Grain-oriented Fe-3%Sisteel is a soft magnetic material that is widely used as a core material of pole and power transformers. The low core loss can be achieved by the highly textured microstructure with Goss orientation, f110gh001i because h001i direction in iron is the easiest magnetization direction with low magnetic losses. 1) Such a strong Goss texture could be obtained after secondary recrystallization which is also referred to as abnormal grain growth (AGG). However, the mechanism of selective Goss AGG has not yet been clearly understood since its ﬁrst report by Goss in 1935. 2)
However, due to high Si in such steel (2.7% Si), hot workability is adversely affected. This is reflected in form of elongated structure with high dislocation density. Presence of second phase (austenite), if any, also leads to differential flow leading to cracking thus showing poor workability. In view of this, efforts were made to study such behavior occurring during its processing stages by performing uni-axial compression tests on 2.7% Sisteel.
The effect of electric current pulse (ECP) treatment on grain orientation in a cold-rolled Fe 3 % Sisteel was investigated in this study. Results showed that the recrystallized nuclei preferred to form along the current direction in the primary period of recrystallization. The theoretical analysis revealed that the anisotropic nucleation orientation was ascribed to the different dislocation mobility derived from the electron wind force during the passing of electric current. Hence, the ECP treatment should be a special and effective method to control the nucleation orientation, and the present work is of great technological and physical importance. [doi:10.2320 / matertrans.M2011272]
The steel investigated was a hot rolled steel of composition 0.2C-3.51Mn-1.52Si-0.25Mo-0.04Al (wt pct). Manganese enhances the austenite stability and thus retards the formation of ferrite, pearlite, and bainite, which results in a shift of the TTT- and CCT-curves of these phases to longer times. The combination of low-carbon and high-silicon contents minimizes and delays the carbide precipitation during the isothermal holding. The as-received material was hot rolled into a 4mm-thick steel slab. Dilatometry speci- mens were taken from hot rolled slabs, parallel to the rolling direction. These were cylindrical of dimensions 10 mm in length and 3.5 mm in diameter. All specimens were heat-treated using a Ba¨hr 805A dilatometer. The specimens were placed between two quartz rods, heated by an induction coil, and cooled using nitrogen gas. A thermocouple was spot-welded in the middle of the specimens to measure and control the temperature.
Therefore as compared with MIG sample, MAG sample has low corrosion near the weld metal. This is probably be- cause the amount of heat input is lower in MAG sample on account of higher welding speed. Then, the concentrations of Al and Si are almost the same between α and γ phase near the weld metal. Therefore, there is no special corrosion near the weld metal. It is found that only at the beginning of the corrosion, Al-Sisteel has the sensitivity near the weld metal in the case of high amount of heat in welding. After the ini- tial time of the test, welded Al-Sisteel exhibits high corro- sion resistance because of the formation of the protective rust containing Al and Si in inner rust.
Considering these background facts, the factor that is more dominant in inducing AGG needs to be identiﬁed between mobility and energy advantages. Comparisons of the mobi- lity and the energy advantages in grain growth have been carried out previously by Rollet et al. 17) and Hwang et al. 8) By two-dimensional (2-D) MC simulations, Rollet et al. 17) have shown that AGG can occur if a potential grain for AGG is surrounded by 100% of either high-mobility or low-energy grain boundaries. These conditions would be satisﬁed by polycrystalline materials with an ideal texture. In a real sample such as Fe-3%Sisteel, however, the misorientation distribution of abnormally growing Goss grain boundaries is not much diﬀerent from that of the other grain boundaries. 6)
To overcome the limited applicability of the conventional DLTS for near-surface defects, we present in this paper a detailed analysis of the dislocation-related defect levels for strained-Si top layers using minority carrier transient spectroscopy (MCTS) method. Unlike DLTS which fills deep levels using electrical pulses, MCTS injects minority carriers by directing a light pulse of above-band-gap energy on a semitransparent Schottky diode to excite both majority and minority carriers. The majority carrier generated in the neutral material is prevented from entering the depletion region by the electric field, whereas minority carriers generated in the neutral material within a diffusion length are extracted by the depletion field, resulting in a higher concentration of minority carriers within the depletion region. Thus, MCTS can effectively fill and empty the defect levels located within the W-λ layer, enabling the detection of deep levels located within strained-Si layer, and/or constant SiGe layer.
The precipitates in the quenched and tempered Base, Base-Mo-V, and Base-Cr-Mo-V-Si specimens were characterised using a JEOL 7000 scanning electron microscope (SEM) operating at 20 kV with a field emission gun (FEG). Generally, the magnification for the SEM images was X12000 to observe the development of precipitation for all conditions. However, in terms of characterising the precipitate size, volume fraction, number density and particle separation during tempering, the magnification of the SEM images was chosen differently in order to obtain a similar number of precipitates in each condition. At least five SEM images (including approximately 1000 particles) were selected, and Axiovision 4.6.3 image analysis software was used to obtain the particle sizes (length, width, and radius based on the equivalent circle diameter (ECD) method), distribution, number densities, volume fractions and separations between particles for tempered samples. Here, the number density and volume fraction measurements were based on the assumption that all the precipitates in the SEM images were from the surface of the specimens.
and 461.0 eV 兲 . After oxidation a large shift is observed for both features, which is attributed to the chemical shift from the oxide formation, giving values consistent with reported values 共 458.5– 459.0 eV 兲 . 13,14 As the Ti oxide thickness in- creases, small shifts are observed, which again follow the shifts of the bulk Si 2 p peak. Compared with the changes in the Si 2 p peak and the O 1s peak, the results in Fig. 3 dem- onstrate that the Ti 2 p core levels do not show significant shifts in binding energy between Ti silicate and TiO 2 phases. However, the widths of the doublet features for 0.4 nm films and 0.8 nm, in which the Ti silicate fraction is relative large, are broader than those for the TiO 2 film of thickness 3.2 nm. This suggests that there is insufficient resolution to separate the 0.4 and 0.8 nm features into Ti silicate and TiO 2 compo-
The Ni-Cr-Si-B group was the first Chromium containing brazing alloy system entering into industrial applications . Out of this group, BNi-2 filler metal is the ideal choice for protective atmosphere furnace brazing for a wide variety of brazed parts. This brazing alloy became the most widely employed Nickel filler metal because of three factors: (i) compatibility with almost every base material, (ii) availability in powder, paste, tape and amorphous foil form, (iii) low cost . The brazing temperature of Ni-Cr-B-Si filler metals is strongly
Si-Mn alloyed spring steels suitable for elastic rail clip (ERC) need to have high fatigue resistance in addition to high modulus of elasticity and resilience defined as energy absorbed during elastic deformation depicted by area under stress – strain plot upto elastic limit. In view of the properties required in spring steel, it is necessary to engineer a tempered-martensitic microstructure typified by high hardness (> 360 BHN) . Further, it is critical to ensure absence of any surface / sub-surface cracks or matrix inclusion interface larger than a critical size where fatigue failure originate. In view of above, stringent requirement for inclusion rating in the final product assumes significance in addition to defect free macrostructure of cast billets. Usually top poured (TP) ingots have limitation in restricting the defect free surface in form of rolled scabs which is unacceptable for ERC.
Figures 2(a) and (b) show the surface structure of the carbon steels subjected to bombardment for 40 s with the glassy alloy shots and the cast alloy shots, respectively. It is seen that the steel sheet bombarded with the glassy alloy shots has a much homogeneous crater-like surface pattern as compared with that for the cast steel shots. In addition, the average size of the crater-like pattern was measured as about 20 mm for the glassy alloy shots and about 7 mm for the cast steel shots. The distinct diﬀerence in the crater-like pattern indicates that the bombarded area generated by one bom- bardment is much larger for the glassy alloy shots. The average height of the crater edges was measured as 15 mm for the glassy alloy shots and 5 mm for the cast steel shots, being much larger for the former shots. The larger height is thought to result from the larger bombarded area. The signiﬁcant diﬀerence in the surface structure seems to result from the much smaller Young’s modulus and higher strength for the glassy alloy, as discussed later in section 4. Figures 3(a) and (b) show the cross sectional structure of the steel sheets subjected to bombardment for 40 s with the glassy alloy shots and the high speed steel shots, respectively. The etched microstructure enables us to distinguish clearly the shot- peening eﬀected region and the non-eﬀected region. The depth of the eﬀected region from the sheet surface is measured to be about 100 mm for the glassy alloy shots and about 45 mm for the cast steel shots. It is thus noticed that the use of the glassy alloy shots can produce a much thicker eﬀected region in spite of the same shot peening condition. The X-ray diﬀraction patterns of the shot regions in the steel sheets subjected to bombardment for 40 s with the glassy alloy and cast steel shots are shown in Fig. 4, together with the data of the enlarged (111) -Fe diﬀraction peaks and the
Abstract: Slag is co-product of the iron and steel making process. The use of steel slag reduces the need of natural rock as constructional material, hence preserving our natural rock resources, maximum utilization and recycling of by-products and recovered waste materials for economic and environmental reasons has led to rapid development of slag utilization. The use of steel aggregate in concrete by replacing natural aggregates is a most promising concept.
where D is the diffusivity of Si through the liquid droplet, X is the Si atomic fraction in the liquid, dX/dT is the atomic fraction change with respect to temperature 共 inverse liquidus slope 兲 , and “ T is the temperature gradient of the substrate. The variables X, dX/dT, and D are temperature dependent. To investigate the dominant factor affecting the increased velocity of Pt-Si droplets with increasing temperature, we adopted the above velocity equation and estimated the varia- tion for each factor. Although the velocity equation was de- duced for the migration of a three-dimensional droplet in a three-dimensional 共 3D 兲 solid, the expression is not depen- dent on shape. This expression should describe the surface migration of the Pt-Si liquid droplets, since the droplets pen- etrate into the substrate and have significant 3D character and the temperature gradient is predominantly along the sur- face. In our analysis the variables X and dX/dT were ob- tained from the liquidus curve of the Pt-Si binary phase dia- gram, and D was calculated from the above velocity equation. The results are summarized in Table II. The domi- nant factor is (dX/dT) “ T, which is attributed to the concen- tration gradient in the liquid droplet. As the temperature in- creases, the dissolution of Si near the hot interface increases significantly, and the concentration gradient in the droplet would be likewise increased, which would enhance the Si transport rate. Thus, within this model the increase in droplet velocity with increasing temperature would be due to the enhancement of dissolution at the hot interface.
The proposed theme for this research is to study the performance of cutting tools. The development of the work was performed based on a specific process of metal machining: milling, which can be defined as a process of thinning and finishing of materials in order to obtain parts and devices with diverse and complex geometries. For this, in addition to being a process with the option of subprocesses adjacent to the milling itself, thinning and finishing can be performed with different cutting tools. The concordant peripheral milling is the process that was analyzed in the development of the planned experiments, for the analysis of breakdowns, wear and life of the high yield thinning inserts and finishing, used in the machining of the MnSi alloy surface in substrate steel SAE 1020.
standard wafers cleaning process, a 5-nm thick Zr film was sputtered on the cleaned Si substrates by an RF sputtering system. Following that, samples were loaded into a horizontal tube furnace and were heated up from room temperature to 700°C in an Ar flow ambi- ent, and the heating rate was fixed at 10°C/min. Once the set temperature was achieved, N 2 O gas was intro-
By increasing the hardness, the resistance of the surface layers against normal load increases resulting in lower coefficient of friction. Friction variations resulting from sliding were characterized by randomly fluctuating behavior for untreated and plasma nitrided samples (Figure 8). This variation in friction behavior has been observed by many investigators. The friction variation of the PECVD sample was very low. The friction behavior was very smooth until approximately 300 m sliding distance and gradually increased with increasing distance. The low friction value until 300 m is also related to the intrinsic low friction nature of silicon nitride (α- Si 3 N 4 ) compound .
Figure 4shows the erosion rate for different runs for the uncoated CA6NM steel. The erosion rate is maximum for run 3 and minimum for the run 1.The angle in run 3 is 90°, concentration and velocity is maximum while particle size is minimum. The erosion rate is similar for run 7 and 2, in these both similar concentrations is used, while angle is 60° and30° respectively. After one hour the difference in erosion rate is more significant for different runs.
1970 s, the demand for a soft magnetic material with exceptional electrical resistivity for high-frequency audio equipment brought 6.5 wt% silicon steel back into the limelight. Its inherently higher electrical resistivity and near-zero magnetostriction made it a perfect material for applications at high frequencies as it could minimize losses from both eddy current loss and shape changes . This sparked a renewed effort to find alternative ways to process the brittle material, and many methods were tested over the next few years in- cluding melt spinning, chemical vapor deposition (CVD), twin rolling, and powder metallurgy [45–48]. Melt spinning showed great promise in producing a low-cost 6.5 wt% silicon steel [49–51]. As demon- strated by Liang et al. , 30-mm-wide continuous tapes could be successfully produced by melt spinning, and their excellent ductility ensured that the tapes could be coiled into spools. However, the in- dustry did not switch over immediately to 6.5 wt% silicon steel due to the increased cost, and it is only with the recent demand for even more efficient electric motors and high-voltage transformers that the high silicon steel is finally on the verge of being accepted as a commercially viable soft magnetic material .