In general, the term ultrafine grain is used for average grain sizes between 1. Based on systematic description of research achievements of the project of ultrafine grain steels and their engineering applications, new theories of microstructural refinement and the newly developed technologies in production of high strength and high toughness steels are introduced. As this effect, however, has not yet been investigated in steels, fatigue experiments of an unalloyed medium carbon steel with a carbon content of 0. In contrast to the typical ductiletobrittle transition behavior of bodycentered cubic bcc steels, we. The microstructure coarsens and the toughness worsens at the coarse grained cg haz. Martensite phase reversioninduced nano ultrafine grained. The phenomenon of ultrafine grain refinement effect by the existing. These materials are currently the subject of extensive research efforts worldwide. Laser welding and arc welding processes of 400 mpa grade ultrafine grained carbon steel and 800 mpa grade ultrafine microstructure bainitic steel. Ultrafine grained ufg steels with different microstructural constitutions were fabricated through annealing of tempered and deformed martensite.
In this study, it was shown that retained austenite is the most beneficial microstructure. This paper provides an overview on obtaining lowcarbon ultrafine grained dualphase steels through rapid intercritical annealing of coldrolled sheet as improved materials for automotive applications. Microstructure and mechanical properties of a coldrolled. Pdf recent trends in producing ultrafine grained steels. Surface integrity analysis when milling ultrafinegrained. Ultrafine grained steels with grain sizes below about 1 um offer the prospect of high strength and high toughness with traditional steel. Ultrafine grained steels and the n coefficient of strain. Pdf formability of ultrafinegrained interstitialfree. Salvatori on the wake of the advances in australia and japan in achieving even finer grain sizes, the european steel companies became particularly interested in the prospects for 1 mmuff.
A new processing route to produce ultrafine grained dualphase steel has been proposed, involving coldrolling and subsequent intercritical annealing of a fibrous ferritemartensite starting structure. Pdf ultrafine grained steel by innovative deformation. Properties of finegrained steels generated by displacive. Ultrafine grained dp ufgdp steel with an average ferrite grain size of about 2. The possibility of making microstructures in which bands of ultra fine ferrite uff grains act as.
Structural ultrafine grained steels obtained by advanced. Production ultrafine grained steels by heat treatment. Effects of various second phases on deformation behaviors and mechanical properties of ufg steels were investigated. Pdf improvement of the work hardening rate of ultrafine. The microstructure coarsens and the toughness worsens at the coarse grained. The formation of ultrafine grained steels is an area of intense research around the world. Recent trends in producing ultrafine grained steels article pdf available in journal of minerals and materials characterization and engineering 0205. Ultrafine grained steels managing both high strength and. Recent trends in producing ultrafine grained steels. Friction stir welding fsw was applied to ultra lowcarbon interstitial free steels with mean grain sizes ranging from 0. Dynamic transformation mechanism for producing ultrafine. A coarse grained cg sample demonstrated high formability with an erichsen index ei of 4. Ultrafine grained steels with grain sizes below about 1 m offer the prospect of high strength and high toughness with traditional steel compositions. Mechanical properties of the ultrafine grained ufg steels having mean grain sizes much smaller.
A tiadded ultralowcarbon interstitial free if steel was. On the other hand, it has become recently possible to fabricate the steels with ultrafine grained ufg structures of which mean grain size is smaller than 1 m, at least in laboratory scales 2. The term submicron structure refers to grain sizes between 100 nm and nm. Superplasticity of ultrafine grained lowalloy steels. Friction stir welding of ultrafine grained interstitial free steels.
The stretch formability of ultrafine grained ufg interstitial free steel if steel produced by equalchannel angular extrusionpressing ecaep via various strain paths was investigated with a miniaturized erichsen test. Dynamic fracture toughness of the ultrafine grained if steels was investigated as a function of grain size by miniaturized charpy impact test. In general, the term ultrafine grain is used to define microstructures with grain sizes between 100 nm and nm, whereas the term nano structure refers to grain sizes below 100 nm. Microstructure and mechanical properties of ultrafine. Friction stir welding of ultrafine grained if and carbon steels shielding gas was used during the friction stir welding of the steels, as shown in fig. Fabrication and tensile properties of ultrafine grained steels d. A plain if steel and a padded if steel having various ultrafine grain sizes from 0. Pdf ultrafine grained steels with grain sizes below about 1.
Ultrafine grained steels managing both high strength. An investigation on mechanical properties of ultrafine. A further high potential area of ultrafine grained steels is the domain of high strain rate superplasticity at medium and elevated temperatures 14. Dobatkin et al ultrafine grained low carbon steels by severe plastic deformation tem contrast at the grain boundaries. Overview of processing, microstructure and mechanical. While several reports presented tensile properties of ultrafine grained steels 14, corresponding charpy impact properties were rarely investigated due to limitations in sample size typically available from such laboratoryscale process setups. However, this treatment enhances the multipotent mesenchymal stromalstem cell proliferation by 26% for 316l steel and by 17% for crniti. Open access related content fatigue behavior of ultrafine. Alloy design is one of the first considered issues, while designing new steel with targeted mechanical properties.
It is well knownthat the refinement of grainsize inmetals leads toa significant improvement inspecific mechanical properties. Strength and ductility of ultrafine grained aluminum and. Table 1 gives a summary of the various process techniques described above and the ferrite grain sizes obtained for the different bcc steels. Pdf microstructure and corrosion properties of ultrafine. In the current study, the formation of nano ultrafine grained austenitic microstructure in a microalloyed aisi 304l stainless steel was investigated by the advanced. Hydrogen embrittlement of ultrafine grained austenitic stainless steels 27 the second one, crnimo stainless steel aisi 316ltype, possesses stable austenitic structure due to rather high sfe 24.
Second phase precipitation in ultrafine grained ferrite steel theoretically estimated in 1. Formability of ultrafine grained interstitial free steels article pdf available in metallurgical and materials transactions a 449 september 20 with 273 reads how we measure reads. Improvement of the work hardening rate of ultrafine grained steels through second phase particles. Tensile tests of the hotrolled aods steel samples showed yield. Microstructure evolution in ultrafinegrained interstitial. Structureproperties relationship of ultrafine grained vmicroalloyed dual phase steels babak shalchi amirkhiz 1, colin scott 1, fateh fazeli 1. Strain induced dynamic transformation and ultrafine surface grained steel one of the objectives of this project was to obtain ultra fine surface grained steels for plain and microalloyed lowc steels 0. The base metal of the ultrafine grained twip steel shows high strength and adequate uniform elongation 35%, although it was reported that the ultrafine grained interstitial free if steels and aluminums have limited ductility with ultimate high strength 6. Pdf recent progress in grain refinement of steels was overviewed. A cciaio fabrication and tensile properties of ultrafine. Grain refinement is an effective method to improve strength and toughness simultaneously without addition of alloying elements. Toughness of ultrafine grained ferritic steels fabricated. Second phase precipitation in ultrafinegrained ferrite steel.
Furthermore, ultrafine grained steels ufg may be applied in the future in most of the steel markets and can be used in other industrial applications, such as the ones that require superplastic behavior, just as this work demonstrates. Strength and ductility of ultrafine grained ufg aluminum and iron fabricated by arb and annealing were clarified in the grain sizes ranging from 200 nm to 20. Canmetmaterials natural resources canada, hamilton, canada the effect of vanadium microalloying on ultrahigh strength dual phase dp ferritemartensite steel microstructure and was studied using tem. Fracture toughness characteristics of ultrafine grained nb. X80 pipeline steel produced by tmcp has high strength and high toughness with ultrafine grain microstructure. Formability of ultrafinegrained interstitialfree steels. Dynamic transformation mechanism for producing ultrafine grained steels article pdf available in advanced engineering materials march. In this study, the mechanical properties of an ultrafine grained 0. Ultrafine grained high carbon steel by innovative deformation.
The significantly altered cyclic stability under combined thermalmechanical loading is attributed to localized grain growth. They observed that the annealing time and temperature had a significant effect on the final grain size of the coldworked stainless steel samples. Strength held hallpetch relationship, while uniform elongation of the ufg materials was limited below a. Grain refinement is an effective way to improve both strength and. Kim three types of ultrafine grained ufg low carbon steel were fabricated by equal channel angular pressing, and their microstructure and tensile properties were examined. Cyclic stability of ultrafinegrained interstitialfree. The biocompatibility of samples with the ultrafine grain structure obtained in the ecap process did not deteriorate in comparison with an austenitic 316l stainless steel in coarse. Ultrafine grained steels by advanced thermomechanical processes and severe plastic deformations i. Friction stir welding of ultrafine grained twip steel. Schoo of engineering l, panamerican university, mexico city 03920, mexico. Friction stir welding of ultrafine grained if and carbon. The fatigue performance of an ultrafine grained interstitial free steel was investigated at elevated temperatures up to a homologous temperature of 0. Among the spd techniques the accumulated plastic strains true strains required to obtain submicronsized grains are of the order of 34 using ecap and. In order to obtain ultrafine grains in steels, several new.
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