Determination of the structure-processing-properties relationship of Fe-6.5wt%Si

The role of Fe-6.5wt%Si as a soft magnetic material in motor and power generation will continue to increase as power and efficiency demands keep increasing due to high silicon steel’s superior magnetic and electrical properties when operated at high frequencies. However, the presence of brittle phases creates challenges for mass production of the materials and for machining the materials into parts with demanding geometries. Understanding the processing parameters controlling the presence of the brittle phases is necessary to promote high silicon steels as the superior soft magnetic material. This research pioneers the use of in-situ cooling rate thermal imaging analysis and a 2D Laue x-ray detector to quantify the relationship among processing parameters, final microstructure of melt-spun ribbons and the associated physical properties. These techniques reveal the superlattice peaks of the ordered B2/D03 phases separating them from the background A2 phase. Utilizing a variety of techniques investigating mechanical, electrical, and magnetic properties’ correlation to crystal structure alongside processing parameters a time temperature transformation curve can be generated

Validation of Toolmark Comparisons Made At Different Vertical and Horizontal Angles

Numerous studies have focused on determining whether objective statistical methods can be used to discriminate between known matches and nonmatches when comparing laboratory prepared toolmarks. This study involved an analysis of striated toolmarks made as a function of varying vertical and horizontal angles of attack. Comparisons based on experimental data show that replicate toolmarks from the same tool show high correlation values at identical vertical and horizontal angles, with the correlation decreasing as the angular difference increases, especially for horizontal angular changes. Comparisons between nonmatching samples produce low correlation values that remain unchanged as horizontal angular differences increase. While complete statistical separation was not achieved between matching and nonmatching samples, there is evidence demonstrating that toolmarks can be identified if the variation in horizontal angle is within 10°. The experiment shows that computer‐aided comparison techniques could be viable for identification with the proper statistical algorithm

Review of Fe-6.5 wt%Si high silicon steel—A promising soft magnetic material for sub-kHz application

To meet the growing need for energy efficiency in power electronics and electric machines, a number of new soft magnetic materials are being investigated. Among them, high silicon Fe-Si alloy has been recognized as a promising candidate for low-to-medium-frequency applications. Compared to the currently most widely used 3 wt% silicon steel, the steel containing 6.5 wt% Si possesses more favorable properties, including high electrical resistivity, good saturation magnetization, and near-zero magnetostriction. However, the high silicon content facilitates the formation of ordered phases, resulting in severe brittleness that prohibits mass production using the economical conventional processing methods. A number of new processing routes have been investigated and inspiring progress has been made. Prototypes of motors and transformers using high silicon steel have been demonstrated with improved efficiency and power density. If the processing cost and limitations of size and shape are properly addressed, high silicon steel is expected to be widely adopted by the industries. Among all the investigated processing techniques, rapid solidification appears to be the most cost-effective method for mass producing thin sheet of high silicon steel. This paper reviews the current state-of-the-art of the Fe-Si based soft magnetic materials including their history, structure, properties, processing, and applications

Development of a Mobile Toolmark Characterization/Comparison System

Since the development of the striagraph, various attempts have been made to enhance forensic investigation through the use of measuring and imaging equipment. This study describes the development of a prototype system employing an easy‐to‐use software interface designed to provide forensic examiners with the ability to measure topography of a toolmarked surface and then conduct various comparisons using a statistical algorithm. Acquisition of the data is carried out using a portable 3D optical profilometer, and comparison of the resulting data files is made using software named “MANTIS” (Mark and Tool Inspection Suite). The system has been tested on laboratory‐produced markings that include fully striated marks (e.g., screwdriver markings), quasistriated markings produced by shear‐cut pliers, impression marks left by chisels, rifling marks on bullets, and cut marks produced by knives. Using the system, an examiner has the potential to (i) visually compare two toolmarked surfaces in a manner similar to a comparison microscope and (ii) use the quantitative information embedded within the acquired data to obtain an objective statistical comparison of the data files. This study shows that, based on the results from laboratory samples, the system has great potential for aiding examiners in conducting comparisons of toolmarks

Characterization of ordering in Fe-6.5%Si alloy using X-ray, TEM, and magnetic TGA methods

Fe-6.5wt%Si steel surpasses the current extensively used Fe-3.2wt%Si steel in lower iron loss, higher permeability, and near zero magnetostriction. As a cost effective soft magnetic material, Fe-6.5wt%Si may find applications in motors, transformers, and electronic components. However, the brittleness of the alloy poses processing challenges. The brittleness in Fe-6.5wt%Si is attributed to the formation of ordered phases. Evaluation of the amount of ordered phases is important for the research and development of Fe-6.5wt%Si. This paper aims to find effective ways to evaluate the ordering degree through a comparison of various characterization techniques. In order to tune the ordering degree, various speeds were used to prepare Fe-6.5wt%Si samples via melt spinning. The varying wheel speed changes the cooling rate, which was confirmed by thermal imaging. In addition to the widely used TEM and normal theta-2theta X-ray diffraction methods, two quantitative methods were adopted for this Fe-6.5wt%Si system to study the ordering degree. One method is based on rotating crystal XRD technique, and the other is magnetic thermal analysis technique. These two methods effectively quantified the varying degree of ordering presented in the samples and were deemed more suitable than the TEM, normal theta-2theta XRD methods for Fe-Si due to their ease of sample preparation and short turn-around time

Thermodynamic and kinetic analysis of the melt spinning process of Fe-6.5 wt.% Si alloy

The microstructural evolution of Fe-6.5 wt.% Si alloy during rapid solidification was studied over a quenching rate of 4 × 104 K/s to 8 × 105 K/s. The solidification and solid-state diffusional transformation processes during rapid cooling were analyzed via thermodynamic and kinetic calculations. The Allen-Cahn theory was adapted to model the experimentally measured bcc_B2 antiphase domain sizes under different cooling rates. The model was calibrated based on the experimentally determined bcc_B2 antiphase domain sizes for different wheel speeds and the resulting cooling rates. Good correspondence of the theoretical and experimental data was obtained over the entire experimental range of cooling rates. Along with the asymptotic domain size value at the infinite cooling rates, the developed model represents a reliable extrapolation for the cooling rate \u3e 106 K/s and allows one to optimize the quenching process

Determination of the structure-processing-properties relationship of Fe-6.5wt%Si

The role of Fe-6.5wt%Si as a soft magnetic material in motor and power generation will continue to increase as power and efficiency demands keep increasing due to high silicon steel’s superior magnetic and electrical properties when operated at high frequencies. However, the presence of brittle phases creates challenges for mass production of the materials and for machining the materials into parts with demanding geometries. Understanding the processing parameters controlling the presence of the brittle phases is necessary to promote high silicon steels as the superior soft magnetic material. This research pioneers the use of in-situ cooling rate thermal imaging analysis and a 2D Laue x-ray detector to quantify the relationship among processing parameters, final microstructure of melt-spun ribbons and the associated physical properties. These techniques reveal the superlattice peaks of the ordered B2/D03 phases separating them from the background A2 phase. Utilizing a variety of techniques investigating mechanical, electrical, and magnetic properties’ correlation to crystal structure alongside processing parameters a time temperature transformation curve can be generated.</p

Validation of Toolmark Comparisons Made At Different Vertical and Horizontal Angles

Numerous studies have focused on determining whether objective statistical methods can be used to discriminate between known matches and nonmatches when comparing laboratory prepared toolmarks. This study involved an analysis of striated toolmarks made as a function of varying vertical and horizontal angles of attack. Comparisons based on experimental data show that replicate toolmarks from the same tool show high correlation values at identical vertical and horizontal angles, with the correlation decreasing as the angular difference increases, especially for horizontal angular changes. Comparisons between nonmatching samples produce low correlation values that remain unchanged as horizontal angular differences increase. While complete statistical separation was not achieved between matching and nonmatching samples, there is evidence demonstrating that toolmarks can be identified if the variation in horizontal angle is within 10°. The experiment shows that computer‐aided comparison techniques could be viable for identification with the proper statistical algorithm.This is the peer-reviewed version of the following article: Macziewski, Chad, Ryan Spotts, and Scott Chumbley. "Validation of Toolmark comparisons made at different vertical and horizontal angles." Journal of Forensic Sciences 62, no. 3 (2017): 612-618., which has been published in final form at DOI: 10.1111/1556-4029.13342. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving. Posted with permission.</p