Demonstration of Elemental Partitioning During Austenite Formation in Low-Carbon Aluminium alloyed steel

This work investigates the influence of aluminium, in solid solution, on austenite formation in a lowcarbon aluminium alloyed (0.48 wt. %) steel during continuous heating. A thin section across an untransformed ferrite and austenite interface was prepared for transmission electron microscopy by focused ion beam milling. Microstructural characterization using imaging and elemental analysis demonstrates that aluminium partitions from austenite to ferrite during very slow heating conditions, stabilizing this latter phase and shifting the final transformation temperature for austenite formation (Ac3)Peer reviewe

Demonstration of Elemental Partitioning During Austenite Formation in Low-Carbon Aluminium alloyed steel

This work investigates the influence of aluminium, in solid solution, on austenite formation in a lowcarbon aluminium alloyed (0.48 wt. %) steel during continuous heating. A thin section across an untransformed ferrite and austenite interface was prepared for transmission electron microscopy by focused ion beam milling. Microstructural characterization using imaging and elemental analysis demonstrates that aluminium partitions from austenite to ferrite during very slow heating conditions, stabilizing this latter phase and shifting the final transformation temperature for austenite formation (Ac3)Peer reviewe

The effect of deliberate aluminium additions on the microstructure of rolled steel plate characterized using EBSD

The use of aluminium as a deliberate alloying addition in steels has attracted increased attention recently as a possible replacement for Si in transformation-induced plasticity (TRIP) steels. In addition, some authors have suggested that it offers beneficial effects as a solid solution strengthener as well as galvanizability. In this work three low carbon (0.02 wt.%) manganese (1.4 wt.%) steels have been alloyed with very different aluminium contents (0.02, 0.48 and 0.94 wt.%) in order to study the effect of this alloying element on the final ferritic microstructure. Two different rolling schedules have been applied to these steels and the final microstructures have been characterized extensively by EBSD measurements. The results indicate that aluminiumadditions have a profound influence on ferrite grain size and the grain boundary misorientation distribution functionsPeer reviewe

Understanding the effect of aluminium on the microstructure on low level nitrogen steel

Aluminium has been used as a de-oxidant and grain refiner element for more than 100 years, however, the use of aluminium as a deliberate alloying addition in steels has attracted increased attention recently as a possible replacement for Si in Transformation Induced Plasticity (TRIP) steels. Although the effect of substitutional elements such as manganese and chromium has been investigated in detail in the last few decades, there has been little research concerned with the effect of Al as a substitutional element in steel in amounts higher than 0.1 wt%. This could be due to the previous lack of industrial interest and also technological concerns over the production of high Al-content steels. Work was carried out on three low carbon (0.02 wt%) manganese (1.4 wt%) steels with very low levels of nitrogen (10 ppm) which have been alloyed with very different aluminium contents (0.02, 0.48 and 0.94 wt%). Electron back scatter diffraction (EBSD) was employed to study the effect of excess aluminium (apart from aluminium nitride) on the final ferritic microstructure. In order to have a better understanding in relation to the role of excess aluminium in ferritic microstructure it required an investigation of the austenite to ferrite transformation. Prior to investigation of the influence of aluminium on austenite to ferrite transformation, attempts were made to reveal the role of excess aluminium in austenite formation. The results obtained from the latter part of the research enabled the author to better understand the role of excess aluminium in austenite grain formation and growth. From this study, it may be concluded that excess aluminium has a significant influence on as rolled ferritic structure which could be the result of changes in austenite to ferrite transformation kinetics. In addition, the results obtained from this research show a significant effect of excess aluminium on austenite formation and growth

Evaluation of microstructures and mechanical properties of deltha trip steel with different vanadium contents

This research studies the effect of adding 0.12 and 0.25 wt% vanadium on the microstructure and mechanical properties of a delta-TRIP steel. Optical microscopy and scanning electron microscope (SEM) were employed to investigate the microstructure of the steel. In addition, hardness measurements and tensile testing were used for the evaluation of the mechanical properties. The X-ray diffraction (XRD) analysis was also applied to analyze the present phases. The structure of the three studied steels before applying the heat treatment cycle consisted of delta-ferrite, allotriomorphic ferrite, martensite, and pearlite. The heat treatment cycle led to the stability of the austenite phase. The addition of 0.12 wt% V resulted in the enhancement of the mechanical properties so that the best combination of strength (866 MPa) and elongation percentage (41 %) was achieved in this steel. Nonetheless, the addition of 0.25 wt% V deteriorated the mechanical properties since the increase in the vanadium content promoted the formation of martensite, decreased the percentage of the retained austenite, and weakened the mechanical properties. However, adding 0.12 wt% V improved the mechanical properties since it increased the strength through solid-solution strengthening and precipitation hardening; no brittle martensite was formed, and lamellar δ-ferrite was achieved. The steel containing 0.12 wt% V, exhibiting a formability index of 35.7 GPa%, is in the range of the third-generation advanced high-strength steels

Effect of milling time on XRD phases and microstructure of a novel Al67Cu20Fe10B3 quasicrystalline alloy

The quasicrystalline materials represent a new materials group with definite crystallite structural characteristics, in which the AlCuFe(B) quasicrystalline alloys have been widely studied owing to its various technological advantages such as easily accessible in nature, thermal stability, affordability as well as not having toxic constituent elements. Although these materials can be achieved by different procedures, the synthesis of more extensive amounts of AlCuFeB quasicrystalline single-phase powders is more complicated. In this study, the Al _67 Cu _20 Fe _10 B _3 quasicrystalline alloys were synthesized through the mechanical alloying process and afterward consolidated to the bulk specimens by cold isostatic pressing (CIP) technique. The structural and microstructural evolutions, as well as the morphology of as-milled powders and phase transformations, were studied during the ball milling process using field-emission scanning electron microscopy (FESEM) and x-ray diffractometry (XRD), while the thermal behavior was investigated using differential thermal analysis (DTA). The most fascinated result revealed that the stable AlCuFeB single quasicrystalline phase could be directly synthesized in short milling times (around ∼4 h) by a high-energy planetary ball milling. It was appreciated that the icosahedral phase is stable up to 300 °C, which is misplaced stability at superior temperatures and transforms into crystalline phases. The microhardness of consolidated ball-milled powders at various milling times was determined and it was figured out that the icosahedral phase has an extreme microhardness as much as 10.73 GPa

The Influence of La and Ce Addition on Inclusion Modification in Cast Niobium Microalloyed Steels

The main role of Rare Earth (RE) elements in the steelmaking industry is to affect the nature of inclusions (composition, geometry, size and volume fraction), which can potentially lead to the improvement of some mechanical properties such as the toughness in steels. In this study, different amounts of RE were added to a niobium microalloyed steel in as-cast condition to investigate its influence on: (i) type of inclusions and (ii) precipitation of niobium carbides. The characterization of the microstructure by optical, scanning and transmission electron microscopy shows that: (1) the addition of RE elements change the inclusion formation route during solidification; RE > 200 ppm promote formation of complex inclusions with a (La,Ce)(S,O) matrix instead of Al2O3-MnS inclusions; (2) the roundness of inclusions increases with RE, whereas more than 200 ppm addition would increase the area fraction and size of the inclusions; (3) it was found that the presence of MnS in the base and low RE-added steel provide nucleation sites for the precipitation of coarse niobium carbides and/or carbonitrides at the matrix–MnS interface. Thermodynamic calculations show that temperatures of the order of 1200 °C would be necessary to dissolve these coarse Nb-rich carbides so as to reprecipitate them as nanoparticles in the matrix.We acknowledge support by the CSIC Open Access Publication Initiative through its Unit of Information Resources for Research (URICI).The authors from the University of Tehran gratefully acknowledge the financial support provided by the Office of International Affairs and the Office for Research Affairs, College of Engineering, for the project number 8107009.6.34. The authors from Centro Nacional de Investigaciones Metalúrgicas (CENIM) that belong to the Consejo Superior de Investigaciones Científicas (CSIC) would like to acknowledge the financial support from Comunidad de Madrid through the project Diseño Multiescala de Materiales Avanzados (DIMMAT-CM_S2013/MIT-2775). Javier Vivas acknowledges financial support in the form of a FPI (Formación de Personal Investigador) Grant BES-2014-069863. Authors are grateful to the Phase Transformations and Microscopy labs from CENIM-CSIC and to the Centro Nacional de Microscopia Electronica (CNME), located at Complutense Metals 2017, 7, 377 16 of 17 University of Madrid (UCM), for the provision of laboratory facilities. Mr. Javier Vara Miñambres from the Phase Transformations lab (CENIM-CSIC) is gratefully acknowledged for their continuous experimental suppor

Application of Nomarski Differential Interference Contrast Microscopy to Highlight the Prior Austenite Grain Boundaries Revealed by Thermal Etching

Revealing prior austenite grain boundaries by thermal etching has been demonstrated to be a reliable and fast method compared to chemical etching for microalloyed carbon steels. However, sometimes visualization of the thermally etched prior austenite grain boundaries is hindered by the presence of grain boundaries of other phases (e.g. ferrite and/or pearlite) which are thermally etched during slow cooling from high temperature. This work shows that, under these conditions, the use of Nomarski differential interference contrast microscopy under bright field illumination helps to highlight the thermally etched prior austenite grain boundariesMinisterio de Ciencia e Innovación (Proyecto Petri PET2007_0326_02)Peer reviewe

Contributions of Rare Earth Element (La,Ce) Addition to the Impact Toughness of Low Carbon Cast Niobium Microalloyed Steels

In this research Rare Earth elements (RE), La and Ce (200 ppm), were added to a low carbon cast microalloyed steel to disclose their influence on the microstructure and impact toughness. It is suggested that RE are able to change the interaction between the inclusions and matrix during the solidification process (comprising peritectic transformation), which could affect the microstructural features and consequently the impact property; compared to the base steel a clear evolution was observed in nature and morphology of the inclusions present in the RE-added steel i.e. (1) they changed from MnS-based to (RE,Al)(S,O) and RE(S)-based; (2) they obtained an aspect ratio closer to 1 with a lower area fraction as well as a smaller average size. Besides, the microstructural examination of the matrix phases showed that a bimodal type of ferrite grain size distribution exists in both base and RE-added steels, while the mean ferrite grain size was reduced from 12 to 7 μm and the bimodality was redressed in the RE-added steel. It was found that pearlite nodule size decreases from 9 to 6 μm in the RE-added steel; however, microalloying with RE caused only a slight decrease in pearlite volume fraction. After detailed fractography analyses, it was found that, compared to the based steel, the significant enhancement of the impact toughness in RE-added steel (from 63 to 100 J) can be mainly attributed to the differences observed in the nature of the inclusions, the ferrite grain size distribution, and the pearlite nodule size. The presence of carbides (cementite) at ferrite grain boundaries and probable change in distribution of Nb-nanoprecipitation (promoted by RE addition) can be considered as other reasons affecting the impact toughness of steels under investigation.The authors from University of Tehran gratefully acknowledge the financial support provided by the office of international affairs and the office for research affairs, college of engineering, for the Project Number 8107009.6.34. The authors from CENIM-CSIC would like to acknowledge the financial support from Comunidad de Madrid through DIMMAT-CM_S2013/MIT-2775 Project. Authors are grateful to the Phase Transformations and Microscopy labs from CENIM-CSIC. Mr. Javier Vara Miñambres from the Phase Transformations lab (CENIM-CSIC) is gratefully acknowledged for his continuous experimental support.Peer Reviewe