Ultrafine-grained and Heterostructured Materials (UFGH XI): Processing & Microstructure II
Sponsored by: TMS Materials Processing and Manufacturing Division, TMS: Mechanical Behavior of Materials Committee
Program Organizers: Caizhi Zhou, University of South Carolina; Megumi Kawasaki, Oregon State University; Enrique Lavernia, University of California, Irvine; Terry Lowe, Colorado School of Mines; Suveen Mathaudhu, Colorado School of Mines; Ruslan Valiev, UFA State Aviation Technical University; Yuntian Zhu, City University of Hong Kong
Tuesday 2:00 PM
February 25, 2020
Room: Marina Ballroom D
Location: Marriott Marquis Hotel
Session Chair: Zenji Horita, Kyushu Insitute of Technology; Hyoung Kim, Pohang University of Science and Technology; Kenong Xia, University of Melbourne; Megumi Kawasaki, Oregon State University
2:00 PM Invited
Effect of High-pressure Torsion on a Few Mechanical and Electrical Behaviors of Commercially Pure Cu: Praveen Kumar1; Ajay Rijal1; Shobhit Singh1; Jae-Kyung Han2; Megumi Kawasaki2; 1Indian Institute of Science; 2Oregon State University
Cu being a key element in various electronics devices, that undergo cyclic mechanical loading, requires optimum combination of mechanical and electrical properties. Commercially pure Cu is processed through high-pressure torsion (HPT) at 6 GPa up to 50 turns. The effect of HPT on microhardness, resistivity, and fatigue was evaluated and correlated with microstructure. It is observed that HPT process produced ultra-fine grains as low as ~300 nm. Low-angle boundaries and twins boundaries formed at onset of straining that transformed into high grain boundaries on further straining. Microhardness enhanced by ~240%, whereas increment in resistivity was about ~27% as compared to annealed Cu. Furthermore, HPT processed Cu samples showed lesser fraction of persistent slip-bands in the initial stages of fatigue testing and appears to enhance fatigue life. An overview of the observed properties, based on correlation with microstructure conducted using electron back-scattered diffraction and transmission electron microscopy, will be presented
2:20 PM Invited
Mechanical Properties and Residual Stress of Copper Processed using Ultrasonic-nanocrystalline Surface Modification: Hyoung Seop Kim1; 1; 1Pohang University of Science and Technology
Recently, a new surface SPD called the ultrasonic nanocrystalline surface modification (UNSM) technique has exhibited improved global mechanical properties as well surface properties of the processed material. Effects of surface grain refinement and residual stress on the local and global properties of pure Cu processed using ultrasonic nanocrystalline surface modification (UNSM) was investigated. To distinguish each contribution to the local hardness and global tensile properties of the UNSM treated Cu, a stress-relief specimen of the same microstructure as the UNSM treated one was produced by low-temperature annealing after the UNSM treatment. The distinct contributions of residual stress and surface grain refinement to the tensile property of UNSM treated Cu were determined and discussed.
2:40 PM
Mechanical Properties of Nanocrystalline High-entropy Alloys Produced By High-pressure Torsion: Benjamin Schuh1; 1Erich Schmid Institute of Materials Science
Equiatomic high-entropy alloys , namely CrMnFeCoNi, CrCoNi as well as TiZrNbHfTa are processed by high-pressure torsion in order to achieve a nanocrystalline (NC) microstructure and subsequently annealed (t = 1 h) for temperatures between 300°C to 1000°C. The aim of the investigation is twofold: to analyse the microstructure stability and to study the impact of possible phase decompositions on the mechanical properties. Therefore microstructural analysis was performed and microstructure-property relationships were established via subsequent tensile tests. The thermodynamic instability of the face-centered-cubic CrMnFeCoNi and the body-centered-cubic TiZrNbHfTa alloys will be highlighted and the profound changes of their mechanical properties, caused by the formation of second phases, will be discussed. Lastly, a strategy to circumvent the problem of low ductility via bimodal grain size engineering in the NC CrCoNi will be presented, where tensile ductility could be improved to 10% while still retaining ultra-high strengths of 1.5 GPa.
3:00 PM
Microstructures and Mechanical Properties of Supersaturated Al-Mg Alloys Produced by Powder Consolidation using High-pressure Torsion: Yongpeng Tang1; Takahiro Masuda2; Shoichi Hirosawa2; Zenji Horita3; Yuji Higo4; Yoshinori Tange4; Yasuo Ohishi4; 1Kyushu University; 2Yokohama National University; 3Kyushu Institute of Technology; 4Japan Synchrotron Radiation Research Institute
Mixtures of high-purity elemental powders of Al with an Mg content of 20 wt% were consolidated to fabricate bulk supersaturated Al-Mg alloys by high-pressure torsion (HPT). Their microstructures and mechanical properties were examined by X-ray diffraction (XRD) analysis, transmission electron microscopy (TEM), Vickers microhardness test and tensile test. In this study, in-situ experiment was also conducted using high-energy X rays at SPring-8 in JASRI (Japan Synchrotron Radiation Research Institute) to examine the aging behavior. Hardness was improved significantly to 295HV with straining by HPT processing for 60 revolutions. Furthermore, age-hardenability of the supersaturaed Al-Mg alloy was investigated while aging at a low temperature of 343 K which is in the region below the spinodal line.
3:20 PM Break
3:40 PM Invited
Microstructure and Microtexture of Gradient Metals Processed by Asymmetric Rolling: Alexander Zhilyaev1; Hailiang Yu2; Alexander Pesin3; 1Magnitogorsk State Technical University; Institute for Metals Superplasticity Problems of Russian Academy of Science; 2Central South University; 3Magnitogorsk State Technical University
There is a considerable interest in developing metallic materials with ultrafine grains (UFG), directed towards structural applications where exceptional mechanical properties are required. It is feasible to fulfill it successfully when processing metals and alloys, under severe plastic deformation (SPD) techniques. One of the new methods is based on generating a high-accumulated deformation through asymmetric rolling (AR) was developed. The report presents recent results on microstructure and microtexture of FCC pure metals (aluminum and copper) processed by this method. Comparison with known data on Al and Cu processed by traditional techniques of severe plastic deformation (high- pressure torsion and equal channel angular pressing) is present.
4:00 PM Cancelled
In-situ Observation of Ultrafine-grained Heterostructured Pure Titanium by Severe Plastic Deformation under High Pressure: Zenji Horita1; Daisuke Maruno2; Yukimasa Ikeda2; Keisuke Matsuo2; Makoto Arita2; Yuji Higo3; Yoshinori Tange3; Yasuo Ohishi3; 1Kyushu Institute Technology; 2Kyushu University; 3JASRI
Titanium (Ti) exhibits allotropic phase transformation from α phase with hcp crystal structure to ω phase with simple hexagonal crystal structure upon application of pressures more than ~4 GPa. However, the ω phase may remain at ambient pressure if plastic strain is introduced under application of the pressure. Furthermore, the ω phase is more likely to form by the assistance of plastic strain. In this study, in-situ experiment was conducted using high-energy X rays at SPring-8 in JASRI (Japan Synchrotron Radiation Research Institute) to examine the transformation behavior. For this experiment, we used a process of high-pressure sliding where severe plastic deformation is introduced under high pressure. Our challenging is to produce a heterostructure in pure Ti where the ω phase is finely dispersed in the α phase matrix, and thus to increase the strength of pure Ti without addition of alloying elements.
4:20 PM
Microscructure Evolution in CuZr Alloy and cp Ti Processed by a Novel Technique of Rotational Free Bending: Tomáš Krajnák1; Miloš Janeček1; Petr Harcuba1; Peter Minárik1; Cinthia Corręa1; Jakub Čížek1; Arsenyi Raab2; Georgy Raab2; 1Charles University; 2Ufa State Aviation Technical University
A novel technique referred to as rotational free bending was employed to produce gradient fine grained microsctructures in CuZr alloy and commercial pure (cp) titanium. A newly designed die allowing a continuos and repetitive movement of a workpiece through a set of rollers in a channel bent by 90 degrees was employed to produce a series of billets after different number of passes. Microstructure evolution along the cross section of individual billets in both materials was observed by light microscopy and microhardess measurement. The formation of the heterogeneous fine grained structure in the material during one pass was consistent with theoretical modelling of strain distribution by FEM. EBSD analysis from the selected arreas revealed the continuous microstructure fragmentation with increasing number of passes. The variations in dislocation density with strain imposed to the material by free bending was characterized in detail by positron annihilation spectroscopy and complemented by X-ray diffraction.
4:40 PM
Heterostructured Titanium with Superior Tensile Properties through Hybridisation of Microstructures by Selective Laser Melting: Kenong Xia1; 1University of Melbourne
Hybrid materials are abundant in nature, but it is challenging to realise in metals. A new strategy is pioneered for future alloys by hybridising the microstructures of existing alloys using selective laser melting (SLM). To demonstrate the potential of this novel concept, a new class of titanium, referred to as HYbrid Ti Alloy (HYTA), was created by hybridising two existing Ti alloys, one alpha/beta and one metastable beta. An excellent combination of high strength, work hardening rate, uniform and total elongations was achieved, far superior to conventional Ti and rivalling the advanced high strength steels. Further, individual properties of HYTA are amenable to manipulation via simple heat treatment, resulting in great versatility. This innovative approach can be applied to a vast variety of metals beyond Ti, leading to unlimited choices, and contributes significantly to the coming era of microstructure-by-design.