Metallurgical Studies Research Articles

Quasi-static and Dynamic Fracture of High-strength Aluminium Alloy

The quasi-static and dynamic fracture behaviour of the high-strength aluminium alloy AA7075-T651 was studied by material testing over a wide range of stress states and dynamic impact testing using different shapes of the projectile. Rolled plates of the aluminium alloy exhibited anisotropy owing to the complex, non-recrystallized microstructure. In the quasi-static tests, a marked influence of loading direction on the fracture strain was observed, in addition to the expected strong effect of the stress state. Fragmentation and delamination were observed in the impact tests within the impact zone of the plates. A metallurgical study showed the crack growth to be partly intergranular, along the grain boundaries or precipitation free zones, and partly transgranular by void formation around fine and coarse intermetallic particles.

Finite element and metallurgical study of properties of deformed pure copper by ECAE at various strain rates

In this work, annealed pure copper is deformed by equal channel angular extrusion (ECAE) for a maximum of eight passes. Mechanical properties of the extruded material are obtained at tension velocities of 0.5 mm/min, 200 mm/min and 8 m/s. It is found that the maximum increase of ultimate strength occurs after the second pass for the V = 200 mm/min. The total increase of ultimate strength after eight passes is around 100%. Hardness increases to a maximum of 36% after eight passes. The elongation decreases for the second and fourth passes but increases after sixth and eighth passes. The reason is believed to be due to the formation of equiaxed grains and gradual decrease in dislocation density at the same time after the sixth pass. As the number of equiaxed grains increases, a high rate of dynamic recovery gives rise to further decrease in dislocation density or in other word to decrease in strain hardening. Therefore, after the sixth pass, elongation continues to increase. At the same time, tensile strength also keeps increasing but at a slower rate. Fracture mechanism of extruded specimens was studied at strain rates to a maximum of 4 × 103 s−1. Fractography of specimens shows that fracture mechanism is strain rate independent. ECAE process is simulated using the DEFORM-3D software through a three-dimensional analysis. Grain refinement is simulated by forcing the element size to zero. It is found that for a very fine mesh, the PEEQ converges to 1.51. The value of predicted PEEQs is not rate sensitive and is almost the same for all punch speeds considered in the simulations.

Morphology and metallurgical studies on a few archeological samples found in old forges in Japan

An investigative study was carried out on a few archeological samples collected from very old and abandoned forges situated near Izumo city of Shimane prefecture in Japan. The samples were named as Koedo Tatara (in Japanese) and identified as Koedo-21, Koedo-39 and so on, as per the number of well dug for hunting the samples. In the naked eye observation the samples were looked like the rusted iron lump of heterogeneous shapes having brownish and blackish colours. A variety of minerals such as ilmenite (FeO.TiO2), fayalite (2FeO.SiO2), hercinite (2FeO.Al2O3) along with ferrite (FeO) were identified by observing the structural morphologies in optical microscopic study. EDS (Energy dispersive X-ray spectroscopy) study revealed that most of the samples were the composite of iron oxides along with a few amount of carbon, silica (SiO2), alumina (Al2O3), rutile (TiO2) etc. Vickers micro-hardness test revealed that several samples were moderately hard and some others were nonmetallic oxides and not fit for hardness measurement. It was realized that the samples were the by-product of old blacksmith’s forges which were dismantled for hundreds of years in the natural environment. DOI: http://dx.doi.org/10.3329/jbas.v37i1.15679 Journal of Bangladesh Academy of Sciences, Vol. 37, No. 1, 43-50, 2013

Micro-chemical and metallurgical study of Samnite bronze belts from ancient Abruzzo (central Italy, VIII–IV BC)

The Samnite bronze belts and the chest disk cuirasses (VIII–IV BC) are the distinctive defensive weapons of the Samnite warriors having likely also a symbolic relevance. These artefacts were mainly found during the archaeological excavations of warriors’ graves from ancient Abruzzo (central Italy). Their chemical composition, metallurgical features and corrosion products formed during the long-term burial have been studied by means of the combined use of analytical techniques such as optical microscopy (OM), scanning electron microscopy coupled with energy-dispersive X-ray micro-analysis (SEM–EDS), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD). The micro-chemical and structural results show that the bronze belts have often been produced by using unusual high-tin bronze alloys achieving a silver-like appearance and by performing tailored cycles of thermal treatments under reducing conditions and hot mechanical working aimed to shape the high-tin alloys in the form of a thin bronze sheet. Furthermore, the investigation has shown that the main alloying elements have been transformed during the burial into mineral species giving rise to the formation of stratified structures constituted by different mineral phases such as tin oxides, cuprous oxide (Cu2O) and copper carbonates (azurite (Cu3(CO3)2(OH)2 and malachite (CuCO3Cu(OH)2)) as well as dangerous chlorine-based compounds such as nantokite (CuCl) and atacamite (Cu2(OH)3Cl) polymorphs. This information evidences the strict interaction of the alloying elements with the soil components as well as the occurrence of the copper cyclic corrosion as a post-burial degradation phenomenon. The present study confirms that the combined micro-chemical and micro-structural investigation techniques such as SEM–EDS, XPS, XRD and OM can be successfully used to investigate the technological production processes of the ancient artefacts and to achieve the detailed micro-chemical and structural description of the corrosion products useful for the identification of degradation agents and mechanisms and, thereafter, to propose a reliable tailored strategy for the conservation.

Laser Forming of ERW Steel Square Tubes within Metallurgical Constraints

Laser forming (LF) is a non-contact method to shape metallic sheets and tubes by induced thermal stress without melting using a de-focused laser beam. Laser forming offers the industrial promise of controlled shaping of metallic and non-metallic components for prototyping, correction of design shape or distortion and precision adjustment applications. In order to fulfil this promise in a manufacturing environment the process must have a high degree of control, be repeatable and have a minimal impact on the material and mechanical properties of the part to be formed. In order to demonstrate the capability of the LF process a study is presented in this paper on the 3D Laser Forming of ERW steel square tubes SHS EN10305-5 E220 +CR2 (1.5x25x25mm and 1.5x50x50mm 300mm long tube) using a 1.5kW CO2 laser and industrial 5 axis gantry. Strategies have been developed for out of plane bending with specific emphasis on process throughput balanced with minimising adverse localised changes to material properties that could lead to stress concentration features in a component in service. Presented in this paper is empirical 3D LF shape data verified by a scanning laser profiler, a metallurgical study, hardness testing and a FEM model developed in Comsol Multi-Physics. The results of these studies were employed to develop optimised scan strategies for the controlled laser forming of the ERW steel square tubes within strict metallurgical constraints.

Advanced Solute Conservation Equations for Dendritic Solidification Processes Part I: Experiments and Theory

AbstractThe macrosegregation formed in dendritic equiaxed structure during early stages of solidification of Al‐4.5%Cu alloy has been studied by experimental work and by metallurgical study of cast samples taken from the experimental work. An experimental work was conducted to study the coupled effect of natural convection streams, interdendritic strain and mushy permeability of Al‐4.5%Cu aluminum alloy solidified in horizontal rectangular parallelepiped cavity at different superheats. The metallurgical study includes macro‐microstructure evaluation, measurements of grain size of equiaxed crystals and macrosegregation analysis. This study shows that the level of surface segregation exhibiting as positive segregation varies with superheat whereas the rest of inner ingot areas show the light fluctuation in segregation values. In addition to experimental work, there is a mathematical study which contains a complete derivation of local solute redistribution equations based on Fleming's approach under different solute diffusion mechanisms in the dendritic solid. This derivation includes also the effects of interdendritic strain and mushy permeability on the local solute redistribution distribution. Owing to the length of the study, it is presented in two parts. The first part describes the experimental work and its results as well as a detail derivation of solute conservation equations. This part also involves comparison and discussion between existing and proposed solute conservation equations. The second part contains the mathematical analyses of a two dimensional mathematical model of fluid flow, heat flow, solidification, interdendritic strain and macrosegregation. Also, this part also contains the numerical simulations by using finite difference technique “FDT” to create convection patterns, heat transfer, interdendritic strain, and macrosegregation distributions. This part also includes comparisons between the available measurements and model predications as well as full discussion of different model simulations. The mechanism of interdendritic strain generation and macrosegregation formation during solidification of dendritic equiaxed structure under different diffusion mechanisms in dendritic solid has also been explained and discussed.

Physical Metallurgical Studies of Zr-Rich U-Zr Alloys

Uranium-zirconium alloy is considered main ingredient for making metallic fuel for Fast Breeder Reactor. Also, Zr-rich U-Zr alloys find applications in dispersion fuel for advance PWR. In this work investigations were carried out on the zirconium rich uranium-zirconium alloys (i.e. U-50wt%Zr, U- 60wt%Zr and U-70wt%Zr) in as-cast as well as in heat treated conditions. Microstructural and dilatometric studies were carried out along with X-ray Diffraction Analysis (XRD) to evaluate the phase content as well as the phase transformation behavior of these alloys under different heat treated conditions.

ProFile Vortex Instruments after Clinical Use: A Metallurgical Properties Study

IntroductionThe aim of the study was to analyze the incidence and mode of ProFile Vortex instrument (Dentsply Tulsa Dental Specialties, Tulsa, OK) defects during a predefined schedule of clinical use by the undergraduate students in a dental school setting and to examine the metallurgical characteristics of unused and clinically used Vortex instruments. MethodsA total of 2,203 ProFile Vortex instruments discarded after single use from the undergraduate students program over 24 months were collected and examined for defects using a stereomicrosocpe at 10× magnification. The incidence and type of instrument defects or separation were analyzed. The lateral surfaces of part of the defected instruments and fracture surfaces of fractured files were examined using scanning electron microscopy. Unused and clinically used files were examined by differential scanning calorimetry and X-ray diffraction. Vickers hardness of the files was measured with a 200-g load. ResultsOnly 1 of the 2,203 files fractured during clinical use. The cause of fracture was shear stress, and the file also showed unwinding of the helix structure. None of the remaining 2,202 files exhibited unwinding after clinical use. Blunt apicals were detected in 86 used files (3.9%). Austenite-finish temperatures were very similar for as-received, used files with defects and used files without defects, all exceeding 50°C. No difference in microhardness was detected among these 3 instrument groups. X-ray diffraction results showed that NiTi files had austenite structure at room temperature. ConclusionsThe risk of ProFile Vortex fracture is very low when files are used 1 time by undergraduate students. Unwinding of the files was not detected except for the fractured file. Clinical single use had no detectable effect on austenite-martensite phase transformation of the files. Unused and clinical single-use files contain a similar phase structure at body temperature.

Analysing the properties of hardened surfaces of knots’ parts of repair-technological equipment

The basics of parts surfaces’ hardening are given. Basic dependences of hardening are presented. Sequential determination of surface quality is given, metallurgical studies of hardened samples are carried out.

From Coin to Medal: A Metallurgical Study of the Brazing Drop on a 19th Century Scudo

In the past, it was customary to use out-of-circulation coins as pendants by brazing a peg or ring on the edge of the coin in order to transform it into a devotional or decorative object; this practice was very common for specimens of the Papal States, especially for silver coins. This metallurgical investigation of a 19th century Scudo aimed to relate the internal structure of the coin to the minting technology with a special focus on the brazing drop, in order to provide information on the solidification microstructure arising from a strongly nonequilibrium process such as brazing. The results show that the Ag content in the coin ranges from 92% in the bulk up to 97% on the surface, due to enrichment, while analysis of the brazing revealed that it consists of an Ag-Cu-Zn-Pb alloy, for which the melting temperature has been estimated. Considering the distribution of minor elements, Zn segregates in the secondary (Cu-rich) β-dendrites and inside the whole eutectic structure, while Pb is only present in the Ag-based phases and seems to reduce the solubility of Zn inside the primary (Ag-rich) α-dendrites.

The metallurgy, mechanics, modelling and assessment of dissimilar material brazed joints

At the heart of any procedure for modelling and assessing the design or failure of dissimilar material brazed joints there must be a basic understanding of the metallurgy and mechanics of the joint. This paper is about developing this understanding and addressing the issues faced with modelling and predicting failure in real dissimilar material brazed joints and the challenges still to be overcome in many cases. An understanding of the key metallurgical features of such joints in relation to finite element modelling is presented in addition to a study of the mechanics and stress state at an abrupt interface between two materials. A discussion is also presented on why elastic singularities do not exist based on a consideration of the assumption of an abrupt change in material properties and plasticity in the vicinity of the joint. In terms of modelling real dissimilar material brazed joints; there are several barriers to accurately capturing the stress state in the region of the joint and across the brazed layer and these are discussed in relation to a metallurgical study of a real dissimilar material brazed joint. However, this does not preclude using a simplified modelling approach with a representative braze layer in design and failure assessment away from the interface. In addition modelling strategies and techniques for assessing the various failure mechanisms of dissimilar material brazed joints are discussed. The findings from this paper are applicable to dissimilar material brazed joints found in a range of applications; however the references listed are primarily focussed on work in fusion research and development.

Influence of Y2O3 particles on mechanical properties of magnesium and magnesium alloy (AZ91D)

Nowadays, research studies and industrial requirements are directed toward the goals of achieving environmental friendliness, energy savings, and reduced weight. Magnesium and magnesium alloys are well suited for structural and automotive applications owing to their lightweight. However, the reduced hardness and strength of these alloys do pose problems in exploiting their usage. These impediments of lightweight metal matrix can be alleviated by reinforcing hard-phase particles. Different volume percentages of Y2O3 particles (average grain size 5 µm) were added as reinforcements in pure magnesium and magnesium alloy (AZ91D) and the composites were processed through the two-step stir-casting technique. Mechanical and metallurgical characterization studies were carried out on the stir-cast composites under as-cast and heat-treated conditions. Uniform distribution of yttria particles in magnesium and magnesium alloy matrix was observed through scanning electron micrographs. Macro and microhardness tests revealed the increased hardness with the increased amount of yttria reinforcement.

Failure Investigation of Natural Gas Pipeline

A study was carried out to investigate the probable cause or events that might have led to the failure of two parallel natural gas pipes, API 5L X42 carbon steel (NPS 8) and the SDR 17, 125 mm medium density polyethylene pipes. These two pipes were laid side by side in the same trench with a water pipe. The investigation was performed by analyzing the existing design and construction data, visual inspection of failed pipes, and pipe material analysis. Investigation from the relevant pipes data suggests that the leaked water pipe was the first to fail. The leaked water pipe created high pressure water jetting that mixed with the backfilling soil to form water–sand–soil slurry with high erosive properties. The impact of this erosive slurry upon the NPS 8 pipe had caused serious losses of pipe coating materials. This phenomenon explains the rapid thinning of the steel pipe body which later led to its failure. Evidence from the metallurgical study using photomicrograph showed that the morphology of the steel material was consistent and did not show any evidence of micro fractures.

Metallurgical Studies on the Friction Stir Welding of Dissimilar A356 and A413 Alloys

Friction stir welding is a technique useful for joining aluminum alloys that are difficult to weld. In recent years, however the focuses has been on welding dissimilar aluminum alloys, and analyze their mechanical properties and micro-structural characteristics. In the present study, the less investigated welding of cast aluminum alloys is considered. Cast aluminum alloys, A356 and A413, commonly used in automotive and aerospace industries, were friction-stir welded and their mechanical properties and micro-structural characteristics were analyzed. On testing their welded region, no welding defects were observed. The welded region exhibited a maximum tensile strength of 90 N/mm2 and Vickers micro-hardness of 56.8. The micro-structural observations at the nugget region revealed a refined grain structure.

Failure investigation of wheel gear hub assembly of an aircraft

The failure investigation of an aircraft rear wheel gear hub at hood position was conducted to find the cause of fracture. The stereographs represented river pattern at crack initiation site originating from the preexisting cracks at the inner surface of hood. The metallurgical study showed the overaging of wheel hub material. Stress analysis by finite elemental analysis identified the stress concentration regions nearly at the same positions of wheel hub from where it was failed in reality. The SEM analysis of fracture surface represented that crack propagated by cleavage mode with microvoid coalescence at the eutectic and α-Mg interface. The overloading was a cause of final failure with visible features of chevron marks pointing back in the direction of crack originating site.

Archeaometallurgical finds from Barsinia, Northern Jordan: Microstructural characterization and conservation treatment

Abstract Within the framework of an excavation project aimed to systematically characterize the various aspects of settlement and activities in Northern Jordan, a considerable collection of slag lumps and iron artifacts of different forms and typologies excavated from the archaeological site of Barsinia were collected. Excavations have revealed other metallurgical materials such as pottery tuyeres and furnace-like structure. Studying those finds was important because of their archaeological and technological interests. For the analytical and metallurgical study, X-ray diffraction was used to identify the mineralogical composition of samples. Inductively coupled plasma-optical emission spectrometer, energy dispersive X-ray and X-ray fluorescence spectrometer were used to determine the accurate elemental composition of these finds. Furthermore examinations by using metallographic, polarizing microscope and scanning electron microscopy were employed to diagnose the characteristic morphology and environmental effects of these archaeometallurgical finds. Microstructural investigations emphasized that iron production processes were performed locally at the archaeological site of Barsinia even if the iron ores were imported from other mining location in Jordan. Direct or “bloomer” was the main method used for smelting iron ores followed by smithing methods to locally produce iron artifacts. This, most probably, was the state of technology from the Bronze Age to the Byzantine period. To ensure the stability of these deteriorated finds for future research, required treatment and conservation processes were successfully carried out.

Experimental and finite element simulation study of the adiabatic shear band phenomenon in cold heading process

This paper presents the outcomes of a comprehensive experimental, metallurgical and finite element (FE) simulation study to characterize the development of adiabatic shear band (ASB) phenomenon in steel cold heading (CH) process. The main objective of this work is to investigate the complex interplay of different process and material parameters on the ASB development stages inside the cold headed parts.In this work, the drop weight compression test (DWCT) was selected to simulate the CH process impact loads on specimens machined from 1038 steel and 1018 steel. Series of DWCTs were performed under different impact loading conditions. The goal of these tests is to achieve different deformation levels and introduce ASBs at different stages.To reach a full understanding of this complex phenomenon, the FE simulation analysis was used to support the metallurgical examination of the DWCT specimens. The FE analysis provided important details about the changes of different material and process parameters at the critical zones inside the ASBs.This study confirmed that the ASB is mainly a thermo-mechanically controlled phenomenon. The ASBs develop in three stages: homogeneous plastic strain, inhomogeneous plastic strain, and strain localization. The ASB development stage depends mainly on the status of the competition between the work hardening and the thermal and geometrical softening mechanisms inside the bands. The domination of the softening mechanisms at advanced levels of deformation triggers a self-catalytic strain localization and material strength degradation process that leads to failure inside the band.In general, the metallurgical and finite element analysis investigation revealed that under impact loads, three ASBs can develop simultaneously inside the cold headed parts; lower, upper and central ASBs. As the deformation continues; the development of the lower and upper bands slows down and contributes in the rapid development of the adjacent central ASB. This study confirmed that the ASB has a canonical structure which leads to an ASB that can experience different development stages along the same band simultaneously.This study proved that the shape and the type of ASBs in cold headed parts depend highly on material's properties. The metallurgical and finite element analysis revealed that the higher the strength of the tested steel, the easier to form a narrow ASB that reaches the localization stage at low deformation levels. In contrast, ductile steels experience wider ASBs when subjected to the same deformation levels. These bands require higher levels of deformation to reach the localization stage in comparison to higher strength steels.

Innovative Techniques in Non-Destructive Testing and Industrial Applications on Pressure Equipment

Abstract The average age of pressure vessels in service worldwide is increasing from year to year. A major concern of industrial operators is to ensure the security of their facilities and people, while extending the life of their fleet of pressure vessels. In this context, it is necessary to control the health of this type of structure, and also be able to assess the residual life of a device. Through a real case, the study presented in this article shows all the stages of implementation of a process that allowed initially to make an accurate diagnosis of the condition of a sphere of storage and to evaluate its lifetime, then in a second time, to ensure the operations back into compliance to ensure a reactivation of this structure. This process is fully insured by the CETIM, involved the following: • A hydraulic test with acoustic emission monitoring, • Testing additional relevant Non Destructive testing (NDT) (TOFD, Ultrasonic, Magnetic ...) • Checks by the method of metallographic replicas and/or levies, • A study of life, estimated by calculations based on NDT and metallurgical studies, • Writing a procedure recommendations repair by welding of critical defects, • The supervision during repairs and the testing after repairs. This approach is developed by Cetim based on Innovative Non destructive testing.

Naipes (axe moneys): a pre-Hispanic currency in Peru

Between AD 900 and 1100 in northern Peru, high-status members of the Middle Siccin culture were buried in large tombs accompanied by elaborate grave goods that included gold, silver and copper objects, and also pieces of sheet metal known as naipes. Metallurgical study of naipes at the Institute supports the view that they were a form of primitive money.

Metallurgy: Understanding How, Learning whY. Studies in Honor of James D. Muhly ed. by Philip P. Betancourt, Susan C. Ferrence (review)

Reviewed by: Metallurgy: Understanding How, Learning whY. Studies in Honor of James D. Muhly ed. by Philip P. Betancourt, Susan C. Ferrence David W. Rupp Philip P. Betancourt and Susan C. Ferrence, eds. Metallurgy: Understanding How, Learning whY. Studies in Honor of James D. Muhly. Prehistory Monographs 29. Philadelphia: INSTAP Academic Press, 2011. Pp. xxxii + 304. US$80.00. ISBN 9781931534574. In this era of hyper-specialization in archaeological research in the Mediterranean region, few individuals can claim to have engaged in research spanning from the Italian peninsula to Mesopotamia that includes as well the Bronze and Early Iron Ages. One of these rare birds is James D. Muhly. His interest in and knowledge of ancient literature and history, field archaeology and scientific analyses of metal objects have given him this amazing range of expertise. Muhly obviously was not afraid to venture into new areas of inquiry during his 45-year career. With such a broad background he has cultivated an extensive network of collaborators and colleagues. Under the editorship of Betancourt and Ferrence the volume under review has been published to honour his many accomplishments. The thought-provoking title cleverly spells out Muhly with strategically placed capital letters. Muhly was a dedicated and persistent researcher, as the seven pages of his bibliography attest. With this in mind, his zest for living and his family is lovingly reinforced in his wife’s review of his life and career. Polymnia (Poly) Metaxa-Muhly is an accomplished archaeologist in her own right. Ferrence’s introduction contextualizes all of this while also presenting the many reasons for offering this Festschrift to him. Thirty-eight individuals (some as co-authors as well as single authors) have contributed 28 papers relating in some way to metallurgical studies involving copper, tin, bronze, silver, gold, and iron spanning from the beginning of the fourth to the beginning of the first millennia bc. The papers are [End Page 89] organized into four broad thematic approaches: the metallurgy of Cyprus, the metallurgy of Crete, metallurgical technology, and trade and interaction in the history of metallurgy. These, of course, reflect Muhly’s own research interaction spheres. Edited volumes with so many contributions are very difficult to review in a limited space. In essence, a reviewer presents either a shopping list of names and titles or the best/most interesting papers from her point of view. I will aim for a middle way here. The seven papers related to Cyprus start with the earliest evidence for copper-working in the Middle and Late Chalcolithic Period in the southwest part of the island (E. Peltenburg). A small corpus of 12th-century bc miniature ox-hide copper ingots inscribed with Cypro-Minoan signs mostly found near the Sanctuary of the Horned God Enkomi (A. Giumlia-Mair and V. Kassianidou) and one from Alassa (S. Hadjisavvas) reveal the complex associations that religion and cult had with metal production on the island. The changing iconography of the heavily armed Ingot God (also from Enkomi) from a smiting god in LC IIC to a smithing god with the addition of a miniature ox-hide ingot in LC IIIB mirrors the evolving socio-economic organization and belief systems in the settlement related to metallurgy before its abandonment (G. Papasavvas). The introduction of ceramic tuyères and bellows to the island in LC I revolutionized the Cypriot copper industry by increasing the amount of copper that could be produced by improving the effectiveness of the smelting process (V. Kassianidou). The site of Athienou–Pamboularin tis Koukouninas has produced evidence for large-scale elite feasting in association with the metallurgical industry (V. Karageorghis). In addition to local ceramics, imported LM IIIB and LH IIIB vessels were used. An early example (now in Florence) from Cyprus of a miniature cast copper-rod tripod-stand with a hemispherical copper bowl dating to ca. LC I probably was used as an incense burner (F. Lo Schiavo). For Crete the seven papers focus on various classes of bronze, silver, and gold artifacts (C.E. Galanaki, Y. Bassiakos, and V. Perdikatsis; J. Hickman; P.P. Betancourt; J.S. Soles) including an update by K. Branigan on the EM I so-called cast bronze triangular...