High Temperature Oxidation Behavior of Conventional and Nb-Modified MAR-M246 Ni-Based Superalloy

The present investigations focused on the thermal oxidation of two variants of MAR-M246 alloy having the same contents of Ta and Nb in at. pct, considering the effects of total replacement of Ta by Nb. The alloys were produced by investment casting using high purity elements in induction furnace under vacuum atmosphere. The alloys were oxidized pseudo-isothermally at 800 °C, 900 °C and 1000 °C up to 1000 hours under lab air. Protective oxidation products growing on the surface of the oxidized samples were mainly Al₂O₃, Cr₂O₃. Other less protective oxide such as spinels (NiCr₂O₄ and CoCr₂O₄) and TiO₂ were also detected as oxidation products. The conventional alloy exhibited slight internal oxidation at 800 °C and an enhanced resistance at 900 °C and 1000 °C. The Nb-modified alloy presented an exacerbated internal oxidation and nitridation at 900 °C and 1000 °C and an enhanced resistance at 800 °C. At 1000 °C, Nb-modified alloy was particularly affected by excessive spalling as the main damage mechanisms. From a kinetic point of view, both alloys exhibit the same behavior at 800 °C and 900 °C, with k_p values typical of alumina forming alloys (2 × 10⁻¹⁴ to 3.6 × 10⁻¹³ g² cm⁻⁴ s⁻¹). However, Ta modified alloys exhibited superior oxidation resistance at 1000 °C when compared to the Nb modified alloy due to better adherence of the protective oxide scale.

     

Plastic Deformation Resistance of Steel Grades EP450-Sh and EP823-Sh in Hot and Cold State

Metallurgist - The article presents the results of plastometric studies on hot deformation and studies on the hardening curves in cold deformation of EP450-Sh (12H12M1BFR-Sh) and EP823-Sh...     

Cerium Effect on the Phase Composition and Crystallization Behavior of Aluminum Casting Alloys Based on the Al–Mg–Si System

Russian Journal of Non-Ferrous Metals - Using a Thermo-Calc software package (TCAl4.0 database), unexplored data concerning the phase composition and crystallization behavior of...     

Ensuring Strength in Laser Welds Made Using the Dispersion-Hardened EP693 Nickel Alloy

Russian Journal of Non-Ferrous Metals - The process of making a weld using the heat-resistant EP693 alloy (Ni–Cr–W–Co–Co–Mo system) to make assemblies and components...     

Grain Refinement of Casting Aluminum Alloys of the Al–Mg–Si System by Processing the Liquid Phase Using Nanosecond Electromagnetic Pulses

Russian Journal of Non-Ferrous Metals - In this paper, using the AA 511 alloy of the Al–Mg–Si system as an example, it is shown that the irradiation of aluminum melts with nanosecond...     

Equivalent linear limit states

The replacement of any limit state function by an equivalent linear function is discussed in detail and it is shown that there are several methods by which such an equivalence may be established. In the case of multiple failure mode problems the definition of fully equivalent linear functions requires the additional consideration of mode correlations. The manner in which this may be carried out is discussed and it is shown that, for most practical cases, a relatively simple analysis is likely to be sufficient to define the set of equivalent linear limit states, with the advantage that the established theory of such linear limit states may then be employed in the majority of reliability analyses.     

Lead and cadmium in teeth,bone and kidneys of rats with a standard Pb‐Cd supply

Male Wistar rats received a combination of 25 ppm PbCl₂ and 5 ppm CdCl₂ in drinking water at different developmental stages. Pb and Cd levels of incisors, molars, epiphyses, diaphyses and kidney cortex were recorded by atomic absorption spectrophotometry. The results confirmed that Pb has an affinity for hard tissue and especially to teeth, but it also accumulated in soft tissues under the above conditions. In addition, the results indicated none or only a moderate placental or mammary barrier for Pb, and suggested a high absorption of lead from the intestine of sucklings. The results also confirmed that kidney cortex is a primary target for Cd, and indicated that Cd has crossed the placental and mammary barriers to some degree. The positive significant correlation between Cd levels in molars and kidney cortex suggested that rodent molars indicate a degree of Cd absorption, whereas incisors do not. It is supposed that rodent molars are comparable to human deciduous teeth. It is thus confirmed that human deciduous teeth indicate previous lead exposure. It is further inferred that they also can be used as indicators of previous Cd‐exposures.     

Andalusia,Spain: An Assessment of Coastal Scenery

The 1101 km length of the Andalusian coast (Spain) was assessed for coastal scenery at 45 specific locations. Selected areas covered resort (3), urban (19), village (8), rural (10) and remote (5) bathing areas. Scenery was analyzed for physical and human parameters via 26 selected parameters. These parameters were obtained by interviews of >500 people on European beaches. Each parameter was assessed via a one-to-five-point attribute scale, which essentially ranged from presence/absence or poor quality (1), to excellent/outstanding (5). Results were subsequently weighted by interviewing >600 bathing area users (not all 26 parameters have equal weight) and subjected to fuzzy logic mathematics in order to reduce recorder subjectivity. High weighted averages for attributes 4 and 5 (excellent/outstanding) reflected high scenic quality, vice versa for attributes 1 and 2. Sites were classified into five classes ranging from Class 1 sites having top grade scenery to Class 5, poor scenery. Seven sites each were found in Classes 1 and 2; 10 sites each in Classes 3 and 5; 11 sites in Class 4. The finest coastal scenery was found in remote areas whilst urban areas scored mainly as Class 3 or 4. Three out of the ten rural sites had Class 3 and 4 values assigned them whereas the rest scored as Class 1 and 2; village sites invariably had scores within Class 3 and 4. Of the three resort sites investigated, one scored as a Class 1 site, the others as Class 3.     

Town and Country Planning in England's Northeast Section

Abstract

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