Browsing by Author "Ahuja, Y"

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    Friction stir forming to fabricate copper–tungsten composite
    (Elsevier B.V., 2015-03-01) Ahuja, Y; Ibrahim, R; Paradowska, AM; Riley, D
    Tungsten embedded composite of copper (C1100) was fabricated through probeless tool aided friction stir forming (FSF). The heat input conditions and forging were determined to be most effectively controlled by the tool rotation speed. A void-free and continuously bonded Cu–W interface was established at the parameter combination of 1200 rpm tool rotation speed with 100 mm min−1 traverse speed, 0.05 mm plunge and 3° tool tilt angle. The Cu–W interface was characterized via SEM and EDS analysis and was determined to be a purely mechanical interlock due to the absence of new phases. Microstructure of the friction stir formed copper near the interface was examined by optical microscopy. Mechanical properties of the processed copper were investigated by Vickers indentation and shear punch tests, and they showed good correlation with the microstructure. Grain refinement induced work hardening was observed in the copper close to the interface. Cu–W interface remained intact during the shear punch testing and failure occurred in the grain coarsened region of the copper 1 mm away from the interface. The bond strength of the Cu–W mechanical interlock fabricated by FSF was determined to be 130 MPa. © 2014 Elsevier B.V.
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    Industrial application experiments on the neutron imaging instrument DINGO
    (Elsevier, 2017-01-01) Garbe, U; Ahuja, Y; Ibrahim, R; Li, HJ; Aldridge, LP; Salvemini, F; Paradowska, AM
    The new neutron radiography / tomography / imaging instrument DINGO is operational since October 2014 to support the area of neutron imaging research at ANSTO. The instrument is designed for a diverse community in areas like defense, industrial, cultural heritage and archaeology applications. In the field of industrial application it provides a useful tool for studying cracking and defects in concrete or other structural material. Since being operational we gathered experience with industrial applications and commercial customers demanding beam time on DINGO. The instrument is a high flux facility with is 5.3 × 107 [n/(cm2s)] (confirmed by gold foil activation) for an L/D of approximately 500 at HB-2. A special feature of DINGO is the in-pile collimator position in front of the main shutter at HB-2. The collimator offers two pinholes with a possible L/D of 500 and 1000. A secondary collimator separates the two beams by blocking one and positions another aperture for the other beam. The neutron beam size can be adjusted to the sample size from 50 × 50 mm2 to 200 × 200 mm2 with a resulting pixel size from 27 μm to ∼100 μm. The whole instrument operates in two different positions, one for high resolution and one for high speed. We would like to present our first experience with commercial customers, scientific proposals with industrial applications and how to be customer ready. © 2017 The Author(s). Published by Elsevier B.V.
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    Neutron diffraction based non-destructive techniques for integrity studies on copper-stainless steel hybrid composites fabricated by friction stir forming
    (Engineers Australia, 2017-11-27) Ahuja, Y; Abrahams, R; Paradowska, AM
    A novel technique based on probeless tool aided friction stir forming (FSF) has enabled fabrication of bimetallic composites of copper (Cu) with immiscible metals such as tungsten (W) and stainless steel (SS). Thermomechanical bonding of Cu and the embedded SS-insert, with different interfacial geometries and with different intermediate metal powder layers, was investigated. A full 360 tomography of the Cu-SS composites was performed on the neutron imagining station DINGO, at ANSTO. Sequentially stacked neutron images were reconstructed into a 3D model of the sample to examine the existence of voids and tunnel defects. Complete encapsulation and continuous bonding of the SS-insert with thermo-mechanically conditioned Cu established the feasibility of FSF for fabricating such hybrid Cu-SS composites. Additionally, peak temperatures during the process were noted to reach up to 600C, bonding at such temperatures may lock in strain. Furthermore, on cooling significant thermal stresses might develop at the Cu-SS interface owing to the difference in the mechanical properties of two metals. Exposure to continuous heating and cooling cycle during the double pass technique might also result in residual stresses. These stresses occurring as a result of the thermomechanical bonding may affect the integrity of the composite. Owing to the architecturally intricate character of the fabricated Cu-SS hybrid composite, non-destructive neutron diffraction technique of KOWARI strain scanner at ANSTO was utilised. Through-thickness scans across the Cu-SS interfaces were performed using 2 x 2 x 2 mm3 gauge volume. The stress analysis performed in isolated spots of the Cu-SS composite showed minimal variation in the residual stress distribution in all three – longitudinal, traverse and normal directions.© 2017 Engineers Australia
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    Probeless tool aided friction stir welding as a fabrication technique for tungsten embedded mechanical composite of copper
    (The American Society of Mechanical Engineers, 2014-11-18) Ahuja, Y; Ibrahim, R; Paradowska, AM; Riley, DP
    Friction stir welding (FSW) is a relatively new solid state metallurgical joining technique. It flourishes on the simple principle of utilising frictional heat by the stirring motion of a non-consumable rotating tool to create the seam. Feasibility of FSW aided by a newly designed probeless tool was investigated for fabricating copper-tungsten mechanical composite. The most effective parameter combination was determined by conducting a parametric study of the probeless tool aided FSW copper. Strength of the mechanical composite fabricated at this condition was evaluated through punch shear testing. Punch shear testing established that the friction stir welded interface of the copper-tungsten composite was 87% as strong as the base metal (i.e. copper). Advantages of the designed technique have been summarised. © 2014 ASME