Microstructural development in cast alloys based on the β-NiAl–β′-Ni2AlTi–γ′-Ni3Al–α-Cr system

An investigation of microstructural development in three arc-cast Ni–Al–Cr–Ti multiphase alloys derived from the B2 type -NiAl phase is presented. Detailed microstructural characterization of Ni–25 at % Al–20 at % Cr–15 at % Ti, Ni–26 at % Al–21 at % Cr–11 at % Ti and Ni–25 at % Al–24 at % Cr–15 at % Ti materials by transmission electron microscopy (TEM), is described. Microstructural development is examined in both the as-cast condition and after 140 h homogenization treatments at both 850 and 1100 °C. The formation of a eutectic between an L21-type phase (Heusler phase, with a nominal composition of Ni2AlTi) and elemental -Cr is examined. The precipitation of within () and vice versa, in both the inter- and intradendritic regions, is considered. The formation of L12-type (nominally Ni3Al) precipitates within the and -phases is discussed, as is the transformation of to two-phase / during ageing. © 1998 Chapman & Hall     

Bulk-alloy microstructural analogues for transient liquid-phase bonds in the NiAl/Cu/Ni system

Transient liquid-phase (TLP) bonds between dissimilar materials can have complex microstructures that evolve both during holding at the bonding temperature and on cooling. In this article, an examination is made of the feasibility of producing bulk-alloy microstructural analogues for individual microstructural features of dissimilar material TLP bonds. The ultimate intent of this work is to enable the contribution of individual microstructural features to the overall properties of TLP bonds to be determined. Specifically, the article focuses on the production, characterization, and applications of microstructural analogues for TLP bonds in an NiAl/Cu/Ni model system. The article examines the use of five different cast Ni-Al-Cu alloys, together with heat treatment of selected materials, as bulk analogues for six distinct microstructural regions of the NiAl/Cu/Ni bonds. Each of these analogues is characterized in detail by transmission electron microscopy (TEM) and compared to the relevant target region of the bond. An initial examination is also made of the use of bulk alloys in aiding an understanding of phase transformations and structure-property relationships in these bonds.     

Multi-coating inhomogeneities approach for the effective thermo-electro-elastic properties of piezoelectric composite materials

This work presents a micromechanics-based model to predict the effective thermo-electro-elastic properties of a piezoelectric composite materials containing ellipsoidal multi-coated inhomogeneities. A finite element analysis is also performed for two-phase piezoelectric composite materials using ABAQUS finite element software. The results obtained from the multi-coating homogenization method show good agreement with the existing experimental results and the finite element results. The inhomogeneities’s shape effect as well as the poling direction and the coating effects are investigated. The results show that a proper choice of materials and inhomogeneities’s geometry can lead to the desired thermo-electro-elastic properties.     

Corrosion fatigue of some carbon steels in main aqueous environments in Kuwait

Corrosion fatigue of carbon steel 1018 and 4140 was studied in three types of water in Kuwait, potable, brackish and sea water using a rotary fatigue bending machine with a corrosion chamber attached. Results have shown that fatigue strength of both steels is reduced much more in potable water than in brackish water, with maximum reduction occurring in seawater. The low alkalinity and chemical instability of the potable water in Kuwait is a factor that influences the corrosion fatigue of such carbon steels.     

Microstructural development in cast and aged Ni–Al–Cr-based alloys derived from the B2 type β-NiAl structure

The formation of intermetallic compounds consisting of nickel-rich B2-type NiAl (-phase) ductilized by two-phase A1 ()/L12 () regions provides the possibility of combining ductility and high-temperature performance. Similar microstructures can also form the basis of high-temperature shape memory alloys, due to martensitic transformation of the -phase to an L10-type product. One route by which –/ microstructures can be produced involves the use of chromium as a -stabilizer. However, microstructural development in such a case is complicated by the formation of -Cr precipitates.This paper examines microstructural development and stability in cast Ni-25 at % Al-14 at % Cr, Ni-29 at % Al-22 at % Cr and Ni-27 at % Al-8 at % Cr alloys, together with a more complex material, namely, Ni-20 at % Al-13 at % Co-9 at % Cr-4 at % Ti-1 at % Mo-1 at % V. Both the as-cast condition and samples aged at 850 and 1100 °C for 140 h are examined using transmission electron microscopy. The paper discusses the formation of L10 martensite, intradendritic ', interdendritic /' and -Cr precipitation.     

The use of nutshell carbons in drinking water filters for removal of trace metals

Filtration of drinking water by point-of-use (POU) or point-of-entry (POE) systems is becoming increasingly popular in the United States. Drinking water is filtered to remove both organic and inorganic contaminants. The objective of this study was to evaluate the use of granular activated carbon from nutshells (almond, English walnut, pecan) in a POU water filtration system to determine its effectiveness in removing select, potentially toxic metal ions, namely, copper (Cu2+), lead (Pb2+) or zinc (Zn2+) found in drinking water. The nutshell-based carbon system was designated "Envirofilter" and was compared to four commercial POU systems with brand names of BRITA, Omni Filter, PUR and Teledyne Water Pik. Eight prototype "Envirofilters", consisting of individual or binary mixtures of carbons made from acid-activated almond or pecan shells and steam-activated pecan or walnut shells were constructed and evaluated for adsorption of the three metal ions. The results indicated that a binary mixture of carbons from acid-activated almond and either steam-activated pecan or walnut shells were the most effective in removing these metals from drinking water of all the POU systems evaluated. Binary mixtures of acid-activated almond shell-based carbon with either steam-activated pecan shell- or walnut shell-based carbon removed nearly 100% of lead ion, 90-95% of copper ion and 80-90% of zinc ion. Overall the performance data on the "Envirofilters" suggest that these prototypes require less carbon than commercial filters to achieve the same metal adsorption efficiency and may also be a less expensive product.     

Optimizing the distributed generators integration in electrical distribution networks: efficient modified forensic-based investigation

Neural Computing and Applications - As a result of various loads, including critical installations (industries, nuclear facilities, etc.), electrical distribution networks (EDNs) must operate...