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.
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.
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.
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.
Agency: Cordis | Branch: FP7 | Program: CP-IP | Phase: NMP-2009-3.2-1 | Award Amount: 8.31M | Year: 2010
The project concept is to combine nanoreactor technology with multisite solid catalyst design to achieve a safer, cleaner and intensified chemical production. The project ideas are the following: (i) From micro- to nano-reactors. Actual microreactor have channels of micrometric size. We will develop a new concept based on the use of nanometric size channels. (ii) Vectorial pathway for multisite catalytic reactions. A limit in cascade (or domino) reactions is that there is no possibility to control the sequence of reactions of transformation of a reactant in a multisite catalyst. The concept of vectorial pathway for multisite catalytic reactions is based on the idea of an ordered sequence of catalytic sites along the axial direction of the channels of a membrane, in order to control the sequence of transformation. (iii) Dynamic nanoreactor. The concept of dynamic nanoreactor is based on the transient generation of toxic reactants inside the nanoreactor and the immediate conversion, in order to eliminate the storage of these reactants (which is minimized, but not eliminated in on-site or on-demand approaches). The project concept is that the implementation of innovative and safer pathways for sustainable chemical production requires making a step forward in the development of catalyst-reactor design along the lines indicated above. The project applies above ideas to three reactions of synthesis of large-volume chemicals which are relevant example of innovative pathways for sustainable chemical production: (1) direct synthesis of H2O2, (2) PO synthesis with in-situ generated H2O2 and (3) solvent-free synthesis of DPC with in-situ transient generation of phosgene. The consortium has a clear industrial leadership, with sixth major companies and two SMEs, and four academic partners, plus the participation of the durable institution of the NoE IDECAT.