Ultrafine-grained and Heterostructured Materials (UFGH XII): On-Demand Poster Session
Sponsored by: TMS: Shaping and Forming Committee
Program Organizers: Penghui Cao, University of California, Irvine; Xiaoxu Huang, Chongqing University; Enrique Lavernia, University of California, Irvine; Xiaozhou Liao, University of Sydney; Lee Semiatin, MRL Materials Resources LLC; Nobuhiro Tsuji, Kyoto University; Caizhi Zhou, University of South Carolina; Yuntian Zhu, City University of Hong Kong
Monday 8:00 AM
March 14, 2022
Room: Nanostructured Materials
Location: On-Demand Poster Hall
On the Underlying Mechanisms in Binary Ni-based Nanocrystalline Alloys: Keerti Pandey1; Atul Chokshi1; 1Indian Institute of Science
The hardness of binary nanocrystalline Ni-based alloys with segregating solute elements increases upon annealing until a certain temperature and then decreases beyond a critical temperature. In most of these alloys, the grain size increases only slightly while the strength increases and a jump is observed in the grain size post this critical limit. This study critically evaluates the various underlying strengthening mechanisms, including (a) the state of the solute elements at grain boundaries, (b) the formation of second phases, and (c) the role of observed twins in annealed alloys. Various alloy compositions were synthesized using a pulsed electrodeposition method. The experimental observations and analyses are examined in terms of grain boundary stability, strengthening and weakening.
Investigation of Microstructural Inhomogeneity and Mechanical Characteristics of Severely Deformed Copper Sheet: Nikhil Tripathi1; Swapnil Sawalkar1; Kallol Mondal1; Shashank Shekhar1; 1IIT Kanpur
Constrained groove pressing is a severe plastic deformation process, which is known to improve mechanical properties of materials. Studies have shown that CGP processed materials contain inherent microstructural inhomogeneity due to which properties like hardness shows non-uniformity at micro-level. This strain inhomogeneity arises due to sharp edges of die where both bending and shear deformation occurs while rest of sample region experiences only shear deformation. Since bending strain is inversely proportional to radius of curvature, hence, changing the radius of curvature of corners is expected to minimize the impact of bending strain. Recent studies have shown that this strain inhomogeneity also broadly depends on pressing orientation of sheets and CGP-CR (cross route) is an efficient way of injecting strain symmetrically along both longitudinal and transverse directions of specimen. In this work, we investigate how microstructural inhomogeneity and mechanical properties can be modified by changing die design along with processing route
Microstructure Evolution in Additively Manufactured and High-pressure Torsion Processed High-entropy Alloys during Heating as Characterized by Neutron Diffraction: Xiaojing Liu1; Jae-Kyung Han2; Yusuke Onuki3; Yulia O Kuzminova4; Stanislav A Evlashin4; Megumi Kawasaki2; Klaus-Dieter Liss1; 1Guangdong Technion – Israel Institute of Technology; 2Oregon State University; 3Ibaraki University; 4Skolkovo Institute of Science and Technology
The microstructure evolution during heating of a 3d-printed and high-pressure torsion processed high entropy alloy CoCrFeNi is investigated using in-situ neutron diffraction. For comparison, the same experiment is performed on the as-printed high entropy alloy. Because of strain anisotropy in as-printed material, the modified Wiiliamson-Hall method is calculated from the conventional Willamson-Hall plot by applying a dislocation model. The evolution of dislocation density during heating can be detected. Different behavior upon heating of as-printed, as-cast and HPT processed high entropy alloys can be revealed by peak width analysis to distinguish recovery, recrystallization and grain growth. Finally, the texture also plays a role during above mentioned processes.
Ultrafine δ-ferrite and Transformation-induced Plasticity in Laser Melting Deposition Processed 304L Austenitic Stainless Steel: Jung Gi Kim1; Jonghyun Jeong1; Yukyeong Lee1; Jeong Min Park2; Dong Jun Lee3; Hyoung Seop Kim2; Taehyun Nam1; Hyokyung Sung1; Jae Bok Seol1; 1Gyeongsang National University; 2Pohang Univerisity of Science and Technology; 3Korea Institute of Materials Science
Rapid melting and solidification cycles during laser-based additive manufacturing create non-equilibrium microstructure in the stainless steels including Cr/Mo segregations that induce an ultrafine δ-ferrite in the matrix. Contradictory to the coarse δ-ferrite in the conventional stainless steels, ultrafine δ-ferrite in the additively manufactured stainless steels has a coherency with γ-austenite matrix and interacts with dislocations. Because the interaction between coherent metastable δ-ferrite and dislocations may contributes to the mechanical property of additively manufactured alloys, in the present work, the role of ultrafine δ-ferrite on the plastic deformation behavior of laser melting deposition processed 304L stainless steel was investigated. The α’-martensitic transformation behavior depends on the initial grain size of 304L stainless steels that results into the different mechanical property in the different processing condition. Moreover, the ultrafine δ-ferrite maintains a coherency with γ-austenite matrix even in high deformation region and prolongs the plasticity of additively manufactured 304L stainless steel.
Effect of Processing Temperature on the Microstructure and Mechanical Properties Changes of High-pressure Torsion Processed Al7075 Alloy: Juhee Oh1; Sangeun Park1; Hyo Ju Bae1; Sujung Son2; Hyoung Seop Kim2; Jae Bok Seol1; Hyokyung Sung1; Jung Gi Kim1; 1Gyeongsang National University; 2Pohang University of Science and Technology
Severe plastic deformation at an elevated temperature results into the complex microstructure including dynamic recovery and solute migration. Especially, low-melting temperature alloys (e.g. aluminum and magnesium) are sensitive to additional heat energy that results into the abnormal grain growth or dynamic precipitations during severe plastic deformation. In this study, the mechanical properties and microstructural evolution of high-pressure torsion-processed aluminum 7075 alloy at a high temperature are investigated. In the early deformation stage, both grain refinement and nano-precipitates are formed that increase the strength of ultrafine-grained aluminum alloy. In the later deformation stage, however, strength decreases due to the grain growth and coarse precipitates act as crack initiation sites during plastic deformation. This result shows the additional heat during high-pressure torsion accelerates precipitation behavior in the matrix, and the generated precipitations contribute to the mechanical property of ultrafine-grained bulk metallic alloys.
Deformation Mechanism of Magnesium Alloy with Heterogeneous Ultrafine Structures Composed of Soft and Hard Domains: Jongbin Go1; Myeong-Heom Park1; Si Gao1; Nobuhiro Tsuji1; 1Kyoto University
Metallic materials with heterogeneous nanostructures often show superior mechanical properties managing both high strength and good tensile ductility, but details of their deformation mechanism are still unclear. In the present study, we aim to fabricate hetero-nanostructured magnesium (Mg) alloy and to investigate its deformation mechanism. Mg and Mg alloys have attracted great attention as the lightest structural metallic material. Due to their HCP crystal structure, orientation distributions in microstructures can be also counted as a source of mechanical heterogeneity. Conventional AZ31 Mg alloy with HCP single-phase structure is processed through heavy deformation (including severe plastic deformation) and subsequent heat treatments for fabricating heterogeneous ultrafine structures composed of soft and hard domains. Details of their microstructures and mechanical properties will be shown in the presentation.
In-situ X-ray Diffraction Study on Tensile Deformation of TRIP-assisted Metastable Austenitic Fe-Ni-C Steel: Sungsoon Kang1; Si Gao1; Wenqi Mao2; Yu Bai3; Myeongheom Park1; Hiroki Adachi4; Masugu Sato5; Nobuhiro Tsuji1; 1Kyoto University; 2J-PARC center; 3Dalian University of Technology; 4University of Hyogo; 5Japan Synchrotron Radiation Research Institute (JARSI)
Tensile test with in-situ high energy synchrotron X-ray diffraction at the beam line BL46XU of SPring-8 was carried out on a TRIP-assisted metastable austenitic Fe-Ni-C specimen having an excellent combination of a high ultimate tensile strength and a good tensile elongation . The change in the volume fraction of deformation induced martensite during tensile deformation of the sample was precisely measured using the diffraction profiles. Besides that, analysis of phase stresses in austenite and martensite was performed measured by the diffraction peak shift due to the elastic deformation of the phases in response to the external load. The results showed a moderate transformation rate of the strain induced martensite, and a dramatic phase stress partitioning between the deformation induced martensite and the austenite during plastic deformation.