scholarly journals Achieving room-temperature brittle-to-ductile transition in ultrafine layered Fe-Al alloys

2020 ◽  
Vol 6 (39) ◽  
pp. eabb6658
Author(s):  
Lu-Lu Li ◽  
Yanqing Su ◽  
Irene J. Beyerlein ◽  
Wei-Zhong Han
Keyword(s):  
Room Temperature ◽  
Extreme Environments ◽  
High Strength ◽  
Layered Composite ◽  
Al Alloys ◽  
Brittle To Ductile Transition ◽  
Transmission Electron ◽  
Structural Applications ◽  
Wear And Corrosion Resistance ◽  
New Applications

Fe-Al compounds are of interest due to their combination of light weight, high strength, and wear and corrosion resistance, but new forms that are also ductile are needed for their widespread use. The challenge in developing Fe-Al compositions that are both lightweight and ductile lies in the intrinsic tradeoff between Al concentration and brittle-to-ductile transition temperature. Here, we show that a room-temperature, ductile-like response can be attained in a FeAl/FeAl2 layered composite. Transmission electron microscopy, nanomechanical testing, and ab initio calculations find a critical layer thickness on the order of 1 μm, below which the FeAl2 layer homogeneously codeforms with the FeAl layer. The FeAl2 layer undergoes a fundamental change from multimodal, contained slip to unimodal slip that is aligned and fully transmitting across the FeAl/FeAl2 interface. Lightweight Fe-Al alloys with room-temperature, ductile-like responses can inspire new applications in reactor systems and other structural applications for extreme environments.

In situ observation of the martensitic transformation in (Mg,Y)-PSZ

1986 ◽  
Vol 44 ◽  
pp. 500-501
Author(s):  
R-R. Lee
Keyword(s):  
Martensitic Transformation ◽  
High Strength ◽  
Nucleation And Growth ◽  
In Situ Observation ◽  
Considerable Potential ◽  
Transmission Electron ◽  
Structural Applications ◽  
Applied Stresses ◽  
Kinetics Of

Partially-stabilized ZrO2 (PSZ) ceramics have considerable potential for advanced structural applications because of their high strength and toughness. These properties derive from small tetragonal ZrO2 (t-ZrO2) precipitates in a cubic (c) ZrO2 matrix, which transform martensitically to monoclinic (m) symmetry under applied stresses. The kinetics of the martensitic transformation is believed to be nucleation controlled and the nucleation is always stress induced. In situ observation of the martensitic transformation using transmission electron microscopy provides considerable information about the nucleation and growth aspects of the transformation.

Study on the Microstructure and Properties of Low Cost TiFeAl Alloy

2013 ◽  
Vol 477-478 ◽  
pp. 1288-1292
Author(s):  
Bo Long Li ◽  
Tong Liu ◽  
Jie Yuan ◽  
Zuo Ren Nie
Keyword(s):  
Electron Microscopy ◽  
Mechanical Properties ◽  
Low Cost ◽  
High Strength ◽  
Al Alloys ◽  
Vacuum Induction Melting ◽  
Induction Melting ◽  
Β Phase ◽  
Transmission Electron ◽  
Solution Strengthening

The high strength and low cost Ti-Fe based alloy was produced by double vacuum induction melting method followed by hot deformation. The microstructure has been investigated by Optical Microscopy, Scanning Electron Microscopy (SEM), and Transmission Electron Microscopy (TEM). The microstructure of as-forged alloy is composed of α and β phase without the precipitation of TiFe intermetallic compound. The Ti-Fe-Al alloys show good comprehensive mechanical properties, demonstrating ultimate tensile strength of 1100MPa and elongation above10%. The results indicate the Fe is a good candidate for solution strengthening and simultaneously increasing ductility in titanium alloys. Effect of the Fe and Al elements on the microstructure and mechanical properties have been discussed.

TEM Investigations of Titanium Processed by ECAP Followed by Cold Rolling

2006 ◽  
Vol 503-504 ◽  
pp. 805-810 ◽  
Author(s):  
Bernhard Mingler ◽  
V.V. Stolyarov ◽  
Michael Zehetbauer ◽  
Wolfgang Lacom ◽  
Hans Peter Karnthaler
Keyword(s):  
Cold Rolling ◽  
Room Temperature ◽  
High Strength ◽  
Tensile Tests ◽  
Coarse Grained ◽  
Angular Pressing ◽  
Transmission Electron ◽  
Cp Ti ◽  
Annealing Experiments

Conventional coarse grained (CG) commercial pure (CP) Ti Grade 2 was studied after cold rolling (CR) at room temperature, and after equal channel angular pressing (ECAP) at 450° C followed by CR, by transmission electron microscopy (TEM) methods. CR of the CG material leads to a microstructure showing initially twins with (0112) type and later subgrains separated by lowangle grain boundaries. CR carried out after ECAP yields the fragmentation of fine grains (300 – 800 nm) mostly bounded by high-angle boundaries into elongated subgrains (~ 100 nm). It was shown with in-situ annealing experiments in the TEM that this microstructure is thermally stable up to a temperature of 450° C. Tensile tests showed that the combination of ECAP with CR has the potential to produce at the same time high strength (941 MPa) and high ductility (16.7%).

Selection and Design Principles of Wrought Aluminium Alloys for Structural Applications

2012 ◽  
Vol 710 ◽  
pp. 50-65 ◽  
Author(s):  
A.K. Mukhopadhyay
Keyword(s):  
Heat Treatment ◽  
Aluminium Alloys ◽  
High Strength ◽  
Al Alloys ◽  
Alloy Design ◽  
Alloying Elements ◽  
Microstructure And Properties ◽  
Structural Applications ◽  
Treatment Procedures ◽  
Selection Of

This article discusses the fundamental principles associated with the selection of aluminium alloys for specific purposes, alloy design & heat treatment procedures and development of key microstructures responsible for obtaining desired properties in selected wrought Al alloys for aerospace and defence applications. Influence of micro/trace additions of suitable alloying elements on the microstructure and properties of high strength 7xxx series Al alloys is further highlighted.

scholarly journals Achieving strong and stable nanocrystalline Al alloys through compositional design

2021 ◽  
Author(s):  
Qiang Li ◽  
Jian Wang ◽  
Haiyan Wang ◽  
Xinghang Zhang
Keyword(s):  
Thermal Stability ◽  
Grain Refinement ◽  
Room Temperature ◽  
Supersaturated Solid Solution ◽  
High Strength ◽  
Al Alloys ◽  
Mechanical Anisotropy ◽  
Transition Metal Alloys ◽  
Mechanical Strengths ◽  
Tension Compression Asymmetry

Abstract Al alloys often suffer from low mechanical strength and lack high-temperature microstructural and mechanical robustness. A series of binary and ternary nanocrystalline (NC) Al transition metal alloys with supersaturated solid solution and columnar nanograins have been recently developed by using magnetron sputtering, manifesting a new realm of mechanical properties and thermal stability. Distinct solutes cause evident differences in the phase transformations and efficiencies for grain refinement and crystalline-to-amorphous transition. Certain sputtered Al-TM alloys have shown room-temperature mechanical strengths greater than 2 GPa and outstanding thermal stability up to 400 °C. In addition, the NC Al alloys show mechanical anisotropy and tension–compression asymmetry, revealed by micromechanical tests. Through the process encapsulating various compositionally distinct systems, we attempt to illuminate the solute effects on grain refinement and properties and more importantly, tentatively unravel the design criteria for high-strength and yet thermally stable NC Al alloys. Graphic Abstract

Plasticity and Interfacial Dislocation Structures in Ti-Al

1996 ◽  
Vol 460 ◽  
Author(s):  
L. Parrini ◽  
H. Heinrich ◽  
G. Kostorz
Keyword(s):  
Heat Treatment ◽  
Lamellar Structure ◽  
Room Temperature ◽  
Compression Tests ◽  
Interfacial Dislocation ◽  
Brittle To Ductile Transition ◽  
Transmission Electron ◽  
Interfacial Dislocations ◽  
Very High ◽  
Lamellar Interfaces

ABSTRACTThe alloy Ti-48.6Al-l.9Cr-l.9Nb-IB with an equiaxed γ microstructure, obtained by heat treatment at 1200°C for 4 h, and with a lamellar mi ero structure, obtained by heat treatment at 1380°C for 1 h, is characterized by compression tests and transmission electron microscopy. A lower activity of superdislocations and a more frequent pinning of ordinary dislocations are detected in the lamellar Ti-Al specimens in comparison with the non-lamellar ones during deformation at room temperature. The activity of superdislocations and the pinning of ordinary dislocations are responsible for the differences in yield stress and brittleness between lamellar and non-lamellar Ti-Al. A very high density of ordinary interfacial dislocations is found in the lamellar structure. These influence the activity of superdislocations and the pinning of ordinary dislocations. At high temperature a change in the deformation mechanism occurs. Above the brittle-to-ductile transition, the material is remarkably softer and the mechanical properties are insensitive to the presence of the lamellar interfaces.

Comparative Study of the Microstructure and Tensile Properties of Ni-Al Alloys with Fe and Cr Additions

1998 ◽  
Vol 552 ◽  
Author(s):  
E. Pekarskaya ◽  
C. J. Humphreys ◽  
C. N. Jones
Keyword(s):  
High Temperature ◽  
Comparative Study ◽  
Tensile Properties ◽  
Room Temperature ◽  
Al Alloys ◽  
Tensile Behaviour ◽  
Defect Structures ◽  
Two Phase ◽  
Brittle To Ductile Transition ◽  
Phase Intermetallic

ABSTRACTThe tensile behaviour of Ni-32at.% Al-5at.% Fe and Ni-32at.% Al-12 at.% Cr two-phase intermetallic compounds has been studied in the 20–750°C temperature range. TEM studies of the defect structures have been performed. Both alloys exhibit a brittle behaviour at room temperature, while at high temperature the Ni-Al-Cr alloy appears to be much more ductile that the Ni-Al-Fe alloy. Various reasons for the limited ductility and the brittle-to-ductile transition in these alloys are discussed.

scholarly journals High-strength nanocrystalline intermetallics with room temperature deformability enabled by nanometer thick grain boundaries

2021 ◽  
Vol 7 (27) ◽  
pp. eabc8288
Author(s):  
Ruizhe Su ◽  
Dajla Neffati ◽  
Jaehun Cho ◽  
Zhongxia Shang ◽  
Yifan Zhang ◽  
...  
Keyword(s):  
Grain Boundaries ◽  
Room Temperature ◽  
Compressive Strain ◽  
High Strength ◽  
Vital Role ◽  
Transmission Electron ◽  
Micropillar Compression ◽  
Dynamics Simulations ◽  
Nucleation Of Dislocations

Although intermetallics are attractive for their high strength, many of them are often brittle at room temperature, thereby severely limiting their potential as structural materials. Here, we report on a previously unidentified deformable nanocrystalline CoAl intermetallics with Co-rich thick grain boundaries (GBs). In situ micropillar compression studies show that nanocrystalline CoAl with thick GBs exhibits ultrahigh yield strength, exceeding 4.5 gigapascals. Unexpectedly, nanocrystalline CoAl intermetallics also show prominent work hardening to a flow stress of 5.7 gigapascals up to 20% compressive strain. Transmission electron microscopy studies show that deformation induces abundant dislocations inside CoAl grains with thick GBs, which accommodate plastic deformation. Molecular dynamics simulations reveal that the Co-rich thick GBs play a vital role in promoting nucleation of dislocations at the Co/CoAl interfaces, thereby enhancing the plasticity of the intermetallics. This study provides a perspective to promoting the plasticity of intermetallics via the introduction of thick GBs.

SPD-Induced Grain Boundary Segregations and Superior Strength in UFG Al Alloys

2010 ◽  
Vol 667-669 ◽  
pp. 665-669
Author(s):  
Nariman A. Enikeev ◽  
Maxim Yu. Murashkin ◽  
Xavier Sauvage ◽  
Vil U. Kazykhanov ◽  
Ruslan Valiev
Keyword(s):  
Grain Size ◽  
Atom Probe Tomography ◽  
Room Temperature ◽  
High Strength ◽  
Atom Probe ◽  
Mean Value ◽  
Al Alloys ◽  
Ultrafine Grain ◽  
Ultrafine Grain Size ◽  
Grain Boundary Segregations

Two Al alloys (AA1570 and AA6061) in the solutionized state have been processed by HPT at room temperature to achieve a homogeneous UFG structure. After HPT, the grain size was found to have a mean value about 100 nm for both alloys. Measured yield stress values of HPT-produced UFG alloys being plotted in terms of the Hall-Petch relationship were found to exceed the plot predictions for the range of ultrafine grain size. For both alloys, Atom Probe Tomography measurements allowed to reveal segregation of solute elements along grain boundaries. The origin of the extremely high strength of the alloys nanostructured by HPT is discussed with a special attention to the influence of such segregations on the emission and the mobility of dislocations.

Domain Formation in Synthetic Quartz

1971 ◽  
Vol 29 ◽  
pp. 156-157
Author(s):  
Joseph J. Comer
Keyword(s):  
Electron Beam ◽  
Room Temperature ◽  
Domain Formation ◽  
Synthetic Quartz ◽  
Transmission Electron ◽  
Black Spots ◽  
Diffraction Mode ◽  
Domain Boundaries ◽  
Kikuchi Lines ◽  
Straight Lines

Domains visible by transmission electron microscopy, believed to be Dauphiné inversion twins, were found in some specimens of synthetic quartz heated to 680°C and cooled to room temperature. With the electron beam close to parallel to the [0001] direction the domain boundaries appeared as straight lines normal to <100> and <410> or <510> directions. In the selected area diffraction mode, a shift of the Kikuchi lines was observed when the electron beam was made to traverse the specimen across a boundary. This shift indicates a change in orientation which accounts for the visibility of the domain by diffraction contrast when the specimen is tilted. Upon exposure to a 100 KV electron beam with a flux of 5x 1018 electrons/cm2sec the boundaries are rapidly decorated by radiation damage centers appearing as black spots. Similar crystallographio boundaries were sometimes found in unannealed (0001) quartz damaged by electrons.

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