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Banbury, United Kingdom

Scamans G.M.,Innoval Technology | Scamans G.M.,Brunel University
Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science | Year: 2011

Intergranular sustained-load cracking of Al-Zn-Mg-Cu (AA7xxx series) aluminum alloys exposed to moist air or distilled water at temperatures in the range 283 K to 353 K (10 °C to 80 °C) has been reviewed in detail, paying particular attention to local processes occurring in the crack-tip region during crack propagation. Distinct crack-arrest markings formed on intergranular fracture faces generated under fixed-displacement loading conditions are not generated under monotonic rising-load conditions, but can form under cyclic-loading conditions if loading frequencies are sufficiently low. The observed crack-arrest markings are insensitive to applied stress intensity factor, alloy copper content and temper, but are temperature sensitive, increasing from ∼150 nm at room temperature to ∼400 nm at 313 K (40 °C). A re-evaluation of published data reveals the apparent activation energy, E a for crack propagation in Al-Zn-Mg(-Cu) alloys is consistently ∼35 kJ/mol for temperatures above ∼313 K (40 °C), independent of copper content or the applied stress intensity factor, unless the alloy contains a significant volume fraction of S-phase, Al 2CuMg where E a is ∼80 kJ/mol. For temperatures below ∼313 K (40 °C) E a is independent of copper content for stress intensity factors below ∼14 MNm -3/2, with a value ∼80 kJ/mol but is sensitive to copper content for stress intensity factors above ∼14 MNm -3/2, with E a, ranging from ∼35 kJ/mol for copper-free alloys to ∼80 kJ/mol for alloys containing 1.5 pct Cu. The apparent activation energy for intergranular sustained-load crack initiation is consistently ∼110 kJ/mol for both notched and un-notched samples. Mechanistic implications are discussed and processes controlling crack growth, as a function of temperature, alloy copper content, and loading conditions are proposed that are consistent with the calculated apparent activation energies and known characteristics of intergranular sustained-load cracking. It is suggested, depending on the circumstances, that intergranular crack propagation in humid air and distilled water can be enhanced by the generation of aluminum hydride, AlH 3, ahead of a propagating crack and/or its decomposition after formation within the confines of the nanoscale volumes available after increments of crack growth, defined by the crack arrest markings on intergranular fracture surfaces. © 2011 The Minerals, Metals & Materials Society and ASM International. Source


Han L.,University of Warwick | Thornton M.,University of Warwick | Boomer D.,Innoval Technology | Shergold M.,Jaguar Land Rover
Journal of Materials Processing Technology | Year: 2011

AA5754 aluminium alloy was resistance spot welded (RSW) to produce 27 different joint stack-ups with differing process parameters and corresponding weld quality. Quasi-static joint strength was evaluated for three test geometries; lap-shear, coach-peel and cross-tension. The results derived from over 1000 samples demonstrate various fundamental relationships. For lap-shear strength, a strong relationship with weld nugget diameter was observed; whilst discrete strength levels were found for coach-peel test geometry, depending on the governing metal thickness of the parent sheet for the various stack-ups. For cross-tension strength; there is a relationship with nugget diameter; but data are sensitive to nugget periphery defects. These fundamental relationships provide a set of generalised design guidelines for RSW of aluminium that will have significant relevance to manufacturing communities. © 2010 Elsevier B.V. All rights reserved. Source


Holroyd N.J.H.,Case Western Reserve University | Scamans G.M.,Brunel University | Scamans G.M.,Innoval Technology
Corrosion | Year: 2016

Aluminum alloy usage in maritime environments has fluctuated over the past 125 years with localized corrosion or environment sensitive cracking during service repeatedly preventing their full commercial exploitation, despite a series of innovations. Following a historical overview, discussion will focus on aluminum-magnesium alloys, highlighting current corrosion-related issues (e.g., intergranular corrosion, environment sensitive cracking) and potential opportunities to eliminate these problems in future commercial alloys. © 2016, NACE International. Source


Grant
Agency: GTR | Branch: Innovate UK | Program: | Phase: Collaborative Research & Development | Award Amount: 340.04K | Year: 2012

Al-Si casting alloys have a wide range of applications in the automotive sector. These alloys contain high levels of silicon, which causes large grain sizes. Refining the grain size is crucial to achieve the superior performance castings. Grain refiners used for non-cast aluminium alloys are ineffective in cast aluminium due to the silicon levels. Brunel’s new grain refiner (BGR) provides a much needed solution to this problem. The BGR has the potential to transform practices in the Al-Si casting industry by enabling innovative, cheaper, and simpler casting to produce high performance cast structures. Delivering benefits to a wide range of casting techniques, it should enable castings with superior properties, thereby, allowing aluminium to replace some steel components in the automotive sector. The project aims at applying grain refiner to produce high performance Al-Si alloys cast components for automotive applications.


Grant
Agency: GTR | Branch: Innovate UK | Program: | Phase: Collaborative Research & Development | Award Amount: 262.00K | Year: 2012

The aim of the REPLICAL project is to develop a new roll to roll production process route using aluminium rollers for continuously manufacturing polymer film with similar anti-reflective properties to those of a moth-eye. Proof-of-concept for the nanoreplication process has been demonstrated. We intend to scale-up roller manufacture to a commercial scale and to demonstrate the manufacture of a range of moth-eye film products for the display and touch-screen markets. Roller manufacture requires special aluminium sheet as starting material and innovative surface finishing to produce rollers with the surface for direct polymer replication for anti-reflective properties. The innovative roll-to-roll nanoreplication process will lead to a step-change in UK competitiveness through a novel manufacturing route for a wide range of biomimetic functional polymer films.

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