13th International Conference on the Technology of Plasticity (ICTP 2021): Microstructure & Damage Development IV
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

Thursday 9:15 AM
July 29, 2021
Room: Virtual: Room C
Location: Virtual

Session Chair: Pierre-Olivier Bouchard, CEMEF-Mines Paris Tech PSL


The Influence of Temperature and Strain Rate on the Superplastic Deformation Behavior and Microstructure Evolution of TNW700 Alloy: Lixia Ma1; Min Wan1; Weidong Li1; Jie Shao2; Xuepiao Bai2; 1Beihang University; 2AVIC Manufacturing Technology Institute
    TNW700 titanium, as a near-α high temperature titanium alloy, is designed to work at 700°C for a short term service. Superplastic deformation behaviour of TNW700 alloy was investigated in a temperature range of 900-975°C and a strain rate range of 0.0005-0.01s -1 to identify the optimum deformation temperature and strain rate. The microstructure evolution after high temperature tensile was investigated using scanning electron microscope. The research found that TNW700 alloy has an excellent superplasticity. The elongation exceeds 200% at various deformation conditions except 975°C with higher strain rate of 0.005 and 0.01s-1, and the maximum elongation of 613% was obtained at temperature of 925°C and strain rate of 0.001s-1. The flow stress is sensitive to temperature and strain rate, and it increases with decreasing temperature and increasing strain rate. In addition, the flow stress exhibits strongly work hardening with increasing of true strain, and the instantaneous work hardening exponent n and the critical hardening strain is accelerated as the strain rate decreases. The strain rate sensitivity exponent (m) is higher than 0.4 when the temperature is lower than 975°C, which corresponds to dynamic recrystallization and grain boundary sliding. The m is 0.229 at temperature of 975°C, corresponding to dynamic grains growth mechanism. The deformed microstructure of TNW700 alloy consists of β grains and equiaxed α grains. Increasing the temperature is beneficial to the transformation of α phase into the β phase, which resulted in an increase in the volume fraction of the β phase. The β grains growth rapidly at higher temperatures and lower strain rates due to higher diffusion coefficient.

The Study of Energy Absorption of Dual-material Tailored Plane Strain Sheet: Ying Pengfei1; Ge Yulong1; Xia Yong1; 1School of Vehicle and Mobility,Tsinghua University
     The combination of high strength and good ductility are very desirable for functional structures. Laser ridgeline quenching, as a relatively new technology to reinforce steels, gives a flexible to balance the rigidity and toughness of the tubular structures like A-pillar and sill. However, the deformation incompatibility, which is caused by partial quenching, could lead to a structural fracture under impact conditions.In this study, we suppose to investigate the plastic deformation and fracture behavior of partial quenched hot forming steel HR1500. First, quasi-static and dynamic tensile tests are conducted on the original and laser-quenched steels. Second, tensile tests are conducted on the partial quenched steels with three different boundary directions. Finally, the scanning electron microscopy-based electron backscatter diffraction is used to characterize the micro-structure evaluation and the feature of fracture of materials.

Hot Cutting of Press-hardened Parts in Different Heat Treatment Regimes: Rainer Schmidt1; Anja Rautenstrauch1; Verena Kräusel1; 1Technische Universität Chemnitz
    Parts made of press-hardened steels are cut in general by laser cutting. Shear cutting at room temperature of materials with a tensile strength above 1,500 MPa is not an alternative due to insufficient tool life quantity. The presented investigation relates to the hot cutting of press hardenable materials such as 22MnB5 and 34MnB5 and includes the determination of the cutting parameters (measuring rate of 100,000 Hz), the temperature and the formation of the microstructure and the dimensional accuracy of the cut parts during different heat treatments. The results of this investigation show that, when comparing two process routes, the maximum cutting force was reduced to approx. 70 % when cutting in the austenitic range, the acceleration during the cutting impact was close to zero and the deviations from the target geometry were very small. With regard to the measurement results, hot cutting can be an alternative to laser cutting.

Microstructural Influences on Grain Boundary Sliding in High Purity Aluminum: Marissa Linne1; Thomas Bieler2; Samantha Daly3; 1Lawrence Livermore National Laboratory; 2Michigan State University; 3University of California at Santa Barbara
    The presented work investigates grain boundary sliding (GBS), a grain boundary-enabled deformation mechanism, and its relationship with local plasticity and microstructural neighborhood. GBS is characterized experimentally at grain boundaries in 99.99% aluminum with a through-thickness, coarse-grained microstructure deformed in tension at 190 °C. High-resolution strain fields and microstructural information were measured to examine the influence of microstructural neighborhoods on interactions between GBS and slip transmission and strain localization. The findings include (1) direct transmission and GBS were anti-compatible and facilitated by opposing boundary types (low misorientation and high energy grain boundaries respectively); (2) increased GBS activity was correlated with decreased indirect transmission behavior and (3) GBS accommodation at triple junctions was enabled by intragranular plasticity. This work provides insight into the nature of GBS activity and can be used to identify strain transfer criteria that can lead to improved GBS-sensitive crystal plasticity models.

Statistical Analysis of Microscopic Strain Localization and Its Strain Level Dependence: Hyunseok Oh1; Krista Biggs1; Onur Guvenc1; Shaolou Wei1; Jiyun Kang1; Cemal Cem Tasan1; 1Massachusetts Institute of Technology
    Deformation-induced microstructural strain localization is a key process determining various mechanical properties of metallic materials, including formability. However, due to the complexity of the strain localization patterns, most studies investigate this phenomena qualitatively. Recently it was shown that the statistical distribution of local strain in various steels follow a universal law, i.e., a lognormal distribution. To understand this behavior further, we performed a statistic study of strain localization in various single phase and multi-phase alloys. Based on these observations, we propose a parameter to describe the statistical distribution of localized strain. Furthermore, as the loss of viable facets at high deformation levels handicaps this approach, we propose a "stitching" method, that enables the investigation of strain localization at later stages of deformation, even up to fracture.