Ultrafine-grained and Heterostructured Materials (UFGH XI): Poster Session 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 5:30 PM
February 25, 2020
Room: Sails Pavilion
Location: San Diego Convention Ctr
N-34: Measurement of Strain Effects on Electrical Conductivity and Wear Properties in Materials Processed by High Pressure Torsion: Evander Ramos1; Takahiro Masuda2; Sina Shahrezaei1; Zenji Horita2; Suveen Mathaudhu3; 1University of California Riverside; 2Kyushu University; 3University of California, Riverside
It is well-documented that high-pressure torsion (HPT) can create heterogeneous microstructures depending on the amount of shear strain imparted. This strain-based inhomogeneity has not been adequately accounted for in many works reporting electrical conductivity of materials processed by HPT. Conversely, when it comes to wear properties in HPT materials, research has mostly focused on pin-on-disc tests that elucidate behavior only at discrete levels of strain. In this work, HPT-processed discs were cut in a spiral pattern to obtain a uniform cross section with monotonically increasing strain, thereby enabling a more precise study of electrical properties throughout the sample. Additionally, linear reciprocating wear tests were conducted in regions of varying strain and compared to literature to assess any differences from continuous wear tests. Thus, this work provides a framework to better understand the variation of electrical and wear properties as a function of strain in HPT-processed materials.
N-35: Mechanical and Electrical Properties of an Ultrafine Grained Al-0.7Fe-0.1Si-0.2Er Alloy Processed by ECAP: Xingchi He1; Yue Zhang1; Xiaoguang Yuan1; Fuyu Dong1; Ruichun Wang1; Weiqi Wang1; 1School of Material Science and Engineering, Shenyang University of Technology
Outstanding mechanical and conducticity properties are vital to Al alloys used in electronic area. However, high strength and high electrical conductivity are mutually exclusive in metallic materials. This study focuses on the effect of equal-channel angular pressing (ECAP) on thermostability, microstructure, mechanical properties and electrical conductivity of an Al-0.7Fe-0.1Si-0.2Er alloy as well as their evolutions after annealing. The ingot was firstly homogenized at 570℃ for 1h, and then extruded 1, 2, 4, 8 passes, respcectively. ECAP processing leads to formation of a very homogeneous ultrafine grained microstructure making the tensile yield strength, ultimate tensile strength, and microhardness of the UFG samples higher than thoes of the CG samples. Though, ECAP processing induces a significant reduction of the electrical conductivity, but it was restored by annealing thanks to the addition of RE atoms, recovery and recrystallization. This study shows that severe plastic deformation has the potential applications in Al alloys conductors.
N-36: Microstructure and Tensile Behavior of Nanostructured Gradient TWIP Steel: Jie Ding1; Zhongxia Shang1; Jin Li1; H. Wang1; Xinghang Zhang1; 1Purdue University
Gradient nanostructured metallic materials have shown unique mechanical properties, such as high strength and good work hardening ability. The mechanisms of gradient structure induced work hardening remain less well understood. Here a TWIP steel with large equiaxed grains was processed by surface mechanical grinding treatment, and the subsequent gradient structures formed near surface consist of surface nanolaminate layer, a mixed layer of deformation twins and shear bands, and a deformation twin layer. Tensile studies show that the gradient structures increase the yield strength of the TWIP steel prominently. Strain hardening appears to reach maxima near the interface regions between the layers. ASTAR crystal orientation map indicates distinct transition of high angle grain boundaries and twin boundaries near interfaces as well as the accumulation of geometrically necessary dislocations. These in-depth studies provide insight into the design of high strength, work hardenable gradient nanostructured alloys.
N-37: Nucleation, Growth and Coarsening of Precipitates in Immiscible Alloys during Low-temperature Severe Plastic Deformation: Gibbs-Thomson Behavior: Nirab Pant1; Yinon Ashkenazy2; Nisha Verma1; Robert Averback1; 1University of Illinois, Urbana-Champaign; 2Hebrew University of Jerusalem
Severe plastic deformation (SPD) of strongly-immiscible alloys such as dilute Cu-Nb and Cu-Mo leads to novel steady-state microstructures featuring nanoprecipitates with a self-selected size distribution and a super-saturation of solute atoms in the matrix. While there have been various models proposed for how large precipitates might shrink under shear deformation, little work has considered how small precipitates nucleate and grow during SPD, particularly at low temperatures where thermally activated diffusion is negligible. Here, we demonstrate using molecular dynamics simulations that low-temperature SPD can be described within an effective temperature model, and that a key prediction of this model is Gibbs-Thomson (G-T) behavior. While G-T behavior does lead to the growth and coarsening of precipitates, the simulations also show that agglomeration of precipitates is the dominant growth mechanism.
N-38: Optimization of Mechanical Properties and Corrosion Resistance of Ultra-fine Grained Titanium By Low-temperature Annealing: Agata Sotniczuk1; Krzysztof Topolski1; Halina Garbacz1; 1Warsaw University of Technology
Annealing deformed metals usually leads to reduced strength. In the case of nano and ultra-fine grained (UFG) materials, the opposite effect was observed after low-temperature annealing. This unusual phenomenon may be related to the 1) reduction of mobile dislocation density and changes in the grain boundaries state, 2) segregation of impurities, 3) crystallographic texture changes. This factors may also affect the quality of the protective passive layers formed spontaneously on UFG titanium surface and, thereby its corrosion resistance. Hence, in this work the possibility of increase both hardness and corrosion resistance of UFG Ti was investigated. UFG Ti was fabricated by multiple-pass cold rolling performed by different deformation paths. The changes of mechanical and corrosion properties were explained based on the microstructure evolution induced by low-temperature annealing. This work was supported by NCN Poland [2018/29/B/ST8/02883]
N-39: Pressure Effects during High Pressure Torsion of Dilute Magnesium-Yttrium: Christian Roach1; Kiran Solanki2; Suveen Mathaudhu1; 1University of California, Riverside; 2Arizona State University
High pressure torsion (HPT) can refine most metals to the nanocrystalline regime but magnesium’s high recovery rate limits the minimum achievable grain size. HPT is typically performed at the highest pressure available, since this increases the metastable dislocation density which in turn is expected to result in finer grains. However, materials with high recovery rates show increased static recovery at higher dislocation density. A reduction in processing pressure limits the number of dislocations that can be introduced and may minimize this post-processing static recovery. Yttrium reduces basal texture and improves plasticity through activation of cross-slip, thus magnesium-yttrium (3 wt% ) was processed at pressures of 1, 3, & 5 GPa through five rotations in order to unravel the effects of processing pressure on microstructural refinement. Electron microscopy points to increased static recovery with increased pressure while micro-tensile testing shows reduced elongation to failure.
Cancelled
N-40: Size-dependent Strengthening and Conductivity of Highly-textured Cu/BN Multilayers: Naiqi Chen1; Houyu Ma1; Yue Liu1; Tongxiang Fan1; 1Shanghai Jiao Tong University
Heterogeneous interfaces play a very important role in improving mechanical and physical properties of composite materials. In this study, highly textured Cu/BN multilayers with individual layer thickness (h) varying from 2 to 75 nm were fabricated by magnetron sputtering. Indentation harnesses of multilayer increase with decreasing h, approaching to a peak hardness of 57GPa, and softening thereafter at smaller h. Different deformation mechanisms of multilayers at different h are identified, ranging from typical Hall-Petch model to co-deformation. This phenomenon may be attributed to large modulus mismatch and strong heterogeneous interfacial bonding. Moreover, insulated c-BN and fully-coherent Cu/BN heterogeneous interface are beneficial to reduce electron scattering. Size-dependent electrical conductivity of multilayers is identified that is ascribed to both interface and grain boundary scattering.
Cancelled
N-41: Stress Transfer in Heterogeneous Nanostructured Single-phase High Manganese Steel Investigated by In Situ Synchrotron Radiation: Xing Fang1; Kaiyuan Yu1; 1China University of Petroleum, Beijing
A heterogeneous structured single-phase high manganese steel composed of nanolaminated and submicron equiaxed grains was fabricated by wire drawing and partial recrystallization. The nanolaminated grains are strongly <111> textured in contrast to the randomly oriented equiaxed grains. In situ synchrotron XRD and TEM results reveal that equiaxed grains yield first during deformation at an applied strain of ~0.5% (~650 MPa applied stress), transferring part of the flow stress to nanolaminated grains. Subsequently, the equiaxed grains share increasing fraction of flow stress owing to higher strain hardening rate. As a result, the flow stress of the equiaxed grains exceeds that of the nanolaminated grains at an applied strain of ~6%, leading to a second stress transfer. The results may shed light on understanding the deformation behavior of heterogeneous nanostructured single-phase alloys.
N-42: Studying on the Role of Heterogeneous Interface in Graphene/Metal Composites for Enhancing the Irradiation Tolerance: Kunming Yang1; Yue Liu1; Houyu Ma1; Di Chen1; Tongxiang Fan1; 1Shanghai Jiao Tong University
High-dose, high-energy particle irradiation often induces severe microstructural damages in metals, thus leading to significant degradation of mechanical and physical properties. Heterogeneous interface in composites has proven to be ideal sinks for irradiation-induced defects. Herein, we use the graphene (Gr)/Cu composites as a model material to study the role of heterogeneous interface in Gr/metal composites for enhancing the irradiation tolerance. The results showed that the irradiation-induced defects prefer to migrate towards Gr/Cu interface instead of the high-angle Cu grain boundary. Besides, although the electrical resistivity (Ω) of composites increased after He+ implantation, the Ω increased magnitude significantly decreased when increasing the Gr content, manifesting remarkable enhanced irradiation tolerance. Apart from the strong defect sink ability of the Gr/Cu interface, the anti-irradiation mechanism also lies in the impenetrable character of Gr. The present findings may open a new path to develop Gr/metal composites for future advanced nuclear materials.
N-43: Synchrotron-based High-resolution Reciprocal Space Mapping to Understand Elasto-plastic Transition in Harmonic Structured Materials: Elis Sjogren1; Wolfgang Pantleon2; Ulrich Lienert3; Zoltan Hegedüs3; Kei Ameyama4; Dmytro Orlov1; 1Lund University; 2Technical University of Denmark; 3Deutsches Elektronen Synchrotron; 4Ritsumeikan University
Harmonic structured (HS) materials have been proposed to enhance structural performance without altering chemical composition. They have a bimodal grain-size microstructure, which consists of a continuous fine-grained network encompassing coarse-grain islands. The elastic-plastic behavior of such materials under mechanical loading needs to be understood. In this work, differences in elasto-plastic behavior between coarse- and fine-grains were investigated in HS pure Ni in comparison to coarse-grained pure Ni using high-energy synchrotron X-rays at Petra III. In situ tensile testing was performed until the early stages of plastic yielding. High-resolution reciprocal space mapping was used as a principal technique for monitoring the concurrent microstructure evolution. It is found that in the HS material, plastic deformation onsets in large grains at stress levels below the proof stress while fine grains deform elastically beyond this stress level. This indicates strain partitioning and confirms earlier reports on the unique elasto-plastic behaviour in HS materials.
N-44: Synthesis and Mechanical Characterization of Metallic Films with Highly Controlled Heterogeneous Microstructures: Rohit Berlia1; Jagannathan Rajagopalan1; 1Arizona State University
Materials with heterogeneous microstructures have been shown to exhibit a superior combination of strength and toughness compared to homogeneous nanostructured or coarse-grained materials. However, only limited progress has been made in controlling these heterogeneous microstructures. Here we report a novel technique to synthesize metallic films with highly tailored multimodal microstructures using magnetron sputtering. This technique enabled us to precisely control the grain size dispersion, volume fraction and spatial arrangement of the grains. We synthesized bimodal films of Nickel, Copper, Aluminum and Iron where the mean size of smaller grains is around 40-250 nm while larger grains have mean sizes exceeding 5 µm. The microstructure was characterized by a combination of XRD, EBSD and TEM to reveal grain size dispersion, texture and orientation distribution. The deformation behavior was investigated using MEMS tensile testing device. The results demonstrate the potential of this technique to precisely tailor the mechanical behavior of metallic films.