Wrought Form Research Articles

Role of metal oxidation at high temperature

ABSTRACT Different cast steels (low-, medium- and high-carbon cast steel) converted into the wrought form by hot rolling and forging processes, the temperature of hot rolling and forging processes are kept 1000°C and then these cast and wrought steel samples prepared and subjected to high temperature oxidation in air under cyclic heating condition for 50 cycles, every cycle consisting of 1-h heating and 20-min cooling. Oxidation kinetics was established by thermo-gravimetric methods by measuring the weight changes at the end of each cycle. The oxidised samples with oxide-scaled surface were investigated for X-ray analysis, scanning electron microscopy (SEM) and Energy Dispersive X-Ray Analysis (EDAX) . All the steel samples suffered oxidation attack in the air which resulted in intense spalling of the oxide scale. It is also observed that the high temperature oxidation rate is maximum for casted samples and is minimum for the rolled samples and for forged samples it lies between cast and rolled steel.

Swinburne

Swinburne Adam Mazel (bio) Swinburne scholarship was relatively quiet this past year; only four essay-length studies will be reviewed in this article. These studies form two themes. Three of the four consider Swinburne’s poetry comparatively, using his verse as a foil to highlight the works of contemporaries and successors who were influenced by but also diverged from Swinburne. The other focus is on examining Swinburne’s ekphrastic poetry in relation to gender norms. Howard J. Booth examines D. H. Lawrence’s derivation and deviation from Swinburne in “‘The Woodland Whose Depths and Whose Heights Were Pan’s’: Swinburne and Lawrence, Decadence and Modernism,” in Decadence in the Age of Modernism, edited by Kate Hext and Alex Murray (Baltimore: Johns Hopkins Univ. Press, 2019). This essay shows that Lawrence’s well-known desire to suture Cartesian dichotomies, such as humanity and nature, emerged from Swinburne’s similar goal, particularly as expressed in such later poems as his 1894 “A Nympholept” and its classical motifs of Pan and nympholepsy, among other mythological tropes. But while Swinburne influenced and was greatly admired by Lawrence, an esteem that was rare among Modernist writers, Lawrence also transcended Swinburne in order to advance his anti-Cartesian aspirations further. Lawrence extends and goes beyond Swinburne’s classical images, loosens his tightly wrought forms, and rethinks his traditional gender relations, making Lawrence, for Booth, the more forward thinking of the two authors. Swinburne’s poetry is also treated comparatively in Julie Casanova’s “Gender and Chronotopes of Revolution in the Border Ballads of Swinburne and Marriott Watson” (VP 57, no. 2 [2019]: 177–199), which argues that the two titular poets have an overlooked poetic relationship. Specifically, Casanova claims Swinburne’s border ballad, “A Song in Time of Revolution, 1860,” from Poems and Ballads, First Series (1866), is critically revised by Rosamund Marriott Watson’s border ballad, “The Quern of the Giants,” from Vespertilia and Other Verses (1895). Marriott Watson’s representation of time and space, for Casanova, is a radical feminist corrective of Swinburne’s representation, which theorizes time and space in a patriarchal and conservative manner, an [End Page 376] argument that Casanova makes via the lens of Mikhail Bakhtin’s chronotope. The poetic form of “A Song in Time of Revolution, 1860,” like many of Swinburne’s poems, is regular and repetitive, and thus it characteristically envisions time as circular, a temporality that Casanova claims is masculinist. “The Quern of the Giants,” on the other hand, employs more metrical variation, which enacts time as more disturbed and disruptive and which, for Casanova, evokes not only revolution but also what she calls the “uncanny feminine” (p. 179). Likewise, Swinburne’s border ballad progressively omits persons to focus on nature, disempowering human agency, whereas Marriott Watson’s ever more focuses on female forces of disruption, a way of undoing masculinist hegemony. Ultimately, then, Swinburne’s ballad is adjudged by Casanova to be conservative and patriarchal; Marriott Watson’s radical and feminist, marking her, for Casanova, as the greater poet. The strength of this essay is its analyses of the form and content of the two poems, but its argument would benefit from further evidence that Marriott Watson’s border ballad is actually a response to Swinburne’s. The final comparative study is Dominique Gracia’s “‘The one question is not what you mean but what you do’: Michael Field’s Ekphrastic Verse” (VP 57, no. 3 [2019]: 345–364). This essay contrasts each of Swinburne’s ekphrastic poems, “A Cameo,” “Hermaphroditus,” and “Before the Mirror,” from Poems and Ballads, First Series, against Michael Field’s ekphrastic “Saint Katharine of Alexandria, by Bartolommeo Veneto,” “Giorgione’s Sleeping Venus,” and “A Portrait, by Bartolommeo Veneto,” from Sight and Song (1892), respectively. Swinburne’s ekphrastic verse, Gracia shows, emphasizes song over sight, suggestion over description, subjectivity over objectivity. Thus, it proves an apt foil for Sight and Song, which Gracia shows does just the opposite, more often prioritizing sight over song by conventionally providing an accurate, detailed description of the art object. Only in “A Portrait” did Michael Field diverge from the artwork being described and thus approach Swinburne’s more experimental, transformative style of ekphrasis. This is...

Evaluation of additive electron beam melting of haynes 282 alloy

The electron beam melting (EBM) process is an attractive additive manufacturing technology that can be applied to a number of different materials. However, fabrication of each material requires tweaking and identifying optimal processing parameters. In this study, process parameters were successively varied to identify a processing regime to fabricate the nickel-base (Ni-base) superalloy Haynes 282. Key parameters to minimize porosity and mitigate the potential for cracking were beam velocity, beam current, hatch spacing, line order, and beam focus. Overall, the EBM process window produced a combination of promising microstructure and 99.5% dense material with no observable cracking. Electron backscatter diffraction revealed a crystallographic texture along the [001] direction of the cube orientation aligned with the build direction. Within the grain interiors of the as-fabricated material were observed uniformly distributed γ′ precipitates with a size distribution ranging from ~80 nm spherical to ~190 nm cuboidal particles with an average particle size of ~128 nm. Grain boundary carbides were observed in two morphologies: blocky and thin film–like. Hardness and tensile testing of the as-fabricated EBM material indicated a 10% higher hardness and slightly lower tensile strength compared with the as-annealed wrought form of the Haynes 282 alloy. The EBM alloy exhibited pronounced ductility except at T > 600 °C perpendicular to the build direction. Annealing based on standard wrought heat treatments showed that γ′ precipitates measuring 20–30 nm in average size can be achieved to improve the alloy's high-temperature performance.

Fabrication of a low alloy ultra-high strength (>1500 MPa yield) steel using powder bed fusion additive manufacturing

In this work, a low alloy ultra-high strength steel is fabricated using powder bed fusion (PBF) additive manufacturing (AM). PBF process parameters and scan strategy to manufacture this ferrous alloy from powder form to fully dense part were successfully developed. Specifically, a process map for laser processing of this material was determined by observing the shape and regularity of the melt pool as a function of laser powers and laser scan speeds using laser profilometry. In addition to processing, mechanical testing and metallurgical examinations using 2D optical and electron microscopy along with the 3D examination of the defect (porosity) structure using micro X-ray computed tomography have been carried out. Since the total volume of detectable pores found throughout the material was negligible, the AM fabrication of the steel is regarded as successful. AM samples were found to have a quasi-static yield strength greater than 1500 MPa, an ultimate strength exceeding 1800 MPa, and 20% elongation in the as-built condition. Significantly, these mechanical properties are superior over the same material in the as-cast conditions and are comparable to those of the wrought form of the material. Details pertaining to processing along with the characterization and testing results are presented and discussed in this paper.

Evolution of Texture during Hot Rolling of a New Magnesium Alloy

High-strength wrought magnesium alloys are one of the sought-after materials in the automotive sector owing to the demands for weight reduction in the automobiles due to fuel economy and CO2 emission. However, because of low room temperature strength and formability of Mg alloys, only a few applications in wrought form have been explored with these materials. In the present investigation, a high strength, good ductility and low cost wrought magnesium alloy with Mg-Sn-Zn composition have been developed and subjected to conventional wrought processing. Hot rolling was carried out at 350°C without homogenization and after homogenization at 300°C and 330°C. The phase stability, microstructure and texture of the alloy has been investigated for as-cast, homogenized and hot rolled conditions. The compositional and microstructural characterization was carried out by Electron Probe Micro-analysis (EPMA) and optical microscopy respectively. Texture evolution was investigated by X-ray diffraction method. A strong (0002) basal texture develops after hot rolling without homogenization. The (0002) basal texture has been weekend by splitting of poles and double peak distribution when hot rolling was carried out after homogenization.

Gas-Atomized Al 6061 Powder: Phase Identification and Evolution During Thermal Treatment

Metal additive manufacturing processes often use gas-atomized powder as feedstock, but these processes use different methods for consolidation. Depending on the consolidation temperature, secondary phases may be retained during processing, making it important to understand powder microstructure prior to consolidation. Commercial alloy compositions are typically used for these powders because they have been widely studied and qualified; however, the microstructure of the powder form of these compositions has not been studied. This paper aims to understand the commercial Al 6061 powder: how the internal microstructure of the powder differs from wrought both in the as-manufactured and thermally-treated conditions. A specific focus is put on the Mg-rich phases and their morphologies. This was accomplished through transmission electron microscopy, scanning transmission electron microscopy, and energy dispersive x-ray spectroscopy. Both the size and morphology of the phases in the powder differ greatly from those in the wrought form.

Mechanical and phase transformation behaviour of biomedical Co-Cr-Mo alloy fabricated by direct metal laser sintering

Biomedical cobalt-chromium-molybdenum (Co-Cr-Mo) alloys have been used in the cast or wrought form as prosthetic implant materials for more than five decades. Recently, additive manufacturing techniques are employed to produce parts directly from metal precursor powder with a composition suitable for biomedical applications. In the work present, we examine both mechanical behaviour and γ→ε phase transformation in the heat treated Co-Cr-Mo alloy fabricated via additive manufacturing route. Results suggest, that selection of appropriate heat treatment and control of martensitic transformation can significantly influence mechanical properties. The studied Co-Cr-Mo alloy can be considered as a potential material for biomedical applications.

The Influence of Post-Build Microstructure on the Electrochemical Behavior of Additively Manufactured 17-4 PH Stainless Steel.

The additive manufacturing (AM) build process produces a segregated microstructure with significant variations in composition and phases that are uncommon in traditional wrought materials. As such, the relationship between the post-build microstructure and the corrosion resistance is not well understood. Stainless steel alloy 17-4PH is an industrially-relevant alloy for applications requiring high-strength and good corrosion resistance. A series of potentiodynamic scans conducted in a deaerated 0.5 mol/L NaCl solution evaluated the influence of these microstructural differences on the pitting behavior of SS17-4. The pitting potentials were found to be higher in the samples of additively-processed material than in samples of the alloy in wrought form. This indicates that the additively-processed material is more resistant to localized corrosion and pitting in this environment than the wrought alloy. The results also suggest that after homogenization, the additively-produced SS17-4 could be more resistant to pitting than wrought SS17-4 in an actual service environment.

“In his old dress”: Packaging Thomas Speght's Chaucer for Renaissance Readers

Abstract This article considers how Thomas Speght's Chaucer editions (1598; 1602) conceive, invite, and influence their readership. Studying the highly wrought forms of the dedicatory epistle to Sir Robert Cecil, the prefatory letter by Francis Beaumont, and the address “To the Readers,” it argues that these paratexts warrant close attention for their treatment of the entangled relationships between editor, patron, and reader. Where prior work has suggested that Speght's audience for the editions was a socially horizontal group and that he only haltingly sought wider publication, this article suggests that the preliminaries perform a multivocal role, poised to readily receive a diffuse readership of both familiar and newer consumers.

Corrosion resistance characteristics of a Ti-6Al-4V alloy scaffold that is fabricated by electron beam melting and selective laser melting for implantation in vivo

The purpose of this study is to determine the corrosion resistance of Ti-6Al-4V alloy fabricated with electron beam melting and selective laser melting for implantation in vivo. Ti-6Al-4V alloy specimens were fabricated with electron beam melting (EBM) and selective laser melting (SLM). A wrought form of Ti-6Al-4V alloy was used as a control. Surface morphology observation, component analysis, corrosion resistance experimental results, electrochemical impedance spectroscopy, crevice corrosion resistance experimental results, immersion test and metal ions precipitation analysis were processed, respectively. The thermal stability of EBM specimen was the worst, based on the result of open circuit potential (OCP) result. The result of electrochemical impedance spectroscopy indicated that the corrosion resistance of the SLM specimen was the best under the low electric potential. The result of potentiodynamic polarization suggested that the corrosion resistance of the SLM specimen was the best under the low electric potential (<1.5V) and EBM specimen was the best under the high electric potential (>1.5V).The crevice corrosion resistance of the EBM specimen was the best. The corrosion resistance of SLM specimen was the best, based on the result of immersion test. The content of Ti, Al and V ions of EBM, SLM and wrought specimens was very low. In general, the scaffolds that were fabricated with EBM and SLM had good corrosion resistance, and were suitable for implantation in vivo.

Fatigue Performance of Powder Metallurgy (PM) Ti-6Al-4V Alloy: A Critical Analysis of Current Fatigue Data and Metallurgical Approaches for Improving Fatigue Strength

A comprehensive assessment of fatigue performance of powder metallurgy (PM) Ti-6Al-4V alloy, manufactured using various powder-based processing approaches to-date, is performed in this work. The focus is on PM processes that use either blended element (BE) or pre-alloyed (PA) powder as feedstock. Porosity and the microstructure condition have been found to be the two most dominant material variables that control the fatigue strength. The evaluation reveals that the fatigue performance of PM Ti-6Al-4V, in the as-sintered state, is far lower than that in the wrought condition. This is largely caused by residual porosity, even if it is present in small amounts, or, by the coarse lamellar colony microstructure. The fatigue strength is significantly improved by the closure of pores, and it approaches the levels of wrought Ti-6Al-4V alloys, after hot-isostatic-pressing (HIPing). Further thermo-mechanical and heat treatments lead to additional increases in fatigue strength–in one case, a high fatigue strength level, exceeding that of the mill-annealed condition, was achieved. The work identifies the powder, process and microstructure improvements that are necessary for achieving high fatigue strength in powder metallurgical Ti-6Al-4V alloys in order for them to effectively compete with wrought forms. The present findings, gathered from the traditional titanium powder metallurgy, are also directly applicable to additively manufactured titanium, because of the similarities in pores, defects, and microstructures between the two manufacturing processes.

Microstructural changes during deformation of AISI 300 grade austenitic stainless steels: Impact of chemical heterogeneity

The present work points out the importance of chemical heterogeneity on the destabilization of austenitic structure and the formation of deformation induced martensite (DIM) in AISI 300 grade austenitic stainless steels (ASSs) of different level of austenite stability (316L, 304, 301LN). Color etching reveals that the structure of wrought Cr–Ni type steels is never fully chemically homogeneous. Confrontation of distribution and morphology of DIM formed in the volume of material after static and cyclic straining under well controlled different conditions with the characteristic local variations in chemical composition of diverse wrought semi-product forms (plates, sheets, bars) proved prominent and very important role of chemical banding in the destabilization of originally fully austenitic structure. This fact should be considered especially when interpreting the results of hydrogen embrittlement tensile testing of Cr–Ni ASSs with lowered Ni content. An impact of chemical heterogeneity on microstructural changes during production of UFG structure of 301LN and its cyclic straining is highlighted.

Additive Manufacturing of 17-4 PH Stainless Steel: Post-processing Heat Treatment to Achieve Uniform Reproducible Microstructure

17-4 precipitation hardenable (PH) stainless steel is a useful material when a combination of high strength and good corrosion resistance up to about 315°C is required. In the wrought form, this steel has a fully martensitic structure that can be strengthened by precipitation of fine Cu-rich face-centered cubic phase upon aging. When fabricated via additive manufacturing (AM), specifically laser powder-bed fusion, 17-4 PH steel exhibits a dendritic structure containing a substantial fraction of nearly 50% of retained austenite along with body centered cubic/martensite and fine niobium carbides preferentially aligned along interdendritic boundaries. The effect of post-build thermal processing on the material microstructure is studied in comparison to that of conventionally produced wrought 17-4 PH with the intention of creating a more uniform, fully martensitic microstructure. The recommended stress relief heat treatment currently employed in industry for post-processing of AM 17-4 PH steel is found to have little effect on the as-built dendritic microstructure. It is found that, by implementing the recommended homogenization heat treatment regimen of Aerospace Materials Specification 5355 for CB7Cu-1, a casting alloy analog to 17-4 PH, the dendritic solidification structure is eliminated, resulting in a microstructure containing about 90% martensite with 10% retained austenite.

Imago Mortis

Imago Mortis Bridget Whearty Mediating Images of Death in Late Medieval Culture. Ashby Kinch. Leiden: Brill, 2013. <http://www.brill.com/imago-mortis> One of the joys of being a medievalist today is the exploding growth of digital access. It seems that every month a new library or museum announces an ambitious digitization program. In the face of this glut of availability, there is a pressing need for smart studies engaging deeply with medieval images. Ashby Kinch’s Imago Mortis: Mediating Image of Death in Late Medieval Book Culture is one such study. Imago Mortis is an ambitious book, exploring cross-pollinations between didactic and literary works, manuscript illumination, wall paintings, cadaver tombs, late medieval religious traditions on the commemoration of the dead, and local and international political maneuvering in England and English-occupied Paris during the 1420s and 30s. Through these nodes, Kinch traces how visual and verbal artists draw on, adapt, and transform each other’s traditions in ways that are sometimes complementary, sometimes competitive, and nearly always in the service of making death more palatable to their powerful patrons. It would have been significantly easier to study one or two of these topics more deeply and in isolation, but it is in teasing out this vast network that Imago Mortis does its most valuable work. As Kinch puts it, “attending closely to the creative re-interpretation of both conventional and novel images of death in the medieval period opens up important dialogues: between literary and visual forms; between artists and the patrons for whom they produced their work; between the political and religious institutions that competed for the psychological and social energies of the late medieval individual; and between ourselves and the past” (276). In Chapter One, “Affirmative Visions of Dying in Illustrations of Henry Suso’s ‘De Scientia,’” Kinch shows how three manuscripts pair Suso’s vision of the lonely bad death with illustrations showing a good end surrounded by community. For the visual artists illuminating these manuscripts, Moriens, the dying one, is supported in death by the same institutions that supported him in life: a good friend (in Bayerische Staatsbibliothek Munchen Cod. gall. 28), a loving family (in Brussels, Bibliothèque Royale, MS IV. III), and an attending cleric (in London, British Library, Additional MS 37049). Rather than dismissing these craftsmen as bad readers of the texts they illustrate, Kinch reads disagreements between Suso’s text and accompanying illustrations as visual [End Page 301] artists’ thoughtful critiques and deliberate transformation of the textual tradition they accompany. Chapter Two, “Verbo-Visual Mirrors of Mortality in Thomas Hoccleve’s ‘Lerne for to Die’” turns to the only extant Middle English verse translation of Suso’s “De Scientia.” Although it begins by analyzing a deathbed illustration in Oxford, Bodleian Library, MS Selden Supra 53, this chapter is not really concerned with connecting Hoccleve’s poem with a specific death culture, visual arts tradition. Instead, it traces how Hoccleve’s verse aestheticizes Suso’s Latin prose, arguing that this highly wrought poetic form serves as a tool for self-promotion, highlighting the English writer and his virtuosity. The chapter concludes by suggesting that Hoccleve differentiates himself from Chaucer through his preoccupation with death and loneliness, Kinch argues that Hoccleve depicts Chaucer as the poet who transcends death, but that he portrays himself as a poet who faces death, thus creating a space for himself outside of Chaucer’s shadow as well as outside the reach of meddling friends and worldly ambition. The intimate links between worldly ambition and patronage are a central topic of Chapter Three, “Commemorating Power in the Legend of the Three Living and the Three Dead,” which analyzes luxury images of the Three Living and the Three Dead. Here Kinch reveals how aristocrats co-opt an art form that began as clerical critique of aristocratic power. Through patronage of exquisite books and monuments, aristocrats turned this satire of their class’s failings to their advantage. The leveling power of death turns out to be something of a lie when patronage is taken into account. All men must die, but the wealthy can purchase rich memorials that ensure the survival of their names and memories, urging those...

The Manifold Singularity of Pearl

I argue that the Middle English Pearl , which survives in just one manuscript, gains literary value from this material uniqueness. By blurring the distinction between scribe and author, this single-manuscript text invites unexpected modes of literary analysis. Physical singularity thus creates wide-ranging, enduring, and in that sense “manifold” interpretive potential. My argument proceeds in three parts. First, I demonstrate that the tension between uniqueness and multiplicity underwrites the poem’s narrative drama and complex lexicon of value; my subsequent investigations are therefore grounded in the concerns of the text itself. I then present close readings of three irregularities in the poem’s highly wrought form. Because we have no other manuscripts to use for comparison, we cannot conclusively designate these irregularities as either scribal error or authorial innovation; this uncertainty creates uncanny resemblances between Dreamer and reader, Pearl-Maiden and Pearl -manuscript. Finally, I analyze modern editorial manipulation of a single contested letter in the manuscript, arguing that Pearl ’s physical uniqueness makes this instance of the literal playful, elusive, and metaphorical. These readings show how interpretive energy can emerge from unknowable historical contingency; this most self-consciously belletristic and beautiful poem thus brilliantly undermines an essentialist understanding of the literary.

Effects of process time interval and heat treatment on the mechanical and microstructural properties of direct laser deposited 316L stainless steel

The mechanical and microstructural properties of 316L stainless steel (SS) fabricated via Direct Laser Deposition (DLD), a laser-based additive manufacturing method, are presented and compared with those of conventionally-built counterparts. Using a Laser Engineered Net Shaping (LENS®) DLD system, the time interval between successive layer deposits, or inter-layer/idle time, for fabricating cylindrical specimens vertically-upward was varied by building either one or nine samples per build plate – thus increasing total assembly volume per build. Subsequently, the effect of thermal history, as well as heat treatment, on microstructural (i.e. grain size and morphology) and mechanical (i.e. tensile, compression, and microhardness) properties of DLD parts were investigated. Results indicate that the DLD 316L SS samples produced herein have a higher yield and ultimate tensile strength relative to their cast and wrought forms. Furthermore, the thermal history, microstructural evolution, and mechanical properties of DLD 316L SS are shown to be dependent on the time interval between deposits. Longer local time intervals result in higher cooling rates, leading to finer microstructures, higher/uniform strength and lower elongation to failure. In addition, porosity and less integral metallurgical bonds are found to be more prevalent in locations further upward from the build plate due to reduced laser penetration depths (e.g. previous-layer remelting decreases). Conversely, parts manufactured with shorter time intervals were found to possess a coarser microstructure, lower strength and higher elongation to failure – attributable to lower cooling rates caused by an increased bulk temperature in the part. These results may aid in future design and control of more efficient, constant-power DLD processes – especially with regard to building multiple and/or larger parts; an approach desirable for minimizing small-to-medium lot production times.

Correlation Between Microstructure and Mechanical Properties in an Inconel 718 Deposit Produced Via Electron Beam Freeform Fabrication

Electron beam freeform fabrication (EBF3), a metallic layer-additive manufacturing process, uses a high-power electron beam in conjunction with a metal feed wire to create a molten pool on a substrate, which on solidification produces a component of the desired configuration made of sequentially deposited layers. During the build-up of each solidified layer, the substrate is translated with respect to the electron beam and the feed wire. EBF3 products are similar to conventional cast products with regard to the as-deposited (AD) microstructure and typical mechanical properties. Inconel 718 (IN 718), a high-temperature superalloy with attractive mechanical and oxidation properties well suited for aerospace applications, is typically used in the wrought form. The present study examines the evolution of microstructure, crystallographic texture, and mechanical properties of a block of IN 718 fabricated via the EBF3 process. Specimens extracted out of this block, both in the AD and in a subsequently heat treated (HT) condition, were subjected to (1) microstructural characterization using scanning electron microscopy (SEM); (2) in-plane elastic modulus, tensile strength, and microhardness evaluations; and (3) crystallographic texture characterization using electron backscatter diffraction (EBSD). Salient conclusions stemming from this study are: (1) mechanical properties of the EBF3-processed IN 718 block are strongly affected by texture as evidenced by their dependence on orientation relative to the EBF3 fabrication direction, with the AD EBF3 properties generally being significantly reduced compared to wrought IN 718; (2) significant improvement in both strength and modulus of the EBF3 product to levels nearly equal to those for wrought IN 718 may be achieved through heat treatment.

Review of type IV cracking of weldments in 9–12%Cr creep strength enhanced ferritic steels

The improvement of thermal efficiency of power plants has provided the incentive for the development of the martensitic–ferritic 9–12%Cr creep-resistant steels. Good progress has been made in developing such steels, which are being used particularly in the wrought form as tubes and pipes for fossil fuelled power stations. They are also finding use in high temperature process plant within the oil and gas sector, and are being considered for use in generation IV nuclear designs. The high temperature conditions that these steels operate under in fossil fuelled power stations induce type IV cracking. This type of cracking occurs in the intercritical or fine grain region of the heated affected zone via a creep mechanism, and results in fractures with relatively little total cross-weld strain. Despite the occurrence of type IV cracking experienced in lower alloy predecessors, successor alloys have been introduced and widely used with insufficient consideration given to the consequences of welding them. Unfortunately, the newer steels suffer from reduced cross-weld creep strength due to type IV cracking to a greater degree in the temperature range of operation expected of them, and thus many failures by this mechanism have occurred. The subject of type IV cracking has been an area of active research interest. This review aims to serve as an update, drawing selectively on some of the vast amount of literature that has been published over the last 30 years.

Development of wrought precipitation strengthened IN939 superalloy

The potential of cast IN939 superalloy to be converted to wrought alloy has been explored in the present work. For this objective, bars of cast alloy were rolled under different conditions and then subjected to various heat treatment cycles. The results indicated that the yield strength, ultimate tensile strength and ductility of the wrought IN939 alloy are superior to the cast version. The stress rupture properties of wrought IN939 superalloy are better than those of the widely used superalloys, such as Nimonic 90 and Waspaloy, and approach the alloy Nimonic 105 properties. This is very notable because Nimonic 105 contains ∼45 vol.-% γ′ that is much greater than the volume fraction of those strengthening precipitates in the alloy IN939 (∼35%). On the whole, the wrought form of this alloy has a high potential for manufacturing hot components to be used safely under aggressive turbine environment.

Fatigue life of ablation-cast 6061-T6 components

The fatigue life of 6061-T6 alloy, normally used in its wrought form, was investigated in this study in cast form from parts produced by the new ablation casting process. All specimens were excised from military castings. Unidirectional tensile test results yielded elongation values comparable to forgings and extrusions. A total of 39 fatigue specimens were tested by the rotating cantilever beam technique at five maximum stress levels. Moreover nine specimens excised from a forging were also tested for comparison. Results revealed that the fatigue life of ablation-cast 6061-T6 (i) follows a three-parameter Weibull distribution, and (ii) is comparable to data from the 6061 forging and is superior to conventionally cast Al-7% Si–Mg alloy castings published in the literature. Analysis of the fracture surfaces of ablation-cast 6061-T6 via scanning electron microscopy showed the existence of fracture surface facets and multiple cracks propagating in different directions.