Microstructural control and properties optimization of microalloyed pipeline steel

A series of physical simulations, with parameters resembling those of industrial rolling, were applied using a thermo-mechanical simulator on microalloyed bainitic pipeline steel to study the influence of varying the processing parameters on its microstructure evolution and mechanical properties. In this study, the austenitization temperature and roughing parameters were kept unchanged, whereas the parameters of the finishing stage were varied. The developed microstructures were studied using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). It is illustrated that selecting the appropriate cooling strategy (without altering the deformation schedule) can produce an optimized microstructure that breaks through the strength–ductility trade-off. Increasing the cooling rate after the finishing stage from 10 K·s−1 to 20 K·s−1 activated the microstructure refinement by effective nucleation of acicular ferrite and formation of finer and more dispersed martensite/austenite phase. This resulted in a remarkable enhancement in the ductility without compensating the strength. Furthermore, a pronounced strength increase with a slight ductility decrease was observed when selecting the appropriate coiling temperature, which is attributed to the copious precipitation associated with locating the coiling temperature near the peak temperature of precipitation. On the other hand, it was observed that the coiling temperature is the predominant parameter affecting the strain aging potential of the studied steel. Higher strain aging potentials were perceived in the samples with lower yield strength and vice versa, so that the differences in yield strength after thermo-mechanical treatments evened out after strain aging

Nano-bainitic steels: acceleration of transformation by high aluminum addition and its effect on their mechanical properties

Additions of 3 and 5 wt.% Al have been investigated as a low-cost method for transformation acceleration in nano-bainitic steels. For both Al contents, two groups of steels with C-content in the range ~0.7 to ~0.95 wt.% were studied. Thermodynamic and physical simulations were used in alloy and heat treatment design. Characterization was performed via dilatometry, scanning and transmission electron microscopy, Synchrotron X-ray diffraction, and tensile and impact testing. Fast bainitic-transformation time-intervals ranging from 750–4600 s were recorded and tensile strengths up to 2000 MPa at a ductility of ~10 elongation percent were attainable for the 3 wt.% Al group at an austempering temperature of 265 ◦C. Higher Al additions were found to perform better than their lower Al counterparts as the austempering temperature is dropped. However, Al lowered the austenite stability, increased the martensite start temperature, austenitization temperatures and, consequently, the prior austenite grain size, as well as limiting the austempering temperatures to higher ones. Additionally, the lowered austenite stability coupled with higher additions of hardenability elements (here carbon) to maintain the martensite start at around 300 ◦C, causing the 5 wt.% Al group to have a large amount of low stability retained austenite (and consequently brittle martensite) in their microstructure, leading to a low elongation of around 5%

Strain hardening dependence on the structure in dual-phase steels

Herein, an extensive study is presented on the microstructure–tensile properties relationship in dual-phase (DP) steels. A series of ferrite-martensite DP steels with varied martensite volume fractions ( V m) from 0.17 to 0.86, microstructure morphologies (globular and elongated) and structure finenesses (ferrite grain sizes from 1.9 to 10.7 μm) are produced applying appropriate heat treatments. The tensile properties are studied, and the strain hardening behavior is analyzed in terms of Holloman, Crussard–Jaoul (C–J) and modified C–J approaches. The tensile curves reveal up to three strain hardening stages with the highest strain hardening exponent at the beginning of straining. Increasing V m and refining the structure raises the number of strain hardening stages and improves the strain hardening capacity in the first stage (n1). For the DP steels with similar morphologies, the mean free path in ferrite (λf) is proposed to be the most significant microstructure factor affecting n 1 -value. The n 1 of the elongated morphology shows stronger dependence on λf than the globular one. Finally, the DP steels are subjected to aging treatments, which lead to improved yield strength and total elongation, however, the strain hardening exponent decreases significantly

Audit Committee Effectiveness, Audit Quality and Earnings Management: An Empirical Study of the Listed Companies in Egypt

The role of audit committees and audit quality in ensuring the quality of corporate financial reporting has come under considerable scrutiny due to recent high-profile earnings management cases in the world. The purpose of this paper is to examine the association between the audit committee effectiveness, audit quality and earnings management practices of more active 50 Egyptian companies listed on the Egyptian Stock Exchange of the non-financial sector during the period 2007-2010. After controlling for size, leverage and cash flow from operation activities, the results of univariate and multivariate analyses indicated that audit committees independence; experience of audit committee members; audit committee meetings; and audit quality have significant negative association with discretionary accruals as a proxy for earnings management. On the other hand, no significant relationship is found between audit committees size and the level of discretionary accruals. This paper is important because it offers useful information that is of great value to policy makers, academics and other stakeholders. Keywords: Audit Committee Effectiveness, Audit Quality, Earning Management, Egyp

Effect of thermo-mechanical processing on structure and properties of dual-phase matrix ADI with different Si-contents

The improvement in the combination between strength and ductility of austempered ductile iron with dual matrix structure was investigated in two ductile irons having different silicon contents, namely 2.6 wt% and 4.0 wt%. The structure was produced in a thermo-mechanical simulator, equipped with a dilatometry system. The effect of silicon content on the transformation kinetics and mechanical properties was studied. For both ductile irons, the influence of introducing ferrite into the matrix on the structure development and mechanical properties was investigated and compared to those of completely ausferritic matrix. Increasing the Si-content widened the intercritical region and shifted it to higher temperature range. The former effect renders the intercritical annealing process more controllable. The introduction of the ferrite phase accelerated the ausferrite transformation kinetics and improved both the ductility and the formability index (ductility × ultimate strength), while both yield and ultimate strength declined

Nanobainite generated in low- and medium-carbon steels via an economical alloying strategy

A low-cost strategy for generating fast transforming nanobainitic (nB) steels in low- and medium-carbon alloys is investigated. Accelerating the bainite transformation relies on adding 0.7–3 wt% Al. Alloys and heat treatments are designed via thermodynamic calculations and dilatometry. nB microstructures are generated via isothermal holding and continuous cooling. The microstructures generated are investigated via microscopy and mechanical characterization. Incubation periods less than 150 s as well as isothermal transformation times ranging from 2000 to 4000 s are recorded for all conditions. Increasing the Al content from 0.7 to 2.8 wt% lowers the incubation and transformation times from 150 to 15 s and 3000 to 2000 s, respectively, at a cost of a reduction in tensile strength and elongation % (EL%) from 1330 to 1270 MPa and from 13.5 to 7.7%, respectively. The introduction of δ-ferrite to the microstructure of the high Al alloy increased EL% up to 16% and reduced the tensile strength to 1105 MPa. Continuous cooling at a rate of 0.03 K s-1 increased the tensile strength by 100 MPa at similar EL%. Lowering the cooling rate to 0.003 K s-1 yielded similarproperties as isothermal treatment because most of the transformation is concluded near the starting temperature

An efficient technique for out-of-band power reduction for the eliminated CP-STC-shaped system for 5G requirements

The most dominant needs for the recent wireless mobile applications are higher bandwidth (BW) efficiency, higher energy efficiency higher quality of services (QOS). The main technique in 4G systems is OFDM but it suffers from some limitations such as large peak to average power ratio (PAPR), higher Out-of-Band (OOB) power radiation, and wasting bandwidth efficiency due to cyclic prefix (CP) extension. In his paper, these OFDM limitations will be reduced with low computational complexity compared to filter bank multicarriers (FBMC). The proposed scheme is based on symbol time compression (STC) for OFDM system. The proposed STC-Shaped system is achieved via interleaver-spreader and symbol shaper in the transmitter side in addition to equalization and combining processes in the receiver side. Comparative study between the proposed system and the conventional OFDM in case of additive white Gaussian noise (AWGN) and COST 207 typical multipath fading channel will be presented. The numerical results show that the proposed STC-Shaped scheme reduces OOB significantly. The proposed scheme improves BER in multipath Rayleigh fading although it is without CP. Thus, the proposed system is more robust against inter symbol interference (ISI) compared to conventional OFDM system. Also, the numerical results show that the PAPR of the proposed system is decreased significantly and also, it is derived theoretically. Also, the proposed scheme overcomes CP extension, and hence increases the bandwidth (BW) efficiency. Finally, the computational complexity for the proposed scheme is derived and it has very low complexity compared to FBMC. The system performance measurments has been fulfilled using cumulative distribution function (CDF), power spectral density (PSD) and bit error rate (BER)

Developing an Efficient Secure Query Processing Algorithm on Encrypted Databases using Data Compression

Distributed computing includes putting aside the data utilizing outsider storage and being able to get to this information from a place at any time. Due to the advancement of distributed computing and databases, high critical data are put in databases. However, the information is saved in outsourced services like Database as a Service (DaaS), security issues are raised from both server and client-side. Also, query processing on the database by different clients through the time-consuming methods and shared resources environment may cause inefficient data processing and retrieval. Secure and efficient data regaining can be obtained with the help of an efficient data processing algorithm among different clients. This method proposes a well-organized through an Efficient Secure Query Processing Algorithm (ESQPA) for query processing efficiently by utilizing the concepts of data compression before sending the encrypted results from the server to clients. We have addressed security issues through securing the data at the server-side by an encrypted database using CryptDB. Encryption techniques have recently been proposed to present clients with confidentiality in terms of cloud storage. This method allows the queries to be processed using encrypted data without decryption. To analyze the performance of ESQPA, it is compared with the current query processing algorithm in CryptDB. Results have proven the efficiency of storage space is less and it saves up to 63% of its space.