Materials Processing Fundamentals: Thermomechanical Processing
Sponsored by: TMS Extraction and Processing Division, TMS: Process Technology and Modeling Committee
Program Organizers: Jonghyun Lee, Iowa State University; Guillaume Lambotte, Boston Metal; Samuel Wagstaff, Oculatus Consulting; Antoine Allanore, Massachusetts Institute of Technology; Fiseha Tesfaye, Metso Metals Oy, Ċbo Akademi University
Wednesday 8:30 AM
February 26, 2020
Room: 13
Location: San Diego Convention Ctr
Session Chair: Yunbo Wang, Caterpillar Inc.; Samuel Wagstaff, Novelis Inc.
8:30 AM
The Effect of Thermomechanical Processing on the Microstructural Evolution of Nickel-based Alloy 625: Christopher Martin1; Eric Palmiere2; Andrew Barrow3; Jason Swan3; Grace Burke1; 1The University of Manchester; 2The University of Sheffield; 3Rolls-Royce
Nickel-base Alloy 625 is used in energy-generation applications due to its strength and corrosion resistance at elevated temperatures. However, thermomechanical processing of the alloy can be challenging, leading to the development of variable microstructures within large monolithic forgings. This can result in unpredictable mechanical properties. As a result, there is a need to understand the behaviour of nickel-base alloys during forging operations. In this study, the microstructural evolution in Alloy 625 has been evaluated during laboratory-scale deformations performed at temperatures, strains and strain rates of interest to industry. Typically, these alloys readily undergo dynamic recrystallization during compression, which, if not fully completed, results in unfavourable partially recrystallized microstructures. In order to avoid these regimes, experiments have been performed to assess recrystallization kinetics for Alloy 625. Microstructural characterization using SEM, TEM and EBSD has been performed on compression specimens to develop understanding of the effect of thermomechanical processing on microstructural evolution.
8:50 AM
Observation of Recrystallization Behavior of Nb-microalloyed Wide Flange Beams during Hot Rolling: Bon Seung Koo1; Jae Chang Song1; 1Hyundai Steel
Nb-microalloying has a significant effect on microstructure evolution during hot rolling. Metallurgical benefits of niobium is associated with the formation of Nb(C,N) in ferrite and austenite, retardation of austenite recrystallization, and further austenite to ferrite phase transformation. Precipitation and microstructure control are therefore important features to achieve better strength and toughness simultaneously. Hot rolling conditions, e.g., temperature, roll force and cooling rate, on strength and toughness is of great interest due to the rolling parameters contribute to strengthening mechanism of micro-alloyed steels. Grain refinement is the most practical way to enhance the niobium-bearing steels by strain-induced precipitation hardening below the non-recrystallization temperature. This rolling research involves residual stress variation associated with parallel-flange section geometry. Therefore, repetitive hardening-softening mechanism could be an important feature to predict the final mechanical properties. Computational and experimental analysis has been used to determine flow stress according to the temperature change in hot rolling. The recrystallization behavior is experimentally observed through the multiple rolling.
9:10 AM
Hot Deformation Behavior and Processing Maps of 9Cr1Mo Rotor Steel: Sumit Kumar1; Sumeer Nath1; 1IIT Roorkee
Isothermal hot compression behavior of low-carbon high-alloy 9Cr1Mo rotor steel was studied under the deformation temperature range from 850 °C-1100 °C over the strain rates of 0.001 s-1-10 s-1 up to 0.69 true strain. Artificial neural network (ANN) model was used to analyze the adiabatic temperature rise and flow stress. The activation energy, material constants and Zener-Hollomon parameter with the help of universal constitutive equation were analyzed. Critical condition parameters developed by Jonas & Poliak for the initiation of dynamic recrystallization (DRX) were applied. Material constants ‘n’ & ‘k’ were determined at each deformation condition for Avrami equation model to determine volume fraction of DRX up to 0.69 true strain. The dynamic material model (DMM) and modified dynamic material model (MDMM) (processing maps) were developed at 0.3 and 0.6 true strain, also the microstructural studies were carried out to identify desired forging parameters of present steel.
9:30 AM
Teaching Metal-forming Processes Using a Laboratory Micro-extrusion Press: Adi Benartzy1; Snir Ben Ze’ev1; Nahum Frage1; 1Ben Guriyon University
Metal forming is widely used in the automotive, aviation and energy industries. These days, universities are not equipped with laboratories where students can conduct metal-forming experiments at elevated temperatures. Therefore, teaching metal-forming processes is based on computer simulations, with no "hands-on" experience. Hydraulic indirect extrusion laboratory was constructed to support educational activities. The extrusion press allows student to extrude aluminum, and magnesium alloys up to 650°C using variety of dies. A computerized system controls collects on-line temperature and movement of the ram data. Students investigates the effects of die profile and temperatures on the extrusion forces, and metal properties. Experiments allow students to experience the influence of extrusion parameters on the microstructure and hardness of the extruded alloys. Students find good agreement between the measured and calculated extrusion forces using empirical equations. The influence of different extrusion parameters on the microstructure and mechanical properties of the extruded metals are demonstrated.
9:50 AM Break
10:10 AM Cancelled
Investigation and Numerical Modeling of Aluminum Alloys Depending on Different Thermomechanical Processes: Bedirhan Guraydin1; Metehan Dİincer1; Sadık Kaan İpek2; Halenur Konbul3; Derya Dispnar4; Ahmet Karaaslan1; 1YTU; 2Teknik Alüminyum NPD (New Product Development) and Process Development Department ; 3TEI; 4ITU
In this study, the change in the electrical conductivity of aluminum alloys -AA3005, AA3104, AA3105- produced by twin roll continuous casting method depending on different deformation ratio (50% -95%) and the increased heat treatment temperatures (220-480℃) were researched. The electrical conductivity change for each annealing process of cold rolled parts were measured. According to the obtained results, sample data were statistically modelled with polynomial regression analysis with Minitab, with the regression equations electrical resistance and conductivity properties could be predictable with before the thermo-mechanical process for given aluminum alloys. The aim of this study is determining electrical conductivity before production by creating a numerical model.
10:30 AM Cancelled
The Impact of Inclusions on the Formability of Multiphase Hot-rolled Advanced High Strength Steels: Samaneh Alibeigi1; Emmanuel Lucas1; 1Global R&D, ArcelorMittal Maizières-Les-Metz, France
Steel industries are challenged to produce high strength steels with enhanced properties and excellent formability for production of complex automotive components. One of the important factors affecting steel formability is the presence of nonmetallic inclusions whose detrimental effects can depend on their size, density and chemistry. Therefore, a deep understanding of the factors influencing the inclusions formation is critical for process optimization in steel plants to improve steel formability. An experimental study with controlled steel making processing as well as thermodynamic calculations have been performed to demonstrate the influence of “inclusions forming” elements variation (Ti, N, S, Al, Ca) on inclusions formation in a multiphase hot-rolled steel. Advanced electron microscopy and software program permitted in-depth analysis of inclusions characteristics. Modified mechanical and various forming tests coupled with microstructural analysis and fractography were carried out to investigate the correlation between inclusions characterization and steel formability. Finally, the chemistry-process-inclusions-formability links are discussed.
10:50 AM Cancelled
Effects of Heat Treatment Method on Microstructure and Mechanical Properties of Internal Crack Healing in SA 508-3 Steel: Yao Qiu1; Ruishan Xin2; Jianbin Luo1; Qingxian Ma1; 1Tsinghua University; 2HBIS Group Technology Research Institute
The mechanical property is an important index to evaluate the recovery degree of the internal crack zone. This work presents interfacial characteristics and Charpy impact properties of crack healing zones in SA 508-3 steel, healing by hot compression and different holding treatment. As the holding time increased, the hardness of the matrix and crack healing zone decreased, and the hardness difference between these regions was narrowed. The percentage recovery of impact property increased when the holding time increased from 0h to 10h. After holding for more than 10h, the impact property decreased due to the mixed crystal structure. With the same total holding time, the increase of heating times slowed down the recovery rate of crack healing. It was observed that grain coarsening in the matrix. The results show that for a specimen healing at 950℃, only holding for 10h once is enough for crack healing without sacrifice impact property.
11:10 AM Cancelled
Coarsening of Ferrite Lamella in Heavily Cold Drawn Pearlitic Steel Wire: Feng Fang1; Lichu Zhou1; Jianku Shang2; Jianqing Jiang1; 1Southeast University; 2University of Illinois at Urbana-Champaign
Microstructure and mechanical properties of heavily cold drawn pearlitic steel wires were investigated. Tensile strength of pearlitic steel wires increased from 1420 MPa to 5120 MPa as the drawing strain (ε) increased to 5.7. As the strain ε is less than 4.5, the rate of work hardening is relative high. While the drawing strain ε is over 4.5, the rate of work hardening decreased rapidly. Atom probe tomography (APT) shows that carbon atoms were evenly distributed in ferrite in pearlitic wires (ε=4.5). It is due to the dissolution of cementite during the heavily cold drawing process. And the coarsening of nano-lamellae ferrite was observed in cold drawn wire (ε=4.7). Increasing the carbon content of steel wire and low temperature annealing with heavily cold drawn wires were useful methods to delay the coarsening of nano-lamellae ferrite. A higher tensile strength of pearlitic steel wires could be achieved.