scholarly journals Austempering Experiments of Production Grade Silicon Solution Strengthened Ductile Iron

2018 ◽  
Vol 925 ◽  
pp. 239-245
Author(s):  
Kaisu Soivio
Keyword(s):  
Ductile Iron ◽  
High Strength ◽  
Heat Treatments ◽  
Strengthening Effect ◽  
Iron Carbides ◽  
The Matrix ◽  
Solution Strengthening ◽  
Grade Silicon ◽  
The Stability

Austempered ductile iron provides a feasible way to produce high strength components. However, in heat treatments resulting in highest strengths some of the ductility is lost due to formation of bainitic carbides. The role of silicon in inhibiting the formation of iron carbides in as-cast ductile irons as well as its solution strengthening effect is well known and acknowledged in industry. The effect of silicon on austemperability, resulting microstructures, and mechanical properties of austempered ductile irons with silicon contents with 3.4-3.8 w-% was researched. Quenching and austempering heat treatments were carried out for production grade silicon solution strengthened ductile irons EN GJS 500-14. Results indicate, that it is possible to manufacture a fully ausferritic structure into a silicon solution strengthened matrix and indeed good ductility can be achieved in combination with ultimate tensile strength of 1600 MPa. Segregation of silicon reduces the solubility of carbon into the matrix especially close to the graphite nodules which reduce the stability of carbon stabilized austenite and leads into compromised machinability.

scholarly journals Biomimetic Composites with Enhanced Toughening Using Silk Inspired Triblock Proteins and Aligned Nanocellulose Reinforcements

2019 ◽  
Author(s):  
Pezhman Mohammadi ◽  
A. Sesilja Aranko ◽  
Christopher P. Landowski ◽  
Olli Ikkala ◽  
Kristaps Jaudzems ◽  
...  
Keyword(s):  
Spider Silk ◽  
Cellulose Nanofibrils ◽  
High Strength ◽  
Beta Sheets ◽  
Conformational Switching ◽  
Multiple Length Scales ◽  
The Matrix ◽  
Strength And Stiffness ◽  
Flow Alignment

Silk and cellulose are biopolymers that show a high potential as future sustainable materials.They also have complementary properties, suitable for combination in composite materials where cellulose would form the reinforcing component and silk the tough matrix. Therein, a major challenge concerns balancing structure and properties in the assembly process. We used recombinant proteins with triblock architecture combining structurally modified spider silk with terminal cellulose affinity modules. Flow-alignment of cellulose nanofibrils and triblock protein allowed a continuous fiber production.The protein assembly involved phase separation into concentrated coacervates, with subsequent conformational switching from disordered structures to beta sheets. This gave the matrix a tough adhesiveness, forming a new composite material with high strength and stiffness combined with increased toughness. We show that versatile design possibilities in protein engineering enable new fully biological materials, and emphasize the key role of controlled assembly at multiple length scales for realization.<br>

Influence of Multi-Step Austempering Temperature on Tensile Performance of Unalloyed Ductile Iron

2019 ◽  
Vol 803 ◽  
pp. 3-7
Author(s):  
Wei Ci Zhuang ◽  
Ying Ming Jiang ◽  
Wen Tao Zhou ◽  
Zhong Yang Liang ◽  
Derek O. Northwood ◽  
...  
Keyword(s):  
Ductile Iron ◽  
Isothermal Holding ◽  
Bainitic Ferrite ◽  
High Strength ◽  
Rapid Quenching ◽  
Air Cooling ◽  
Strengthening Effect ◽  
Multiphase Structure ◽  
Tensile Performance ◽  
Austempering Temperature

Austempered ductile iron (ADI) has been widely used in various industries due to its excellent combination of high strength, ductility and good wear resistance. The tensile behavior of an unalloyed commercial ADI with a multiphase structure designed by a novel multi-step austempering treatment is investigated. The developed austempering process consists of austenitizing at 890°C for 20min, then initial rapid quenching to 180°C, and isothermal holding at 190, 220, 250°Cfor 120min, and finally air cooling to room temperature. The optimum mechanical properties with an ultimate tensile strength of 1350MPa, a yield strength of 1090MPa, as well as an elongation of 3.5% is achieved at 220°C. This is attributed to a synergistic strengthening effect of multiphase structure including a prior martensite with fine needle bainitic ferrite and film retained austenite.

The Effects of Substitutional Additions on Creep Behavior of Tetragonal and Hexagonal Nb-Silicides

2002 ◽  
Vol 753 ◽  
Author(s):  
B. P. Bewlay ◽  
C. L. Briant ◽  
E. T. Sylven ◽  
M. R. Jackson
Keyword(s):  
Creep Behavior ◽  
High Strength ◽  
Aircraft Engine ◽  
Great Promise ◽  
Silicide Phase ◽  
Monolithic Phases ◽  
Phase Ordering ◽  
The Stability

ABSTRACTNb-silicide based in-situ composites combine a ductile Nb-based solid solution with high-strength silicides, and they show great promise for aircraft engine applications. The Nb-silicide controls the high-temperature creep behavior of the composite. Previous work has shown that the silicide composition has an important effect on the creep rate, with particular attention on the role of Ti and Hf additions. The aim of the present study is to understand the effects of the substitutional elements on the stability of the silicide phase, ordering in the crystal lattice, including the hP16-tI32 transition, and the creep behavior of the monolithic phases. To pursue this goal monolithic alloys with a range of compositions were prepared and the creep rates were measured at temperatures of 1100–1350°C. The stress sensitivities of the creep rates of the monolithic phases were also determined.

scholarly journals A New High Strength High Ductile Nodular Iron

2018 ◽  
Vol 925 ◽  
pp. 224-230 ◽  
Author(s):  
Werner Menk
Keyword(s):  
Solid Solution ◽  
Ductile Iron ◽  
High Strength ◽  
Ductile Material ◽  
European Standard ◽  
Serial Production ◽  
Solid Solution Strengthening ◽  
New Family ◽  
Solution Strengthening ◽  
Proof Strength

Years ago, especially in Sweden, a new family of ductile iron materials was propagated: Solid solution strengthened ferritic ductile iron. Since the 2011 edition, three grades are integrated into the European Standard EN 1563: EN-GJS-450-18, EN-GJS-500-14 and EN-GJS-600-10. The introduction of these materials into the European standard generated a large interest of many engineers, which came to a real hype meanwhile. The reason is clear: While GJS-450-18 is not very different from the standard GJS-400-15, especially the grade EN-GJS-500-14 promises to have big advantages compared to the standard grade EN-GJS-500-7. Same tensile strength, from 320 MPA to 400 MPa raised 0.2%- proof strength and from 7% to 14 % doubled elongation after fracture are very interesting properties of course and the pure ferritic structure promises a better machinability furthermore. With the higher strength grade EN-GJS-600-10 very early sceptic comments raised, because the Silicon content to reach the required strength is such high, that the risk of an embrittlement of the ferrite even at room temperature and on a tensile test bar is high. But up to now, the grade EN-GJS-500-14 has the reputation to be a high strength and very high ductile material. So, a customer of us also substituted a part from steel to EN-GJS-500-14. All calculations showed a very good performance of the parts, but as soon as in serial production field damages occurred in a manner that the parts completely broke without advance warning. The investigation of the damages showed, that the parts are not only statically and cyclically loaded, but also by strikes. Deeper investigations about strike loads confirmed, that EN-GJS-500-14 is not really ductile under these conditions. The reflection to the philosophy we had with our SiboDur-700 concept, namely to combine a moderate solid solution strengthening with a moderate strengthening by pearlite with Copper, brought us to a new high strength high ductile material we call SiboDur-500. Same strength as EN-GJS-500-14, 10 % lower in 0.2%- proof stress, slightly lower in elongation after fracture, but double to more than four times energy consumption at strike loads depending om temperature!

Microstructure and Mechanical Properties of a Single Crystal NiAl Alloy with Zr or HF Rich G-Phase Precipitates.

1990 ◽  
Vol 213 ◽  
Author(s):  
I. E. Locci ◽  
R. D. Noebe ◽  
R. R. Bowman ◽  
R. V. Miner ◽  
M. V. Nathal ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Single Crystal ◽  
Single Crystals ◽  
Heat Treatments ◽  
Strengthening Effect ◽  
Slow Cooling ◽  
Large Plate ◽  
Nial Alloy ◽  
Large Particles ◽  
The Matrix

ABSTRACTThe possibility of producing NiAl reinforced with the G-phase (Ni16X6Si7), where X is Zr or Hf, has been investigated. The microstructures of these NiAl alloys have been characterized in the as-cast and annealed conditions. The G-phases are present as fine cuboidal precipitates (10 to 40 nm) and have lattice parameters almost four times that of NiAl. They are coherent with the matrix and fairly resistant to coarsening during annealing heat treatments. Segregation and non-uniform precipitate distribution observed in as-cast materials were eliminated by homogenization at temperatures near 1600 K. Slow cooling from these temperatures resulted in large plate shaped precipitates, denuded zones, and a loss of coherency in some of the large particles. Faster cooling produced a homogeneous fine distribution of cuboidal G-phase particles (≤10 nm) in the matrix. Preliminary mechanical properties for the Zr-doped alloy are presented and compared to binary single crystal NiAl. The presence of these precipitates appears to have an important strengthening effect at temperatures≥1000 K compared to binary NiAl single crystals.

scholarly journals Biomimetic Composites with Enhanced Toughening Using Silk Inspired Triblock Proteins and Aligned Nanocellulose Reinforcements

2019 ◽  
Author(s):  
Pezhman Mohammadi ◽  
A. Sesilja Aranko ◽  
Christopher P. Landowski ◽  
Olli Ikkala ◽  
Wolfgang Wagermaier ◽  
...  
Keyword(s):  
Spider Silk ◽  
Cellulose Nanofibrils ◽  
High Strength ◽  
Beta Sheets ◽  
Conformational Switching ◽  
Multiple Length Scales ◽  
The Matrix ◽  
Strength And Stiffness ◽  
Flow Alignment

Silk and cellulose are biopolymers that show a high potential as future sustainable materials.They also have complementary properties, suitable for combination in composite materials where cellulose would form the reinforcing component and silk the tough matrix. Therein, a major challenge concerns balancing structure and properties in the assembly process. We used recombinant proteins with triblock architecture combining structurally modified spider silk with terminal cellulose affinity modules. Flow-alignment of cellulose nanofibrils and triblock protein allowed a continuous fiber production.The protein assembly involved phase separation into concentrated coacervates, with subsequent conformational switching from disordered structures to beta sheets. This gave the matrix a tough adhesiveness, forming a new composite material with high strength and stiffness combined with increased toughness. We show that versatile design possibilities in protein engineering enable new fully biological materials, and emphasize the key role of controlled assembly at multiple length scales for realization.

scholarly journals Effects of Mo, Nb, Ta, Ti, and Zr on Mechanical Properties of Equiatomic Hf-Mo-Nb-Ta-Ti-Zr Alloys

Entropy ◽  
2018 ◽  
Vol 21 (1) ◽  
pp. 15 ◽  
Author(s):  
Ko-Kai Tseng ◽  
Chien-Chang Juan ◽  
Shuen Tso ◽  
Hsuan-Chu Chen ◽  
Che-Wei Tsai ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Solid Solution Phase ◽  
Refractory Element ◽  
Strengthening Effect ◽  
Cast State ◽  
High Entropy ◽  
Pros And Cons ◽  
Solution Strengthening ◽  
Zr Alloys

Nowadays refractory high-entropy alloys (RHEAs) are regarded as great candidates for the replacement of superalloys at high temperature. To design a RHEA, one must understand the pros and cons of every refractory element. However, the elemental effect on mechanical properties remains unclear. In this study, the subtraction method was applied on equiatomic HfMoNbTaTiZr alloys to discover the role of each element, and, thus, HfMoNbTaTiZr, HfNbTaTiZr, HfMoTaTiZr, HfMoNbTiZr, HfMoNbTaZr, and HfMoNbTaTi were fabricated and analyzed. The microstructure and mechanical properties of each alloy at the as-cast state were examined. The solid solution phase formation rule and the solution strengthening effect are also discussed. Finally, the mechanism of how Mo, Nb, Ta, Ti, and Zr affect the HfMoNbTaTiZr alloys was established after comparing the properties of these alloys.

Interaction of Dislocations with Impurities and its Influence on the Mechanical Properties of Silicon Crystals

1982 ◽  
Vol 14 ◽  
Author(s):  
Koji Sumino
Keyword(s):  
Mechanical Properties ◽  
Mechanical Strength ◽  
Dynamic Behavior ◽  
Light Element ◽  
High Strength ◽  
Heat Treatments ◽  
Macroscopic Scale ◽  
Silicon Crystals ◽  
The Matrix ◽  
Influence Of Impurities

ABSTRACTA review is presented of the work on the influence of impurities on the dynamic behavior of dislocations in silicon crystals and also on the resulting effects in the mechanical strength performed by the author's group. Special emphasis is laid on the effects of light element impurities such as oxygen, nitrogen and carbon. Although all of these impurities do not affect the velocities of dislocations moving under relatively high stresses, oxygen and nitrogen atoms are found to lock slowly moving dislocations and dislocations at rest very effectively. Such locking of dislocations results in the decreases in the activities of generation and multiplication centers for dislocations, leading to the strengthening of the crystals. The high strength of silicon crystals brought about by the impurities is lost when the crystals are subjected to the heat treatments which allow the precipitation of the impurities on a macroscopic scale. This softening is shown to be caused by dislocations punched out from precipitates and by the exhaustion of the impurities dissolved in the matrix crystal.

scholarly journals Development of Bio-Inspired Hierarchical Fibres to Tailor the Fibre/Matrix Interphase in (Bio)Composites

Polymers ◽  
2021 ◽  
Vol 13 (5) ◽  
pp. 804
Author(s):  
Estelle Doineau ◽  
Bernard Cathala ◽  
Jean-Charles Benezet ◽  
Julien Bras ◽  
Nicolas Le Le Moigne
Keyword(s):  
High Performance ◽  
Load Transfer ◽  
Hierarchical Structures ◽  
High Strength ◽  
The Matrix ◽  
High Performance Composite ◽  
Hierarchical Architectures ◽  
Mechanical Performances ◽  
Fibre Matrix

Several naturally occurring biological systems, such as bones, nacre or wood, display hierarchical architectures with a central role of the nanostructuration that allows reaching amazing properties such as high strength and toughness. Developing such architectures in man-made materials is highly challenging, and recent research relies on this concept of hierarchical structures to design high-performance composite materials. This review deals more specifically with the development of hierarchical fibres by the deposition of nano-objects at their surface to tailor the fibre/matrix interphase in (bio)composites. Fully synthetic hierarchical fibre reinforced composites are described, and the potential of hierarchical fibres is discussed for the development of sustainable biocomposite materials with enhanced structural performance. Based on various surface, microstructural and mechanical characterizations, this review highlights that nano-objects coated on natural fibres (carbon nanotubes, ZnO nanowires, nanocelluloses) can improve the load transfer and interfacial adhesion between the matrix and the fibres, and the resulting mechanical performances of biocomposites. Indeed, the surface topography of the fibres is modified with higher roughness and specific surface area, implying increased mechanical interlocking with the matrix. As a result, the interfacial shear strength (IFSS) between fibres and polymer matrices is enhanced, and failure mechanisms can be modified with a crack propagation occurring through a zig-zag path along interphases.

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