 787 as well as in the PW1100GTF engines for low-pressure turbine (LPT) blades. To enhance the fatigue resistance of the alloys, a clear understanding of their response to fatigue loading is crucial. This review provides a detailed discussion on the low-cycle fatigue (LCF) behavior of β-TiAl-based alloys, including crack initiation, propagation, fracture mechanisms, and the influence of temperature and environment on cyclic deformation mechanisms and fatigue life. Additionally, the review presents comprehensive discussions on modeling and prediction of fatigue properties, as well as effective methods for optimizing the microstructures of β-TiAl-based alloys to improve LCF behavior.
Article
Materials Science, Multidisciplinary
Joseph S. Moema, Charles W. Siyasiya, Veronica K. Morudu, Thokozani Buthelezi
Summary: Due to the increasing demand for energy saving, the need for high-performing automotive heat exchangers has grown significantly. Effective fin-tube heat exchangers, made from AA3003 aluminum alloy, have become popular. The impact of soaking time on the microstructure and mechanical properties of AA3003 cladded with AA4045 alloy was investigated. Precise control of various manufacturing steps is crucial to achieve a high-quality product.
Article
Metallurgy & Metallurgical Engineering
M. G. Willemse, C. W. Siyasiya, D. Marais, A. M. Venter', N. K. K. Arthur
Summary: This research project focuses on the evolution of residual stresses in 3D printed titanium alloy samples. The study found that there were large tensile stresses near the top sections of the samples, which could lead to separation from the baseplate. Additionally, the analysis of microstructures revealed a strong correlation between the macro-segregation of nickel elements and the distribution of the beta phase in the printed parts.
JOURNAL OF THE SOUTHERN AFRICAN INSTITUTE OF MINING AND METALLURGY
(2023)
Article
Metallurgy & Metallurgical Engineering
M. N. Mathabathe, A. S. Bolokang, G. Govender, C. W. Siyasiya, R. J. Mostert
Summary: A series of solidifying γ-TiAl intermetallic alloys were developed and tensile tested at room temperature, showing predominantly lamellar structures with columnar dendritic cores and occasional presence of second phase Ti5Si3. All alloys exhibited brittleness with no detectable ductility during tensile deformation. Fracture surfaces revealed translamellar fracture with few cleavage facets.
JOURNAL OF THE SOUTHERN AFRICAN INSTITUTE OF MINING AND METALLURGY
(2021)
Proceedings Paper
Materials Science, Multidisciplinary
K. A. Annan, P. Daswa, K. Motumbo, C. W. Siyasiya
Summary: Titanium aluminides are considered the optimal materials for specific applications in aerospace and automotive industries due to their high specific strength and high temperature performance, coupled with good oxidation resistance. The production process of these materials greatly influences their mechanical properties.
MATERIALS TODAY-PROCEEDINGS
(2021)