13th International Conference on the Technology of Plasticity (ICTP 2021): Microstructure Development by Forming I
Program Organizers: Glenn Daehn, Ohio State University; Libby Culley, The Ohio State University; Anupam Vivek, Ohio State University; Jian Cao, Northwestern University; Brad Kinsey, University of New Hampshire; Erman Tekkaya, TU Dortmund; Yoshinori Yoshida, Gifu University
Tuesday 10:20 AM
July 27, 2021
Room: Virtual: Room C
Location: Virtual
Session Chair: Darcy Hughes, Sandia National Labs (ret.)
Microstructure Evolution during Isothermal Forging of 7A85 Aluminum Aviation Component: Hu Jianliang1; Youping Yi2; Miao Jin1; Hong Bo1; 1Yanshan University; 2Central South University
A 7085 aluminum aviation component with high ribs and thin webs was successfully formed by the isothermal forging process, and its microstructure was investigated by optical microscope (OM), transmission electron microscope (TEM) and cellular automaton simulation. The cellular automaton model of 7A85 aluminum alloy, including dislocation density model, nucleation rate equation as well as grain growth model was established, and the parameters of the cellular automaton models were determined by the hot compression experiment on the thermal-mechanical simulator Gleeble-1500. The cellular automaton simulation results agree well with the optical micrographs of the aviation forging, showing good homogeneity in both the size and the distribution of grain structure. The TEM images show that a homogeneous distributed dislocations and precipitates of the forging formed by the isothermal forging process can be attained, which can inhibit the migration of the grain boundaries, resulting in the small and uniform grains of the aviation forging.
Forming of Parts with Locally Defined Mechanical and Ferromagnetic Properties by Flow-forming: Eugen Wiens1; Werner Homberg1; Bahman Arian1; 1Paderborn University
To generate a highly efficient use of material resources for formed parts a locally adoption of required strength and integrated functions is advised. By using austenitic steel, the volume fraction of deformation-induced alpha martensite, which has an influence on the strength and the magnetic permeability of the material, is highly dependent on the degree of deformation and the workpiece temperature in the deformation zone. By selective adjustment of the process parameters wall thickness reduction Δs and deformation temperature Td it was possible to produce local restricted areas with an alpha martensite volume from almost negligible to 80 % at the same deformation stage, using a spinning or flow forming process. This way axially graded and locally varying mechanical and sensory properties, e.g. for a magnetic displacement sensor, can be produced. The aim of this ongoing work is a closed loop control of properties by using micromagnetic sensors during spinning processes.
Cancelled
Microstructure and Thermomechanical Properties of AA7075 Sheet Metal Processed by ECAP: Maximilian Gruber1; Christian Illgen2; Philipp Frint2; Martin Wagner2; Wolfram Volk1; 1Chair of Metal Forming and Casting; 2Institute of Materials Science and Engineering
Equal-channel angular pressing (ECAP) is an established method for the improvement of mechanical properties by grain refinement. While there is a profound knowledge about ECAP of bulk materials, there is only little information on the effect of ECAP on sheet metals. In this contribution the effect of ECAP at different temperatures (20, 75, 150 and 225 °C) and processing routes (A, C and D) on the microstructure and mechanical properties of AA7075 aluminum sheets is investigated. The microstructure is examined using Electron Backscatter Diffraction (EBSD). The results show that microstructural changes and precipitation kinetics could be affected using different configurations. Furthermore, the mechanical properties of the ECAP material is characterized by tensile tests at different temperatures. It was found that the materials strength is controlled by ECAP and the corresponding processing conditions. Due to the specific microstructural features the thermomechanical properties could be considerably improved for future practical applications.
Data Preparation in the Digital Material Representation Based 3D Cellular Automata Model of Static Recrystallization: Lukasz Madej1; Mateusz Sitko1; Mateusz Mojzeszko1; Lukasz Rychlowski1; Dawid Zych1; Konrad Perzynski1; Grzegorz Cios1; 1AGH University of Science and Technology
Development of the complex three dimensional cellular automata model of recrystallization is the overall goal of the research. To properly capture local heterogeneities, in grain morphology, crystallographic orientation as well as distribution of stored energy after deformation, the digital material representation concept and finite element modelling are used. Two different approaches for generation of digital microstructure model subjected to numerical simulation of deformation conditions and subsequent heat treatment were developed and are presented. In the first case, results from electron backscattered diffraction based serial sectioning method are used to provide input data on 3D microstructure state. In the second case, numerical Monte Carlo grain growth model to generate representative volume element was developed. Examples of obtained microstructural data and their influence on cellular automata static recrystallization simulation results are also presented.
Study of the Influence of the Mixed-grain Structure on the Microscopic Deformation Behavior of 316LN Steel: YangQi Li1; Haiming Zhang1; Mingxiang Liu1; Zhenshan Cui1; 1Shanghai Jiao Tong University
Mixed-grains are common microstructures for heavy forgings. Taking 316LN austenitic stainless steel as an investigated material, two kinds of grain structures were tested for observation of microscopic deformation heterogeneity: uniform fine grains and mixed structures with millimeter-grade coarse grains (MCGs). Tensile tests and EBSD as well as OM observations were performed. Results showed that the deformation of the MCGs exhibited single slip if they were with soft orientation, and cross slip if they were with hard orientation. Obvious slip bands were observed in the MCGs. The fine grains were seen easily rotated in the deformation, forming distinguished bumpy grain boundaries, while the MCGs displayed smooth grain morphologies. The interior MCGs undertook severer deformation than the fine grains, which showed the strain partitioning ability of MCGs were limited. This deformation behavior is capable to lead the crack initiation in the interface of MCGs and fine grains.
Thermomechanical Analysis and Experimental Validation of ECAP for Aluminum Sheet Metal: Maximilian Gruber1; Yiheng Yang1; Christian Illgen2; Philipp Frint2; Martin Wagner2; Wolfram Volk1; 1Chair of Metal Forming and Casting, TU Munich; 2Institute of Materials Science and Engineering, TU Chemnitz
Equal-channel angular pressing is an established method for the improvement of mechanical properties by grain refinement through shear strains. While there is a profound knowledge about ECAP of bulk materials, there is only little information on the effect of ECAP on sheet metals. Therefore a tool was developed which is able to perform ECAP-tests for metals with a thickness of 1.8 mm. In this contribution a thermomechanical simulation model is used to examine the novel process. The simulation is performed to investigate the dissipated forming heat and the heat due to friction. To validate the numerical results, experiments are performed. By drilling holes in the material the forming temperature can be measured with thermocouples and the friction can be calibrated inversely. In this way, fundamental correlations between the heat development in the ECAP process for Aluminum sheet metal and the shear strain implied in the material can be obtained.