Ultrafine grained steels can be produced either by advanced thermomechanical processes or by severe plastic deformation strategies. Work hardening behavior of ultrafine grained duplex mediummn. Hruska faculty of mathematics and physics, charles university prague, czech republic j. It is found that, when the austenite is reduced to a fine. Friction stir welding of ultrafine grained interstitial free. Toughness of ultrafine grained ferritic steels fabricated. Surface integrity analysis when milling ultrafinegrained. Enhancing irradiation tolerance of steels via nanostructuring. Dobatkin et al ultrafine grained low carbon steels by severe plastic deformation tem contrast at the grain boundaries. Microstructure and mechanical properties of an ultrafine grained mediummn steel article pdf available in defect and diffusion forum 385. Alloy design is one of the first considered issues, while designing new steel with targeted mechanical properties. Austenite stability during nanoindentation of ultrafine and coarse grained aisi 304l stainless steels s.
Sadeghi 5 1, 2 department of materials engineering, faculty of engineering, shahrekord university, shahrekord. In this study, it was shown that retained austenite is the most beneficial microstructure constitution for enhancing the ductility. 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. Toughness of ultrafine grained ferritic steels fabricated by. Development of ultrafine grained austenitic stainless steels. Unfortunate polygonization process was mostly local and heterogeneous and effected significantly the work hardening for both steels. Introduction the fabrication of bulk materials with ultrafine grain sizes has attracted a great deal of attention over the past two decades because of the materials enhanced properties. View table of contents for ultrafine grained materials ii. Mechanical properties of the ultrafine grained ufg steels having mean grain sizes much smaller than 1 m were systematically shown from the original experimental data.
Ultrafine grained steels with grain sizes below about 1 um offer the prospect of high strength and high toughness with traditional steel compositions. The results show ultrafinegrained workpiece preserves its surface integrity against cutting parameters more than the asreceived material. Dynamic fracture toughness of the ultrafine grained if steels was investigated as a function of grain size by miniaturized charpy impact test. The tensile strength of these ultrafine grained dualphase steels can be increased by up to 200 mpa as compared to coarsegrained dualphase steels while maintaining uniform elongation values. The effects of carbon content, alloying additions, initial starting structures and processing parameters like heating and cooling rate on the mechanical.
Ultrafine grained structure development in steel with different initial. Ultrafinegrained steels with a grain size of about one micron offer the prospect of high strength coupled with high toughness among conventional steel compositions and are attracting the attention of researchers worldwide. Three types of ultrafine grained ufg low carbon steel were fabricated by equal channel angular pressing, and their microstructure and tensile properties were examined. Austenite stability during nanoindentation of ultrafine. Fabrication and tensile properties of ultrafine grained steels d. The term submicron structure refers to grain sizes between 100 nm and nm. Structural ultrafine grained steels obtained by advanced. After energetic research works since middle 1990s including big national projects.
Ultrafine grained steels with a grain size of about one micron offer the prospect of high strength coupled with high toughness among conventional steel compositions and are attracting the attention of researchers worldwide. X80 pipeline steel produced by tmcp has high strength and high toughness with ultrafine grain microstructure. Pdf ultrafine grained steels with grain sizes below about 1. Specific heat treatment of 90% cold rolled trip steel results in ultrafine grained reverted austenitic microstructure with mean grain size of about 1. Pdf microstructure and mechanical properties of an. Mar 16, 2012 the ultrafine grained duplex steels were fabricated by austenite reverted transformation annealing of the medium manganese steels after quenching or cold rolling. Effects of various second phases on deformation behaviors and mechanical properties of ufg steels were investigated. Austenite stability during nanoindentation of ultrafine and. The fatigue properties of ultrafine grain austenitic steel ufg1610, which has a 1. In the present study, an ultrafine grained ufg 304l stainless steel with the average grain size of 300 nm was produced by a combination of cold rolling and annealing.
Surface integrity analysis when milling ultrafinegrained steels. Development of ultrafine grained austenitic stainless. Ultrafine grained steels with grain sizes below about 1 um offer the prospect of high strength and high toughness with traditional steel. Recent trends in producing ultrafine grained steels article pdf available in journal of minerals and materials characterization and engineering 0205. A cciaio fabrication and tensile properties of ultrafine. Ultrafine grained materials ii proceedings of a symposium sponsored by the shaping and forming committee of the materials processing and manufacturing division mpmd and the mechanical behavior committee jt. Structural ultrafine grained steels b obtainey d advanced controlled rolling r gonzalez1, j garcia o 2, m barbes a 2, m quintana j 1, l verdeja f 2, j verdeja i 2 1. The microstructures were examined by scanning electron microscopy sem and transmission electron microscopy tem and xray diffraction xrd. The production of ultrafine grained steels by thermomechanical processing hodgson, peter, barnett, matthew, beladi, hossein and kelly, georgina 2002, the production of ultrafine grained steels by thermomechanical processing, in international conference on thermomechanical processing. The unique feature of grain refinement is that it is the only strengthening mechanism which also increases toughness. Research on formation conditions of the ultrafinegrained. Table 1 gives a summary of the various process techniques described above and the ferrite grain sizes obtained for the different bcc steels. Ultrafine grained steels with grain sizes below about 1 m offer the prospect of high strength and high toughness with traditional steel compositions.
The possibility of making microstructures in which bands of ultra fine ferrite uff grains act as. Ultrafine grained steels with relatively simple and plain chemical compositions, strengthened primarily by grain refinement, have great potential for replacing high strength low alloyed steels. Overview of processing, microstructure and mechanical. The phenomenon of ultrafine grain refinement effect by the existing.
Schoo of engineering l, panamerican university, mexico city 03920, mexico. Work hardening behavior of ultrafine grained duplex medium. Ecap processed ultrafine grained austenitic 316 steel. Low carbon ultrafine grained dual phase steels ubc. The formation of ultrafine grained steels is an area of intense research around the world. Characterization of defects in ultrafinegrained interstitial. This heatsoaking to above the ferriteaustenite transformation temperature and subsequent slow cooling generates a fine, regular ferriticpearlitic microstructure in the steel. Ultrafine grained steels with grain sizes below about 1. Superplasticity of ultrafine grained lowalloy steels. Ultrafinegrained ufg steels with different microstructural constitutions were fabricated through annealing of tempered and deformed martensite. The effects of carbon content, alloying additions, initial starting structures and processing parameters like heating and cooling rate on the mechanical properties have. As mentioned above, ultrafine grained steels can be produced by two main methods. The ultrafine grained duplex steels were fabricated by austenite reverted transformation annealing of the medium manganese steels after quenching or cold rolling.
Compared with the earlier studies on low carbon ultrafine grained bcc steels, song et al. Ecap processed ultrafine grained fm grade 91 steel sample set 3. There are a number of methods to produce grain sizes of approximately 1. Grain refinement and formation of ultrafinegrained microstructure in a low carbon steel under electropulsing volume 17 issue 8 yizhou zhou, wei zhang. Gbs and stabilizing ultrafinegrained and nanocrystalline structures 22.
Role of stressassisted martensite in the design of strong. 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. Among the spd techniques the accumulated plastic strains true strains required to obtain submicronsized grains are of the order of 34 using ecap and. Revealing the extrahigh ductility and toughness of micro. Normalised fine grained structural steels are traditionally produced by means of heat treatment, socalled normalising annealing, after rolling.
Ngan 5 1,2,3,4 department of materials engineering, isfahan university of technology, 8415683111, isfahan, iran. Yag laser welding under different welding conditions. A laboratory processing route was designed that involves coldrolling of a tempered martensite structure followed by a second tempering step to produce a fine grained aggregate of ferrite and. Hpt processed nanocrystalline fm grade 91 steel sample set 4. Study on the effect of laser welding parameters on the microstructure and mechanical properties of ultrafine grained 304l stainless steel. Ultrafine grained ufg steels with different microstructural constitutions were fabricated through annealing of tempered and deformed martensite. Ultrafine grained dualphase steels journal of ultrafine. Ultrafine grained steels with grain sizes below about 1 m offer the prospect of high strength and. Equal channel angular pressing of steels bcc, al alloys fcc and. The ufg steels performed very high strength that reached to 24 times of the starting materials having conventionally coarsegrained structures. Low carbon ultrafine grained dual phase steels ubc library. Friction stir welding fsw was applied to ultra lowcarbon interstitial free steels with mean grain sizes ranging from 0. Pdf recent trends in producing ultrafine grained steels.
The microstructure coarsens and the toughness worsens at the coarse grained cg haz. The results show that plates of a highalloyed cast trip steel can be cold rolled up to 90% of thickness reduction leading to high amount of martensite 80%. Ultrafine grained highalloyed austenitic trip steel. A laboratory processing route was designed that involves coldrolling of a tempered martensite structure followed by a second tempering step to produce a fine grained aggregate.
Mechanical properties of ultrafine grained steels processed. E t s i m o ovied, o university, oviedo 33004, spain. Recent trends in producing ultrafine grained steels. A plain if steel and a padded if steel having various ultrafine grain sizes from 0. 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.
Pdf recent progress in grain refinement of steels was overviewed. In this study, it was shown that retained austenite is the most beneficial microstructure. Characterization of defects in ultrafinegrained interstitialfree steel prepared by severe plastic deformation j. It is found that, when the austenite is reduced to a fine scale of about 300 nm, the initial deformationinduced microstructure can be dominated by parallel lamellae of. Issue 1 structural ultrafine grained steels obtained by advanced controlled rollin 63 g name s315 s355 s420 s460 s500 s550 s600 s650 s700 table 1 chemical composition of thermomechanically rolled steels material number 1. Ufg ferritepearlite steels with or without vanadium exhibited ultrahigh strength, almost three times compared to that of their coarse grained counterparts. 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. Dobatkin et al ultrafinegrained low carbon steels by severe plastic deformation tem contrast at the grain boundaries. The development of ultrafine grained structures in 316l and 304type austenitic stainless steels subjected to large strain cold working and subsequent annealing and their effect on mechanical properties were studied. Application of these ultrafinegrained steels to potential engineering structures demands extensive study of their mechanical properties. 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. These materials are currently the subject of extensive research efforts worldwide. Recently, new pipeline steels have been proposed to resist extrahigh ductility and toughness of the microduplex mediummn steel process, thus the carbon content in the austenite 0. The present work deals with grain refinement of medium carbon steel, having different initial microstructure, modified by either thermal andor thermomechanical.
Enhancing irradiation tolerance of steels via nanostructuring by innovative manufacturing techniques haiming wen idaho state university. Grain refinement and formation of ultrafinegrained microstructure in. In general, the term ultrafine grain is used for average grain sizes between 1. The formation of ultrafine grained steel microstructures. Taguchi experimental design was used to optimize the effect of frequency, welding time, laser current. Journal of ultrafine grained and nanostructured materials, 49, 2, 2016, 120127. References journal of ultrafine grained and nanostructured.
Gubicza department of materials physics, eotvos lorand university, budapest, hungary h. Fracture toughness of the ultrafine grained lowalloy steel at low temperature borisova maria, yakovleva sofia, makharova susanna institute of physicaltechnical problems of the north, siberian branch of the ras, russian federation abstract severe plastic deformation is a well known procedure for fabrication considerable grain refinement in metal. An investigation on mechanical properties of ultrafine. Ultrafine grained steels and the n coefficient of strain. The rather narrow processing window necessary to obtain these properties was evaluated by determining the effect of intercritical annealing conditions on. An investigation on mechanical properties of ultrafine grained 316 stainless steel by thermomechanical treatment h. The cold rolling was accompanied by a mechanical twinning and a partial martensitic transformation and resulted in the development of elongated austeniteferrite.
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