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The purpose of this paper is to present the effect of the aging at 200°C on creep and hardening behavior of hardenable 6101 aluminum alloy manufactured by an industrial wiredrawing process used for construction of self-supporting overhead aerial power line conductors.

The creep tests were carried out under applied constant stress 100 MPa and constant temperature 150°C. Hardness measurements were also used to investigate the mechanical behavior of the aged alloy. Micrographs of the fractured wires by creep tests were performed by scanning electron microscope. Electrical resistivity of the aged alloy was measured at different time of the aging treatment.

The authors have found the relationship between the precipitation sequence, the mechanical properties and the electrical resistivity of aged 6101 aluminum alloy.

The optimum properties were also deduced.

The purpose of this paper is to discuss the recently developed multi-physics computational model for the conventional Gas Metal Arc Welding (GMAW) joining process that has been upgraded with respect to its predictive capabilities regarding the spatial distribution of the mechanical properties controlling the ballistic limit (i.e. penetration resistance) of the weld.

The original model consists of five modules, each dedicated to handling a specific aspect of the GMAW process, i.e.: electro-dynamics of the welding-gun; radiation-/convection-controlled heat transfer from the electric arc to the workpiece and mass transfer from the filler-metal consumable electrode to the weld; prediction of the temporal evolution and the spatial distribution of thermal and mechanical fields within the weld region during the GMAW joining process; the resulting temporal evolution and spatial distribution of the material microstructure throughout the weld region; and spatial distribution of the as-welded material mechanical properties. The model is upgraded through the introduction of the sixth module in the present work in recognition of the fact that in thick steel GMAW weldments, the overall ballistic performance of the armor may become controlled by the (often inferior) ballistic limits of its weld (fusion and heat-affected) zones.

The upgraded GMAW process model is next applied to the case of butt-welding of MIL A46100 (a prototypical high-hardness armor-grade martensitic steel) workpieces using filler-metal electrodes made of the same material. The predictions of the upgraded GMAW process model pertaining to the spatial distribution of the material microstructure and ballistic-limit-controlling mechanical properties within the MIL A46100 butt-weld are found to be consistent with general expectations and prior observations.

To the authors’ knowledge, the present work is the first reported attempt to establish, using computational modeling, functional relationships between the GMAW process parameters and the mechanical properties controlling the ballistic limit of the resulting weld.

The susceptibility of 17‐4PH and 17‐7PH stainless steels to stress corrosion cracking (SCC) is examined in the present investigation. The specimens were tested in the presence of NaCl and NaOH (20%) at 908C and various pH values. The evaluations were carried out using the CERT test, at a speed of 10^‐6s^‐1, supplemented by anodic polarisation and electrochemical noise analysis. The main objective was to identify the conditions of both susceptibility and performance of these materials. Fractographic analyses revealed both ductile and brittle fractures. Also, the presence of intergranular cracks was a clear indication of a characteristic anodic dissolution of the material. Nevertheless, the main mechanism for stress corrosion crack propagation was hydrogen embrittlement. From the experimental results, it was concluded that electrochemical noise analysis is a reliable technique for the identification of crack nucleation and growth.

The weld region obtained during friction stir welding (FSW) of metallic materials (including aluminum alloys) contains typically well-defined zones, each characterized by fairly unique microstructure and properties. The purpose of this paper is to carry out combined experimental and numerical investigations of the mechanical properties of materials residing in different weld zones of FSW joints of thick AA2139-T8 plates.

Within the experimental investigation, the following has been conducted: first, optical-microscopy characterization of the transverse sections of the FSW joints, in order to help identify and delineate weld zones; second, micro hardness field generation over the same transverse section in order to reconfirm the location and the extent of various weld zones; third, extraction of miniature tensile specimens from different weld zones and their experimental testing; and finally, extraction of a larger size tensile specimen spanning transversely the FSW weld and its testing. Within the computational investigation, an effort was made to: first, validate the mechanical properties obtained using the miniature tensile specimens; and second, demonstrate the need for the use of the miniature tensile specimens.

It is argued that the availability of weld-zone material mechanical properties is critical since: first, these properties are often inferior relative to their base-metal counterparts; second, the width of the weld in thick metallic-armor is often comparable to the armor thickness, and therefore may represent a significant portion of the armor exposed-surface area; and finally, modeling of the weld-material structural response under loading requires the availability of high-fidelity/validated material constitutive models, and the development of such models requires knowledge of the weld-material mechanical properties.

The importance of determining the mechanical properties of the material in different parts of the weld zone with sufficient accuracy is demonstrated.

This study aims to reveal that fatigue life is improved using heat treatment in the rotational bending fatigue test, which determines the fatigue behavior closest to service conditions.

It is essential to know the mechanical behavior of the parts produced by additive manufacturing under service conditions. In general, axial stress and plane bending tests are used by many researchers because they are practical: the service conditions cannot be sufficiently stimulated. For this reason, the rotating bending fatigue test, which represents the conditions closest to the service conditions of a load-bearing machine element, was chosen for the study. In this study, the rotational bending fatigue behavior of X3NiCoMoTi18-9–5 (MS1) maraging steel specimens produced by the selective laser melting (SLM) technique was experimentally investigated under various heat treatments conditions.

As a result of the study, MS1 produced by additive manufacturing is a material suitable for heat treatment that has enabled the heat treatment to affect fatigue strength positively. Cracks generally initiate from the outer surface of the sample. Fabrication defects have been determined to cause all cracks on the sample surface or regions close to the surface.

While producing the test sample, printing was vertical to the print bed, and various heat treatments were applied. The rotating bending fatigue test was performed on four sample groups comprising as-fabricated, age-treated, solution-treated and solution + age-treated conditions.

Most literature studies have focused on the axial fatigue strength, printing orientation and heat treatment of maraging steels produced with Direct Metal Laser Sintering (DMLS); many studies have also investigated crack propagation behaviors. There are few studies in the literature covering conditions of rotating bending fatigue. However, the rotating bending loading state is the service condition closest to modern machine element operating conditions. To fill this gap in the literature, the rotating bending fatigue behavior of the alloy, which was maraging steel (X3NiCoMoTi18-9–5, 1.2709) produced by SLM, was investigated under a variety of heat treatment conditions in this study.

Brief Particulars of Recently Introduced Materials likely to have Aircraft, Missile or Space Vehicle Applications. A new ice warning system for aircraft using equipment incorporating printed circuits based on copperclad Bakelite laminate, has been developed by Teddington Aircraft Controls Ltd., Merthyr Tydfil.

The problem of hydrogen embrittlement has been approached in a less theoretical manner than in some previous investigations. Factors were considered which could be utilized to minimize embrittlement in processing especially with the higher strength steels which suiter mostly.

The purpose of this paper is to present results of laboratory testing work on causes of a service failure/damage to an aircraft turbojet's gas‐turbine blade made of the EI 867‐WD alloy.

The tests comprised comparing the microstructure of a service‐damaged blade with microstructures of specimens drawn from a similar all‐new blade, both subjected to temperatures of different values for different annealing times.

Findings based on the comparison of experimentally gained results of microstructure examination of both the gas‐turbine blades were: the change in the microstructure of a damaged blade results from the growth and cuboidal‐to‐lamellar change of shape of the reinforcing phase γ′ (Ni₃Al); and the size and shape of this phase are comparable to those of the phase γ′ of a new blade subjected to annealing at temperature exceeding 1,223 K for 1 h. The results gained allowed for drawing the conclusion that the damaged turbine blade was operated in the exhaust‐gas temperature exceeding the maximum permissible value of 1,013 K for approximately 1 h in the course of an air mission.

The comparison‐oriented experimental testing work was carried out on a new blade manufactured in the way and from material identical to those of the damaged blade. The applied methodology enables us to gain qualitative results of investigating into the causes of a failure/damage to a gas‐turbine blade.

The presented methodology of identifying (origin‐finding of) a service‐induced damage to a gas‐turbine blade proves helpful in the case of an engine failure, when information on the operating conditions thereof is insufficient.

The paper is an original work by the authors. To the best of their knowledge, the issue has not been found in the literature, approached in this particular way. It has been based on research work on air accidents due to the service‐induced failures/damages to gas‐turbine blades in aircraft turbojet engines.

The purpose of this paper is to evaluate and compare powder and wire laser material deposition (LMD) processes.

In the present paper, Inconel 718 tensile test probes were built layer by layer using a longitudinal strategy, and the quality of the deposited material was characterized for both wire and powder LMD processes. The measured data during the deposition tests have been used for comparing the efficiency of both powder and wire LMD processes. Afterwards, to evaluate the mechanical properties of the parts generated by means of both processes, standard tensile tests were carried out. Furthermore, other factors have been evaluated, such as process reliability or presence of residual material, after the deposition process.

Results show a higher efficiency of the wire LMD process, and even similar ultimate tensile stress values were reached for both processes; powder LMD parts resulted in a more brittle nature.

In the present paper, a thorough analysis that compared both processes has been carried out. The results obtained will help in the future when choosing between wire and powder LMD. The main points of the wealth of knowledge generated with these research efforts are highlighted herein.

The purpose of this paper is to design and develop precipitation hardened Al-Mg alloy imparting enhanced strength with acceptable ductility through minor addition of Sc and Cr by using multi-objective genetic algorithm-based searching. In earlier attempts of strengthening aluminum alloys, owing to the formation of Al₃Sc and Al₇Cr phase, addition of Sc and Cr have yielded attractive precipitation hardening, respectively. Both the Al-Sc and Al-Cr system are quench sensitive due to presence of a sloping solvus in their phase diagrams. It is also known that both the Al₃Sc and Al₇Cr phases nucleate directly from the supersaturated solid solution without formation of GP-zones or transient phases prior to the formation of the Al₃Sc and Al₇Cr. Sc also found to have beneficial effect on the corrosion property of such alloys. In view of the above, it is of interest to explore the possibility of enhancing the age hardening effect in Al-Mg alloy by addition of Sc and Cr.

The paper uses an approach where experimental information of two different alloy systems (namely, Al-Mg-Sc and Al-Cr) has been combined to generate a single database involving the potential features of both the systems with the aim to formulate the suitable artificial neural network (ANN) models for strength and ductility. The models are used as the objective functions for the optimization process. The patterns of the optimized Pareto front are analyzed to recognize the optimal property of the alloy system. The hitherto unexplored Al-Mg-Sc-Cr alloy, designed from the Pareto solutions and suitably modified on the basis of prior knowledge of the system, is then synthesized and characterized.

The paper has demonstrated the ANN- and genetic algorithm (GA)-based design of a hitherto unexplored alloy by utilizing the existing information concerning the component alloy systems. The paper also established that analyses of the Pareto solutions generated through multi-objective optimization using GA provide an insight of the variation of the parameters at different combination of strength and ductility. It also revealed that the Al-Mg-Sc-Cr alloy has exhibited a two-stage age hardening effect. The first and second stages are due to the precipitation of Al₃Sc and Al₇Cr phases, respectively.

In the present study the two alloy systems are used in tandem to develop models to describe the properties involving the distinct mechanistic features of phase evolution inherent in both the systems. Though the ANN models having the capability to capture huge non-linearity of a system have been employed to predict the convoluted effects of those characteristics when an alloy containing Mg, Sc and Cr are added simultaneously, but the ANN models predictions can be checked experimentally by the future researchers.

The paper demonstrates the role of scandium and chromium addition on the ageing characteristics of the alloy by analyzing the age hardening behavior of the designed alloy in cast and cold rolled condition clearly.

The approach stated in this paper is a novel one, in the sense that experimental data of two different alloy systems have been clubbed to generate a single database with the aim to formulate the suitable ANN models for strength and ductility.