Wt Pct Si Research Articles

Effect of Boron on the Interfacial Heat Transfer, Contact Behavior, and Microstructure in the Simulation of Strip Casting of 3.5 Wt Pct Si Non-oriented Silicon Steel

Effect of Boron on the Interfacial Heat Transfer, Contact Behavior, and Microstructure in the Simulation of Strip Casting of 3.5 Wt Pct Si Non-oriented Silicon Steel

CALPHAD-Based Modeling and Experimental Validation of Silicon Effect on the Solidification Behavior of Novel SiNb Cast Irons

The low oxidation resistance of SiMo ductile cast irons used as exhaust manifold material at high temperatures necessitates the development of new generation ductile cast iron compositions. New alloy designs can be made using CALPHAD methodology, and solidification sequence, segregation and critical phase transformation temperatures can be determined, especially for the solidified bulk materials. Thus, in commercial practicality, castable compositions with a raised A1 temperature can be obtained. In this study, novel SiNb cast irons with varying silicon contents were developed as candidate materials for exhaust manifolds. Solidification sequence, microsegregation, phase transformations, equilibrium phases of hypereutectic compositions containing 4 to 7 wt pct Si were calculated by CALPHAD-based modeling. The bulk materials of the studied compositions were cast as Y blocks and metallurgical analyzes were carried out. Studies revealed that; (i) in the ferritic matrix of the cast irons, graphite, Nb-rich carbides and some pearlite existed, (ii) pearlite formation was due to the negative segregation of silicon and positive segregation of manganese during solidification, (iii) as silicon content increased the amount of silicon dissolved in ferrite phase increased in the solidified structure and as a result pearlite formation decreased at the cell boundaries, and amount of vermicular graphite increased, (iv) depending on the silicon content the critical A1 temperature varied between 860 °C to 1013 °C and these values were higher than that of SiMo cast iron. All these findings revealed that SiNb cast irons had phase stability at higher temperatures compared to SiMo cast iron.

The Growth of {1 1 h}〈1 2 1/h〉 (α*-Fiber) Grains and the Evanesce of {001}〈100〉 (Cube) Grains During the Recrystallization of Warm Rolled Fe-6.5 Wt Pct Si Non-oriented Electrical Steel

The Growth of {1 1 h}〈1 2 1/h〉 (α*-Fiber) Grains and the Evanesce of {001}〈100〉 (Cube) Grains During the Recrystallization of Warm Rolled Fe-6.5 Wt Pct Si Non-oriented Electrical Steel

Effect of Superheat on the Initial Solidification Behaviors of 3.5 wt pct Si Non-oriented Electrical Steel During Strip Casting

Effect of Superheat on the Initial Solidification Behaviors of 3.5 wt pct Si Non-oriented Electrical Steel During Strip Casting

Investigation of Cracking Behavior of Fe–6.7 Wt Pct Si Manufactured Using Laser Powder Bed Fusion

Investigation of Cracking Behavior of Fe–6.7 Wt Pct Si Manufactured Using Laser Powder Bed Fusion

Preparation of C54-TiSi2 by the Electromagnetic Directional Solidification of Hypoeutectic Ti-53.98 Wt Pct Si Alloy Melt

Preparation of C54-TiSi2 by the Electromagnetic Directional Solidification of Hypoeutectic Ti-53.98 Wt Pct Si Alloy Melt

Microstructure and Magnetic Properties of 6.5 Wt Pct Si Steel Strip Produced by Simulated Strip Casting Process

An improved dip test apparatus was used to simulate the strip casting of 6.5 wt pct Si steel in this study. The results showed that the interfacial heat flux between melt and substrate could reach maximum value of 8.2 MW/m2, with > 4350 kJ/m2 heat being removed in the first 1.0 s. The as-cast strip mainly consisted of large columnar grains hundreds of microns in length. The high cooling rate of the as-cast strip suppressed the formation of ordered phases and the precipitation of elements. Only several complex particles of MnS-TiN of a few nanometers were found. After annealing at 1273 K (1000 °C) for 30 minutes, a large number of small particles such as TiN precipitated from the ferrite matrix. Within the testing frequency and magnetic field strength, the three strip samples obtained at different conditions showed the lowest iron loss at the frequency of 20 kHz and the magnetic field strength of 0.07 T, which were 22, 18 and 17 W/kg, respectively. The coercive force and iron loss decreased with increasing heat treatment temperature, while the magnetic permeability showed the opposite pattern. The magnetic permeability and iron loss of the silicon steel strip produced by strip casting are comparable to those of the silicon steel products produced by other techniques such as melt spinning and conventional rolling.

Thermomechanical Processing Map in Retaining {100}//ND texture via Strain-Induced Boundary Migration Recrystallization Mechanism

The feasibility of establishing thermomechanical conditions to promote {100}//ND fiber texture via strain-induced boundary migration (SIBM) recrystallization mechanism in a non-grain oriented (NGO) electrical steel was investigated. Single-hit uniaxial compression at various temperatures and strains has been applied on Fe-6 wt pct Si to establish the relationship between stored energy and the softening mechanisms. Recovery only and recrystallization by SIBM or by subgrain growth (SGG) have been observed depending on the stored energy level. A strong {100}//ND fiber recrystallization texture, i.e., 45 pct area fraction, was seen in the sample which was deformed to 0.2 strain at 650 °C and then annealed at 1000 °C for 15 minutes, whereas only 13 pct {100}//ND fiber component was observed after 0.4 strain at 500 °C followed by the same annealing treatment. By examining the same microstructural region before and after annealing via EBSD, it has been shown that {100}//ND textured recrystallized grains were formed adjacent to the {100}// ND textured deformed matrix. Low stored energy has been shown to favor the formation of {100}//ND texture recrystallized grains via SIBM recrystallization mechanism attributed to its slow recrystallization nucleation rate. The results from the deformation studies have been used to suggest a processing window map concept to define the recovery, SIBM, and SGG regions for the starting as-cast columnar microstructure.

Hot Tearing Behavior in Double Ternary Eutectic Alloy System: Mg-Ce-Al Alloys

The hot tearing behavior of the double ternary eutectic alloy system, Al-6Mg-xSi (0 to 6.0 wt pct Si) alloys, was evaluated by a constrained rod casting mold equipped with a thermocouple and a load cell connected to a data acquisition system. Experimental results were compared with the results calculated by Scheil’s model using Pandat software to predict the occurrence of hot tearing in Al-6Mg-xSi alloys. The curve of hot tearing susceptibility contained two peaks, which were mainly affected by the double ternary eutectic reactions and the solidification phases evolution. And it agreed with the Kou’s hot tearing index precisely. The types and fractions of solidification phases (Al3Mg2, Mg2Si, and eutectic Si) determined by the addition of Si content changed the freezing range and eutectic liquid fraction greatly. In addition, the types, fractions, sizes, and distributions of solidification phases affected the nucleation, propagation, and healing of hot tear cracks. The maximum contraction force value decreased as the reduction of volume shrinkage coefficient due to the addition of Si content. The drop-in force value on the contraction force curve could indicate the occurrence of hot tearing, and predict the hot tearing susceptibility when considering the shrinkage coefficient.

Mechanism for Si Poisoning of Al-Ti-B Grain Refiners in Al Alloys

Al-5Ti-1B is the most widely used grain refiner for Al alloys. However, it is not effective for grain refining Al alloys containing more than 3 wt pct Si. This adverse effect of Si is referred to as Si poisoning. In spite of extensive experimental and theoretical investigations in the past decades, the exact mechanism for Si poisoning is still not clear. In this work, the state-of-the-art electron microscopy was performed to investigate the mechanism for Si poisoning. Our experimental results suggest that Si segregates preferably to the TiB2/Al-Si melt interface and the pre-existing Al3Ti 2-dimensional compound (2DC) layer on TiB2 surface dissolves into the Al-Si melt. Based on the experimental results, we have postulated a new mechanism for Si poisoning: interfacial segregation of Si leads to enrichment of Si at the TiB2/Al-Si melt interface, and this in turn makes the pre-existing Al3Ti 2DC on the TiB2 surface unstable and dissolve gradually in the melt, resulting in a loss of TiB2 nucleation potency and hence a decreased total number of potent TiB2 particles available for heterogeneous nucleation and grain initiation and consequently an increased grain size. This mechanism for Si poisoning can explain consistently the experimentally observed phenomenon reported in the literature.

Effects of Si Content and Forging Pressure on the Microstructural and Mechanical Characteristics in Semi-solid Forging of Al-Si-Mg Alloys

In this study, semi-solid forging (SSF) using electromagnetic stirring of Al-Si-Mg alloys was carried out. To evaluate the acceptability for producing a semi-solid slurry of an alloy with various Si contents, the temperature sensitivity of the solid fraction and solidification range were calculated by Thermo-Calc. The effects of the Si content and forging pressure on the microstructural and mechanical properties, such as tensile strength and elongation, were ascertained. Specimens were taken from two typical positions on the semi-solid-forged products, where one position corresponds to a region of directly applied forging pressure and the other region corresponds to the position of slurry being squeezed and extruded. Microstructural characteristics such as average grain size, volume fraction, and form factor of the α-Al were evaluated as the Si content was changed from 5 to 7 wt pct at 0.5 wt pct intervals. As the Si content increased, the particle size of α-Al and tensile strength increased, while the volume fraction of α-Al and elongation decreased. At lower Si contents, solidification shrinkage was observed, resulting in a decrease in the elongation. At 5 and 6 wt pct Si, α-Al particles were agglomerated, and shrinkage was observed. Uniform, fine, and globular microstructures were obtained at 6 wt pct Si. At 6 and 7 wt pct Si, α-Al particles were coarsened. The forging pressure was changed from 100 to 250 MPa, and at a forging pressure of 250 MPa, shrinkage was observed. As the forging pressure was increased from 100 to 200 MPa, the tensile strength and elongation increased, and the particle size of α-Al decreased. At a forging pressure of 250 MPa, α-Al particles were deformed and agglomerated, which decreased the strength.

Texture Evolution of a 2.8 Wt Pct Si Non-oriented Electrical Steel and the Elimination of the 〈111〉//ND Texture

A 2.8 wt pct Si non-oriented electrical steel was thermomechanically processed using conventional hot rolling, hot band annealing, cold rolling and final annealing routes. The evolution of texture during these processes was investigated using electron backscatter diffraction (EBSD) techniques. The final annealing was conducted at 750 °C for various times (10 to 120 minutes), and it was found that by simply changing the annealing time, the texture shows significantly different features, i.e. depending on the annealing time, the Goss ({011}〈100〉), the θ-fiber (〈001〉//normal direction, ND) or the γ-fiber (〈111〉//ND) may dominate the texture. Annealing for 60 or 90 minutes can essentially eliminate the magnetically unfavorable 〈111〉//ND texture while promoting the desired 〈001〉//ND texture. On the other hand, annealing at the same temperature for 30 or 120 minutes, the 〈111〉//ND texture is strengthened and the favorable 〈001〉//ND texture is weakened. The formation of the typical textures observed in each process was examined with respect to known mechanisms existing in the literature. The formation of the various textures during annealing at different times was discussed against the oriented growth theory based on a statistic analysis of the grain boundary misorientation and grain size. It is seen that during annealing at different times, the grain boundary character (e.g. mobility) and the grain size may determine the growth of certain orientations, which give rise to the different textures after annealing for different times.

Development of Through-Thickness Cube Recrystallization Texture in Non-oriented Electrical Steels by Optimizing Nucleation Environment

Texture evolution of 2.1 wt pct Si non-oriented electrical steel sheets was investigated using macro- and micro-texture analysis. The desirable cube ({001}〈100〉) component successfully dominates the recrystallization texture through sheet thickness. The nucleation sites of cube grains are mainly identified at the interfaces of {001}〈230〉-{001}〈130〉 and {223}〈362〉-{114}〈481〉 oriented deformation bands. The formation of through-thickness cube recrystallization texture can be attributed to the optimization of nucleation environment, featuring quantitative advantage of cube nuclei at both strong plane strain and strong shear strain layers under the superiority of locally low density of cube nuclei.

Microstructure Solidification Maps for Al-10 Wt Pct Si Alloys

Hypo-eutectic Al-Si alloys are widely used in both the automotive and aerospace industries; however, they still have limited usage as structural materials, due to the inherent morphology of the Si phase that forms within the eutectic structure. This non-ideal Si morphology can be modified, via alloy additions and/or rapid solidification (RS), but the underlying mechanism(s) behind this is poorly understood. This work focused on understanding the influence of RS on the eutectic structure, for hypo-eutectic Al-10 wt pct Si alloys produced by Impulse Atomization and Differential Scanning Calorimetry. This study found that the eutectic Si forms into four distinct morphologies: (1) flaky, (2) fibrous, (3) globular + fibrous and (4) globular, depending on the solidification conditions. As a result, two solidification maps of the Si morphology are proposed, one based on local eutectic solidification conditions and another based on a solidification continuous cooling diagram (SCCT). Both maps help identify the required conditions for certain Si morphologies to form. Hardness measurements were also carried out and it was found that the Si morphology would influence the alloy hardness, with the highest value being achieved when the eutectic Si was globular. This result indicates that the Si morphology is an important factor that can alter the mechanical properties of hypo-eutectic Al-Si alloys.

Evolution of Microstructure in a Low-Si Micro-alloyed Steel Processed Through One-Step Quenching and Partitioning

An attempt has been made in the current study to investigate the possibility of austenite retention in 0.5 wt pct Si steel without Al, processed through the one-step QP however, it was almost independent of partitioning time. The carbon content in the retained austenite did not show any significant variation, after Q&P treatment for different time–temperature combinations. The hardness was found to be sensitive to quench temperature than the partitioning time.

Effects of Cu and Si Contents on the Fluidity, Hot Tearing, and Mechanical Properties of Al-Cu-Si Alloys

The effects of the Cu and Si contents on the fluidity, hot tearing, and mechanical properties of Al-Cu-Si alloys were investigated to evaluate the castability of these widely used forged alloys. Al-Cu-Si alloys with 3.5, 4.5, and 5.5 wt pct Cu and 0, 1.5, and 3.0 wt pct Si were cast at 700 °C in spiral and hot tearing test molds to determine the fluidity and hot tearing characteristics, respectively. With a higher Cu content, the fluidity length decreased by 4.9 and 14 pct, but the hot tearing susceptibility increased from 0.44 to 0.56 and 0.67. With a higher Si content at a fixed Cu content of 4.5 wt pct, the fluidity length increased by 11 pct, and hot tearing was not observed. A solid solution heat treatment was performed at 515 °C for 2 hours and at 525 °C for 8 hours, and the alloy was then quenched in water. Artificial aging was carried out at 185 °C for times of 4, 6, 8, and 10 hours. To improve the fluidity and mechanical properties, 0.10 wt pct Ti was added as a grain refiner. The fluidity increased by 4.6 pct, and the tensile strength increased by 339 MPa.

Effect of Solutes on Grain Refinement of As-Cast Fe-4Si Alloy

Grain size is one of the key microstructural factors that control the mechanical properties of steels. The present work aims to extend the theories of grain refinement which were established for cast light alloys to steel systems. Using a designed Fe-4 wt pct Si alloy (all-ferrite structure during whole solidification process), the solute effect on grain refinement/grain coarsening in ferritic systems was comprehensively investigated. Experimental results showed that boron (B), which is associated with the highest Q value (growth restriction factor) in ferrite, significantly refined the as-cast structure of the Fe-4 wt pct Si alloy. Cu and Mo with low Q values had no effect on grain refinement. However, although Y and Zr have relatively high Q values, addition of these two solutes led to grain coarsening in the Fe-4Si alloy. Understanding the results in regards to the growth restriction factor and the driving force for the solidification led to the conclusion that in addition to the grain growth restriction effect, the changes of thermodynamic driving force for solidification due to the solute addition also played a key role in grain refinement in ferritic alloys.

Two-Zone Microstructures in Al-18Si Alloy Powders

Hypereutectic Al-18 wt pct Si alloy is widely used in automotive industry as a wear-resistant alloy for engine components. However, in the last few years, this traditional composition is being considered for processing by different rapid solidification methods. Positive points include its low thermal expansion and uniform distribution of surface oxides. Nevertheless, the microstructural aspects of Al-Si powders of 18 wt pct Si are still need to be addressed, such as, the eutectic Si morphology, size, and distribution generated by different process conditions during rapid solidification. Based on a detailed quantitative analysis of the microstructures of rapid solidified Al-18 wt pct Si in this work, solidification conditions that yield specific Si morphologies, Si spacing, and thermal cooling conditions are outlined. The focus is determining the solidification conditions that will yield a specified shape of eutectic Si. It is shown that Si morphology is dependent on a combination of growth velocity (based on modified JH model) and temperature gradient. Furthermore, the highest hardness is achieved with globular morphologies of Si. The processing conditions required to achieve these properties are outlined.

Experimental Study on the Activities of Al and Ca in Ferrosilicon

Experiments were carried out to determine the activities of Al and Ca in liquid ferrosilicon (with about 50 wt pct Si) at 1823 K (1550 °C) in their dilution ranges. Liquid FeSi50 and SiO2-Al2O3-CaO slag were stirred mechanically in a graphite crucible to enhance the transfer of Al and Ca between the two phases. The stirring time for the two phases to reach equilibrium was studied. It was found that a time of 45 minutes was long enough to reach the slag–metal equilibrium. The activities of Al and Ca in the ferrosilicon alloy were calculated based on the compositions of the two liquid phases. The activity coefficients obtained for Al and Ca in the liquid FeSi50 at 1823 K (1550 °C) were found to be nearly constant in the composition range studied.

Tracking the Evolution of Annealing Textures from Individual Deformed Grains in a Cross-Rolled Non-oriented Electrical Steel

The evolution of microtexture and microstructure of a cross-rolled 0.88 wt pct Si non-oriented electrical steel was investigated using a quasi-in situ electron backscatter diffraction (EBSD) technique, where individual deformed grains with various initial orientations were tracked during annealing at the same temperature for different times. The textures recrystallized from different deformed grains were compared, and the observations were examined against the preferential nucleation and selective growth theories. Although the cold deformed 〈111〉//ND (normal direction) grains recrystallized first during annealing, they started with significantly different nucleation textures, i.e., γ-fiber (〈111〉//ND) in {111}〈112〉 deformed grains, and cube ({001}〈100〉) in {111}〈110〉 deformed grains. Both recrystallization textures were quite stable until the steel was completely recrystallized. Significant grain growth in these grains was only observed after the recrystallization was complete, which resulted in considerably different final textures as compared to the initial nucleation textures. Deformed grains with a rotated cube ({001}〈111〉) orientation were the last to recrystallize, and the recrystallization was accomplished mainly through the “invading” of neighboring grains into the deformed matrix. Analysis of the misorientations between the rotated cube grain (the matrix) and their neighboring recrystallized grains showed that the preferred growth of some of the grains can be attributed to the high grain boundary mobility associated with the coincident site lattices (CSL). During the course of recrystallization, some $$ \{ 11{\text{h}}\} \left\langle {12\frac{1}{h}} \right\rangle $$ and rotated cube grains also formed, but they disappeared quickly when the annealing time was increased.