scholarly journals Microstructural and Mechanical Characterization of a Nanostructured Bainitic Cast Steel

Metals ◽  
2020 ◽  
Vol 10 (5) ◽  
pp. 612 ◽  
Author(s):  
Andrés Felipe Santacruz-Londoño ◽  
Oscar Rios-Diez ◽  
José A. Jiménez ◽  
Carlos Garcia-Mateo ◽  
Ricardo Aristizábal-Sierra
Keyword(s):  
Cast Steel ◽  
Isothermal Holding ◽  
High Strength ◽  
Cast Steels ◽  
Final Microstructure ◽  
Potential Applications ◽  
Steel Castings ◽  
Kinetics Of ◽  
Holding Temperature

Nanoscale bainite is a remarkable microstructure that exhibits a very promising combination of high strength with good ductility and toughness. The development of these types of microstructures has been focused on wrought materials, and very little information is available for steel castings. In this work, a specially designed cast steel with 0.76 wt % C was fabricated, and the heat treatment cycles to develop bainitic nanostructures were determined by studying the kinetics of the bainitic transformation using high-resolution dilatometry. The effects of isothermal holding temperature and time on the final microstructure and mechanical properties were thoroughly characterized in order to evaluate a future industrial implementation of the process in an effort to contribute to enhance and widen the potential applications for cast steels.

scholarly journals Facile Synthesis and Characterization of Palm CNF-ZnO Nanocomposites with Antibacterial and Reinforcing Properties

2021 ◽  
Vol 22 (11) ◽  
pp. 5781
Author(s):  
Janarthanan Supramaniam ◽  
Darren Yi Sern Low ◽  
See Kiat Wong ◽  
Loh Teng Hern Tan ◽  
Bey Fen Leo ◽  
...  
Keyword(s):  
Plant Biomass ◽  
Cellulose Nanofibers ◽  
High Strength ◽  
Salmonella Typhi ◽  
Particle Sizes ◽  
Mechanical Reinforcement ◽  
Uniform Size ◽  
Preparation Methods ◽  
Potential Applications

Cellulose nanofibers (CNF) isolated from plant biomass have attracted considerable interests in polymer engineering. The limitations associated with CNF-based nanocomposites are often linked to the time-consuming preparation methods and lack of desired surface functionalities. Herein, we demonstrate the feasibility of preparing a multifunctional CNF-zinc oxide (CNF-ZnO) nanocomposite with dual antibacterial and reinforcing properties via a facile and efficient ultrasound route. We characterized and examined the antibacterial and mechanical reinforcement performances of our ultrasonically induced nanocomposite. Based on our electron microscopy analyses, the ZnO deposited onto the nanofibrous network had a flake-like morphology with particle sizes ranging between 21 to 34 nm. pH levels between 8–10 led to the formation of ultrafine ZnO particles with a uniform size distribution. The resultant CNF-ZnO composite showed improved thermal stability compared to pure CNF. The composite showed potent inhibitory activities against Gram-positive (methicillin-resistant Staphylococcus aureus (MRSA)) and Gram-negative Salmonella typhi (S. typhi) bacteria. A CNF-ZnO-reinforced natural rubber (NR/CNF-ZnO) composite film, which was produced via latex mixing and casting methods, exhibited up to 42% improvement in tensile strength compared with the neat NR. The findings of this study suggest that ultrasonically-synthesized palm CNF-ZnO nanocomposites could find potential applications in the biomedical field and in the development of high strength rubber composites.

Microstructural Control of 7075 Al Wrought Alloys through Thixoextrusion Route

2006 ◽  
Vol 510-511 ◽  
pp. 362-365 ◽  
Author(s):  
Young Ok Yoon ◽  
Hyung Ho Jo ◽  
Jin Kyu Lee ◽  
Dong In Jang ◽  
Shae K. Kim
Keyword(s):  
Grain Size ◽  
Liquid Fraction ◽  
Isothermal Holding ◽  
High Strength ◽  
Industrial Applications ◽  
High Productivity ◽  
Die Life ◽  
Average Grain Size ◽  
Low Energy Consumption ◽  
Holding Temperature

Thixoextrusion, one of the thixoforming processes, has advantages of high productivity, reduction of the extrusion pressure, extension of the die life, and cost saving owing to its low energy consumption compared with the conventional extrusion processes. Especially, thixoextrusion process is expected to be very effective for hard-to-form materials with high strength. The present study focuses on 7075 Al wrought alloy to investigate the potential industrial applications of the thixoextrusion process. The microstructural evolution of 7075 Al wrought alloy for thixoextrusion was investigated with respect to isothermal holding temperature and time in the partially remelted semisolid state. The results showed that the liquid fraction increased with increasing isothermal holding temperature and time while the average grain size was inversely proportional to isothermal holding temperature and time up to 5min. However, there was no big change of liquid fraction and average grain size with respect to isothermal holding temperature and time. The important fact that the liquid fraction and average grain size were almost uniform after 5 min holding time is considered very useful for thixoextrusion in terms of process control.

Processing and Characterization of Porous Ti2AlC Using Space Holder Technique

2016 ◽  
Vol 704 ◽  
pp. 197-203 ◽  
Author(s):  
Jesus Gonzalez-Julian ◽  
Martin Bram
Keyword(s):  
Low Cost ◽  
High Strength ◽  
Max Phase ◽  
Space Holder ◽  
Porous Ti ◽  
Low Thermal Expansion ◽  
Final Microstructure ◽  
Ammonium Hydrogen ◽  
Oxidation And Corrosion

Ti2AlC is one of the most promising MAX phase materials due to its combination of properties at high temperatures (> 800 °C) such as high strength, good oxidation and corrosion resistances, low thermal expansion, readily machinable, high thermal conductivity and nonsusceptibility to thermal shock. Porous structures based on Ti2AlC are excellent candidates for diverse applications such as heat exchangers and filters, although more systematic studies are required to implement this material. In this work, porous Ti2AlC material was obtained using a low cost and eco-friendly process, the space holder technique. Commercial Ti2AlC powder was mixed with different contents (30, 50 and 70 vol.%) of ammonium hydrogen bicarbonate (NH4HCO3) as space holder. Afterwards, the obtained powder was uniaxially pressed, followed by elimination of space holder by a heat treatment at low temperature. Finally, porous Ti2AlC structures were consolidated at 1350 °C under argon atmosphere. Processing, final microstructure and pore characterization of the consolidated materials are described in detail.

scholarly journals Development of Nanobainitic Microstructures in Carbo-Austempered Cast Steels: Heat Treatment, Microstructure and Properties

Metals ◽  
2020 ◽  
Vol 10 (5) ◽  
pp. 635
Author(s):  
Oscar Ríos-Diez ◽  
Ricardo Aristizábal-Sierra ◽  
Claudia Serna-Giraldo ◽  
Jose A. Jimenez ◽  
Carlos Garcia-Mateo
Keyword(s):  
Mechanical Properties ◽  
Heat Treatment ◽  
Heat Treatments ◽  
Second Step ◽  
Austenite Formation ◽  
Transformation Kinetics ◽  
Carburized Steel ◽  
Cast Steels ◽  
Final Microstructure ◽  
Kinetics Of

Carburizing implies the existence of a carbon gradient from the surface to the core of the steel, which in turn will affect both the critical temperature for austenite formation and the kinetics of the bainitic transformation during the austempering treatment. Therefore, for future development of carbo-austempered steels with nanobainitic microstructures in the case, it is key to understand the effect of such carbon gradient has on the final microstructure and the mechanical properties reached by the heat treatments used. This work was divided into two parts, firstly two alloys with similar carbon content to those at the surface and center of the carburized steel were used to establish the optimal heat treatment parameters and to study bainite transformation kinetics by high resolution dilatometry. In a second step, a carburized alloy is produced and subjected to the designed heat treatments, in order to evaluate the microstructure and mechanical properties developed. Results thus obtained are compared with those obtained in the same carburized alloy after following the most common quench and temper treatment.

Influence of the Chemical Composition on the Ausferritic Transformation in Carbide-Free Bainitic Cast Steel

2014 ◽  
Vol 793 ◽  
pp. 85-91
Author(s):  
Alejandro D. Basso ◽  
Nicolás E. Tenaglia ◽  
Roberto Enrique Boeri ◽  
Juan M. Massone
Keyword(s):  
Chemical Composition ◽  
Cast Steel ◽  
Isothermal Transformation ◽  
The Other ◽  
Chemical Compositions ◽  
Transformation Kinetics ◽  
Continuous Cooling ◽  
Cast Steels ◽  
High Silicon ◽  
Kinetics Of

This work focuses on the study of the solid state transformations that take place during the austempering of high silicon carbide-free bainitic cast steels with different chemical composition. In order to get this objective three cast steel melts with different chemical compositions were produced, evaluating the influence of Cr, Mn, Ni, Al and Co. For each of these steels, samples were subjected to an austempering heat treatment at 340 oC varying the austempering time from 5 sec to 120 sec. The results show that small regions of free ferrite were obtained during continuous cooling from the austenitising to the austempering temperatures in unalloyed high silicon cast steels. At short austempering time (5 sec), the presence of a small fraction of ausferrite was observed. Austempering for 60 sec showed a larger amount of ausferrite. However, the ausferritic reaction is incomplete, and some martensite also was present, mainly located in last to freeze (LTF) zones. After an austempering of 120 sec, a fully ausferritic matrix was obtained. The addition of Cr and Mo avoided the initial precipitation of free ferrite, and lowered the isothermal transformation kinetics. On the other hand the use of Al and Co increase the presence of ferrite formed during continuous cooling and accelerates the kinetics of the ausferritic reaction.

Effect of Isothermal Holding Temperature on NGS Kinetics of Phosphorus and Temper Embrittlement

2007 ◽  
Vol 348-349 ◽  
pp. 549-552
Author(s):  
Jun Wang ◽  
Qing Fen Li ◽  
Er Bao Liu
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Isothermal Holding ◽  
Boundary Segregation ◽  
Temper Embrittlement ◽  
Solution Treatment ◽  
Grain Boundary Segregation ◽  
Solution Temperature ◽  
Kinetics Of ◽  
Holding Temperature

When failure occurs in material, it is often occurs by fracture along some grain boundaries and often by the micro-segregation of embrittling impurity to the grain boundaries. In the present work, the non-equilibrium grain-boundary segregation (NGS) kinetics of phosphorus and the temper embrittlement at the same solution treatment and different isothermal holding temperature in steel 2.25Cr1Mo are studied. The NGS kinetics curves of phosphorus at the same solution temperature （1050 oC ）and different isothermal holding temperature (540 oC and 600 oC) are given. Experimental results provide a direct evidence of NGS kinetic model and show that the grain boundary segregation concentrations of phosphorus for specimen isothermal holding at 540 oC are higher than those at 600 oC. The peak values of AES patterns of solute atoms for specimen isothermal holding at 540 oC are also higher than those at 600 oC. It is therefore concluded that the lower the isothermal holding temperature, the higher the segregation concentration of phosphorus at the grain-boundaries, and also the higher the degree of embrittlement.

Mechanical Behavior of a Shape Memory Polymer

2006 ◽  
Author(s):  
Xin Wu ◽  
Leonard Dauerman ◽  
Song Zhang ◽  
Xiao Qiao ◽  
Jose Mabesa
Keyword(s):  
Shape Memory ◽  
Shape Memory Polymer ◽  
Isothermal Holding ◽  
Strain Recovery ◽  
Control Mode ◽  
Plastic Behavior ◽  
Polymer Systems ◽  
Potential Applications ◽  
Number Of Cycles ◽  
Holding Temperature

In recent years shape memory effect in polymer systems has drawn great attention for its potential applications for MEMS and medical devices. In this paper, the visco-elastic and plastic behavior and strain recovery characteristics of a thermoplastic have been studied extensively. Creep deformation by compression was performed under load or displacement control mode, and under monotonic or cyclic loading. The strain recovery ratio of the shape memory polymer is found to be strongly affected by the deformation temperature, isothermal holding temperature and time, amount of forward strain and relaxation time, and the number of cycles of strain/recovery. The creep behavior of the material is modeled.

scholarly journals Microstructure and mechanical properties of as-cast and annealed high strength low alloy steel

2019 ◽  
Vol 8 (4) ◽  
pp. 1
Author(s):  
Bárbara Ferreira de Oliveira ◽  
Michel Picanço Oliveira ◽  
Luis Augusto Hernandez Terrones ◽  
Márcia Giardinieri de Azevedo ◽  
Leonardo Barbosa Godefroid
Keyword(s):  
Mechanical Properties ◽  
Hsla Steel ◽  
Cast Steel ◽  
High Strength ◽  
Calcium Content ◽  
Casting Process ◽  
Mechanical Tests ◽  
Solidification Structure ◽  
Microstructure And Mechanical Properties

This paper presents a study on the microstructure and mechanical properties of a microalloyed HSLA steel solidified by continuous casting process and annealed at 1100 °C for 1 hour. The techniques of confocal microscopy, scanning electron microscopy and hardness, tensile and Charpy mechanical tests were used. The results of this research showed that the microstructure of the sample in the as-received condition was mainly composed of acicular ferrite and aggregates of ferrite and carbides. Non-metallic inclusion characterization of as-cast steel showed that calcium content was not enough to modify the morphology of some aluminates. After thermal treatment, the initial microstructure was transformed into polygonal ferrite and pearlite. In both conditions, different types of precipitates were found, which were classified according to their distribution in the microstructure. The steel with solidification structure showed a higher tensile strength, but its application would be unlikely in components that require good impact strength.

scholarly journals Fracture Mechanisms in Steel Castings

2013 ◽  
Vol 13 (3) ◽  
pp. 88-91 ◽  
Author(s):  
Z. Stradomski ◽  
S. Stachura ◽  
G. Stradomski
Keyword(s):  
Cast Steel ◽  
Hot Cracking ◽  
Hadfield Steel ◽  
Fracture Mechanisms ◽  
Structural Factors ◽  
Low Carbon ◽  
High Carbon ◽  
Cast Steels ◽  
Steel Castings ◽  
Low Alloyed Steel

Abstract The investigations were inspired with the problem of cracking of steel castings during the production process. A single mechanism of decohesion - the intergranular one - occurs in the case of hot cracking, while a variety of structural factors is decisive for hot cracking initiation, depending on chemical composition of the cast steel. The low-carbon and low-alloyed steel castings crack due to the presence of the type II sulphides, the cause of cracking of the high-carbon tool cast steels is the net of secondary cementite and/or ledeburite precipitated along the boundaries of solidified grains. Also the brittle phosphor and carbide eutectics precipitated in the final stage solidification are responsible for cracking of castings made of Hadfield steel. The examination of mechanical properties at 1050°C revealed low or very low strength of high-carbon cast steels.

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