The Formation of Martensitic Austenite During Nitridation of Martensitic and Duplex Stainless Steels

Isothermal martensite/ferrite-to-austenite phase transformations have been observed after low-temperature nitridation in the martensite and \(\updelta \)-ferrite phases in 15-5 PH (precipitation hardening), 17-7 PH, and 2205 (duplex) stainless steels. These transformations, in the region with nitrogen concentrations of 8 to 16 at. pct, are consistent with the notion that nitrogen is a strong austenite stabilizer and substitutional diffusion is effectively frozen at the paraequilibrium temperatures of our experiments. Our microstructural and diffraction analyses provide conclusive evidence for the martensitic nature of these phase transformations.     

A Model for Static Recrystallization with Simultaneous Precipitation and Solute Drag

In the present work, we introduce a state parameter-based microstructure evolution model, which incorporates the effect of solute atoms and precipitates on recrystallization kinetics. The model accounts for local precipitate coarsening at grain boundaries, which promotes an average grain boundary movement even if the Zener pinning force exceeds the driving force for recrystallization. The impact of solute drag on the grain boundary mobility as well as simultaneous precipitation is discussed in detail. The model is validated on experimental data on recrystallization in V-micro-alloyed steel, where excellent agreement is achieved.     

Carbide Precipitation in 2.25 Cr-1 Mo Bainitic Steel: Effect of Heating and Isothermal Tempering Conditions

The effect of the tempering heat treatment, including heating prior to the isothermal step, on carbide precipitation has been determined in a 2.25 Cr-1 Mo bainitic steel for thick-walled applications. The carbides were identified using their amount of metallic elements, morphology, nucleation sites, and diffraction patterns. The evolution of carbide phase fraction, morphology, and composition was investigated using transmission electron microscopy, X-ray diffraction, as well as thermodynamic calculations. Upon heating, retained austenite into the as-quenched material decomposes into ferrite and cementite. M₇C₃ carbides then nucleate at the interface between the cementite and the matrix, triggering the dissolution of cementite. M₂C carbides precipitate separately within the bainitic laths during slow heating. M₂₃C₆ carbides precipitate at the interfaces (lath boundaries or prior austenite grain boundaries) and grow by attracting nearby chromium atoms, which results in the dissolution of M₇C₃ and, depending on the temperature, coarsening, or dissolution of M₂C carbides, respectively.     

Calculation of cosmic ray limited maximum DC blocking voltages of high voltage silicon PIN diodes

A power law approach as used by Fulop for the treatment of impact ionization and breakdown in abrupt silicon P–N junctions [Fulop W. Calculation of avalanche breakdown voltages of silicon P–N junctions. Solid-State Electron. 1967;10:39–43] is developed in this paper to provide simple-to-use equations for the quantitative evaluation of cosmic ray related phenomena in high voltage power devices. Being empirical in nature, such approaches have no physical background and only serve the purpose of generating a simple and compact mathematical framework. The resulting compact model allows for a quick and straightforward computation of DC blocking voltages as a function of FIT rate, n-base doping and temperature. The determination of model parameters is based on the theory and data given in [Zeller HR. Cosmic ray induced failures in high power semiconductor devices. Solid-State Electron. 1995;38(12):2041–6]. With the new approach, calculating first-hand maximum DC blocking voltages for high voltage power semiconductor devices becomes as effortless as the calculation of the breakdown voltage.     

Water Reuse Fit for Purpose by a Sustainable Industrial Wastewater Management Concept

Water shortage is often a challenge for industrial park developments. To ensure a more sustainable water supply, the Industrial Wastewater Management Concept with a focus on Reuse (IW²MC→R) provides a strategy to meet the challenges. Main requirements to achieve water reuse fit for purpose are optimized wastewater treatment, an optimized sewer and pipe system, and an innovative water quality monitoring concept. To evaluate water‐reuse concepts, a reuse factor is calculated, which relates to all wastewater inflows to the central wastewater treatment plant and all reuse‐water flows.     

A novel approach to model the land mobile satellite channel through reversible jump markov chain monte carlo technique

A key issue in the design of a mobile satellite communication system is an adequate knowledge of the statistical behavior of the propagation channel. To achieve this goal, the development of very accurate models plays a very important role. In contrast to traditional multi-state Markov chain based models, the novel approach proposed in this paper makes no prior assumptions on the number of states or on the statistical distributions characterizing each state. The sequence of channel states is blindly estimated using a Reversible Jump Monte Carlo Markov Chain algorithm.     

Biosynthesis of Jasmonates from Linoleic Acid by the Fungus Fusarium oxysporum. Evidence for a Novel Allene Oxide Cyclase

Fusarium oxysporum f. sp. tulipae (FOT) secretes (+)-7-iso-jasmonoyl-(S)-isoleucine ((+)-JA-Ile) to the growth medium together with about 10 times less 9,10-dihydro-(+)-7-iso-JA-Ile. Plants and fungi form (+)-JA-Ile from 18:3n-3 via 12-oxophytodienoic acid (12-OPDA), which is formed sequentially by 13S-lipoxygenase, allene oxide synthase (AOS), and allene oxide cyclase (AOC). Plant AOC does not accept linoleic acid (18:2n-6)-derived allene oxides and dihydrojasmonates are not commonly found in plants. This raises the question whether 18:2n-6 serves as the precursor of 9,10-dihydro-JA-Ile in Fusarium, or whether the latter arises by a putative reductase activity operating on the n-3 double bond of (+)-JA-Ile or one of its precursors. Incubation of pentadeuterated (d₅) 18:3n-3 with mycelia led to the formation of d₅-(+)-JA-Ile whereas d₅-9,10-dihydro-JA-Ile was not detectable. In contrast, d₅-9,10-dihydro-(+)-JA-Ile was produced following incubation of [17,17,18,18,18-²H₅]linoleic acid (d₅-18:2n-6). Furthermore, 9(S),13(S)-12-oxophytoenoic acid, the 15,16-dihydro analog of 12-OPDA, was formed upon incubation of unlabeled or d₅-18:2n-6. Appearance of the α-ketol, 12-oxo-13-hydroxy-9-octadecenoic acid following incubation of unlabeled or [¹³C₁₈]-labeled 13(S)-hydroperoxy-9(Z),11(E)-octadecadienoic acid confirmed the involvement of AOS and the biosynthesis of the allene oxide 12,13(S)-epoxy-9,11-octadecadienoic acid. The lack of conversion of this allene oxide by AOC in higher plants necessitates the conclusion that the fungal AOC is distinct from the corresponding plant enzyme.     

Pyrotechnic Countermeasures: IV. Radiometric Performance of a Sulphur‐based Flare Composition

Radiometric performance of a sulphur‐based flare composition has been investigated. Composition comprising sulphur, potassium perchlorate and antimony sulphide has acceptable band ratio but an order of magnitude weaker spectral efficiency than typical carbon‐based compositions. The use of other sulphur compounds with potential for increased performance is discussed. For part III see Ref. [1].     

Bewertung der Alkalireaktivität von Gesteinskörnungen

Assessment of the Alkali‐Reactivity of Aggregates Damages to concrete structures caused by the involvement of alkali‐silica reaction (ASR) are still today a world‐wide problem and increased in the last years despite of intensive research, available standards and guidelines. Especially pavement concretes (roads, airports) are affected by ASR due to the external alkali‐supply by deicers. At the F.A. Finger‐Institute for Building Material Sciences (FIB), a combination of an accelerated mortarbar test and comprehensive petrographic and mineralogic examinations are used for a short‐term assessment of the alkali‐reactivity of aggregates. For a reliable assessment of the ASR damage‐potential of specific concretes, a new developed ASR performance‐test, the cyclic climate storage, is used.     

Reverted austenite in PH 13-8 Mo maraging steels

The mechanical properties of maraging steels are strongly influenced by the presence of reverted austenite. In this study, the morphology and chemical composition of reverted austenite in a corrosion resistant maraging steel was characterized using transmission electron microscopy (TEM) and atom probe tomography (APT). Two types of austenite, i.e. granular and elongated, are present after aging at 575 °C, whereby the content of the latter increases during aging. The investigations revealed that the austenite phase is enriched in Ni, which prevents the transformation to martensite during cooling. Inside and next to the austenitc areas, Mo and Cr-rich carbides, which form during the aging treatment, were found. Various aging treatments were performed to obtain the activation energy for the formation of reverted austenite. Additionally, the experimental data are compared with thermodynamic and kinetic simulations. Based on these results and the chemical composition changes of the phases, a model for the formation of reverted austenite is presented. It is concluded that precipitation of B2-ordered NiAl and formation of reverted austenite take place simultaneously during aging and that dissolution of precipitates is not essential for the initial formation of reverted austenite.