Joining of two ferritic oxide-dispersion-strengthened (ODS) alloys, MA956 and PM2000, using transient liquid phase (TLP) bonding is discussed. Thin-film boron coatings of different thicknesses were used as interlayers and different bond orientations with substrates cut along and normal to the direction of extrusion were studied, with postbond heat treatment and microscopic evaluation of the bonds. Microstructural continuity was achieved in bonds when joining fine grain substrates cut along the direction of extrusion.Ferritic oxide-dispersion-strengthened (ODS) alloys are of particular interest in the nuclear industry due to their superior properties, including oxidation resistance, creep resistance, and radiation-induced swelling resistance, compared to austenitic stainless steels and conventional superalloys. [1][2][3][4] The development of an appropriate joining technique is especially crucial for ODS alloys in order to produce a microstructure that is comparable to that of the parent metal, which is free from yttria agglomerates, second-phase particles, and unwanted fine secondary recrystallized grains. The transient liquid phase (TLP) bonding [5,6] shows potential for maintaining parent metal microstructure in bonds between substrates with stable oxide layers.The TLP bonding with different substrate orientations was performed using MA956 (Fe-20Cr-4.5Al-0.5Ti-0.5Y 2 O 3 , wt pct), both in the fine and coarse grain conditions, and PM2000 (Fe-20Cr-5.5Al-0.5Ti-0.5Y 2 O 3 , wt pct), in the fine grain condition. The 11-mm ϫ 10-mm ϫ 2-mm-thick samples were cut normal (transverse) and parallel (longitudinal) to the direction of extrusion, surface ground to a flatness of around 1 m, and then cleaned in an acetone bath. Fine boron interlayers of 1 m, 500 nm, and 250 nm thickness deposited using physical vapor deposition (PVD) were used in the bonding trials; forming a liquid by eutectic reaction with the iron-base substrates. For comparison, bonding was also conducted using a 25-m-thick iron-based (Fe-16B-5Si, wt pct) foil as an interlayer at 1190 °C (above the melting point of the foil). The TLP bonding was performed in a Gleeble (Duffers Scientific Inc., Troy, NY, USA) 1500 thermomechanical processing system in a vacuum of less than 2 ϫ 10 Ϫ3 Pa at 1250 °C under compressive stresses of up to 20 MPa to extrude the excess liquid formed at the bond line. Postbond heat treatments (PBHTs) were performed in a radiantly heated vacuum furnace at 1300 °C for up to 8 hours or 1385 °C for 2 hours for MA956 and PM2000 bonds, i.e., at the respective recrystallization temperatures of the substrate materials. The samples were then etched in a solution consisting of 2 g copper chloride, 40 mL hydrochloric acid, and 40 to 80 mL methanol for 2 to 10 seconds. The microstructural features were then examined by light microscopy and scanning electron microscopy (SEM), the latter employing a JEOL* JSM-840 instrument operated *JEOL is a trademark of Japan Electron Optics Ltd., Tokyo.at 20 kV and energy-dispersive X-ray spectroscopy (EDS).T...

This report presents results of research on advanced joining techniques for ferritic oxide-dispersion strengthened alloys MA956 and PM2000. The joining techniques studied were resistance pressure welding (also known as pressure forge welding), transient liquid phase bonding, and diffusion bonding. All techniques were shown to produce sound joints in fine-grained, unrecrystallized alloys. Post-bond heat treatment to produce a coarse-grained, recrystallized microstructure resulted in grain growth across the bondline for transient liquid phase and diffusion bonds, giving microstructures essentially identical to that of the parent alloy in the recrystallized condition. The effects of bond orientation, boron interlayer thickness, and bonding parameters are discussed for transient liquid phase and diffusion bonding. The report concludes with a brief discussion of ODS joining techniques and their applicability to GEN IV reactor systems.

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Advanced high strength steels (AHSS) are used for car body applications in the automotive industry to improve passenger safety, improve fuel efficiency and to lower harmful carbon emissions. Galvannealed AHSS are used to provide corrosion protection. AHSS are alloyed with several elements such as Mn, Si, Al, P, Mo, etc. to achieve better mechanical properties. However, the knowledge of the effects of Mo on galvannealing behavior is limited. This investigation was conducted to study the influence of molybdenum in steel on galvannealing kinetics. Five dual-phase steels with Mo varying from 0 wt% to 0.4 wt% were used for this study. The results showed a delay in the galvannealing kinetics with an increase in the steel molybdenum content. No obvious improvement in the coating appearance was observed with increasing molybdenum.