Deposits of clastic carbonate-dominated (calciclastic) sedimentary slope systems in the rock record have been identified mostly as linearly-consistent carbonate apron deposits, even though most ancient clastic carbonate slope deposits fit the submarine fan systems better. Calciclastic submarine fans are consequently rarely described and are poorly understood. Subsequently, very little is known especially in mud-dominated calciclastic submarine fan systems. Presented in this study are a sedimentological core and petrographic characterisation of samples from eleven boreholes from the Lower Carboniferous of Bowland Basin (Northwest England) that reveals a >250 m thick calciturbidite complex deposited in a calciclastic submarine fan setting. Seven facies are recognised from core and thin section characterisation and are grouped into three carbonate turbidite sequences. They include: 1) Calciturbidites, comprising mostly of highto low-density, wavy-laminated bioclast-rich facies; 2) low-density densite mudstones which are characterised by planar laminated and unlaminated muddominated facies; and 3) Calcidebrites which are muddy or hyper-concentrated debrisflow deposits occurring as poorly-sorted, chaotic, mud-supported floatstones. These

Phd by thesis

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Introduction To Electrodynamics

Semisolid metal (SSM) processingis a relatively new technology for metal forming. Different from the conventional metal forming technologies which use either solid metals (solid state processing) or liquid metals (casting) as starting materials, SSM processing deals with semisolid slurries, in which non-dendritic solid particles are dispersed in a liquid matrix. Semisolid metal slurries exhibit distinctive rheological characteristics: the steady state behaviour is pseudoplastic (or shear thinning), while the transient state behaviour is thixotropic. All the currently available technologies for SSM processing have been developed based on those unique rheological properties, which in turn originate from their non-dendritic microstructures. Year 2001 marks the 30th anniversary of the concept of SSM processing. Today, SSM processing has established itself as a scientifically sound and commercially viable technology for production of metallic components with high integrity, improved mechanical properti...

Semisolid metal processing

Semisolid metal processing is a relatively new method for forming alloys in the semisolid condition to near net shaped products. It relies on the behaviour of semisolid slurries in which the solid exists in the form of spheroidal particles: if left undisturbed such slurries are stiff and may be handled, but flow like liquids on being sheared. Slugs of semisolid alloy may therefore be injected into a die (thixocasting) or shaped between closed dies (thixoforging) to produce components near-to-shape with good surface finish, free from porosity, and possessing fine uniform microstructures, which may be heat treated to give superior mechanical properties. The rheology of non-dendritic alloy slurries and the recent ideas which have been proposed to account for their pseudoplastic and thixotropic behaviour are considered. This is followed by a description of the technologies available for producing non-dendritic structures and the processes for subsequently shaping the semisolid alloy. Finally, some ind...

Modelling the semisolid processing of metallic alloys

Commercial thixoforming is generally based on conventional aluminum-based casting alloys such as A356 and A357. However, these alloys do not give such high mechanical properties as the alloys that are conventionally wrought such as 2000, 6000 and 7000 series or the high-strength aluminium casting alloys such as 201. In this paper, 201, 2014, 6082, 7075, 7010 and ‘modified’ versions of 2014 (3.87 wt.% Cu, 0.6 wt.% Mg, 0.14 wt.% Si), 6082 (1.29 wt.% Si, 1.21 wt.% Mg) and 7075 (6.01 wt.% Zn, 3.99 wt.% Mg, 2.06 wt.% Cu, 0.12 wt.% Si) were thixoformed. The recrystallisation and partial (RAP) melting route and the cooling slope (CS) casting route were used to obtain the semi-solid feedstock for thixoforming. Microstructural evolution during partial melting was studied at temperatures where the amounts of liquid were comparable for the various alloys. Tensile mechanical properties of thixoformed parts in the T6 condition were determined and compared with those of conventionally wrought alloys and thixoformed high performance aluminium alloys from the literature. The tensile properties of the thixoformed alloy 201 show a significant improvement over permanent mould casting and the tensile properties of the thixoformed 2014, with an optimised heat treatment schedule, were close to those of forged 2014 but with lower elongation to fracture. Good elongation to fracture (19.6%) was obtained for thixoformed ‘modified’ 2014 in the T6 condition, with a yield strength of 270 MPa and a tensile strength of 408 MPa. This yield strength is significantly short of the target wrought 2014 value and the tensile strength is a little short. The elongations to fracture (24.4 and 12.3%) are satisfactory for alloy 6082 and ‘modified’ 6082 but yield strength and tensile strength need to be increased to achieve the wrought 6082 target. The tensile properties for 7075 thixoformed from starting material produced by the recrystallisation and partial melting route are a little better than those of 7075 thixoformed from starting material produced on the cooling slope. Both routes give values close to the wrought target 7075. The yield strength and tensile strength for ‘modified’ 7075 and 7010 are quite close to the wrought target.

Microstructural evolution and tensile mechanical properties of thixoformed high performance aluminium alloys

Commercially extruded 7075 alloy (extrusion ratio of 16:1) has been used as a feedstock for thixoforming in order to investigate thixoformability of a high performance aluminium alloy. The microstructure in the semi-solid state consists of fine spheroidal solid grains surrounded by liquid. The results of thixoforming with one step, two-step and three-step induction heating regimes are presented. Typical defects in poorly thixoformed material (e.g. liquid segregation, impedance of flow by unrecrystallised grains and porosity) are shown alongside successfully thixoformed material (thixoforming temperature of between 615 and 618 °C with a three-step induction heating regime). The highest yield strength and elongation obtained for material thixoformed into a simple graphite die and heat treated to the T6 condition is 478 MPa and 6.9% elongation. For thixoforming at 615 °C into a tool steel die heated to 250 °C, the highest yield strength and elongation obtained are 474 MPa and 4.7% (ram velocity 2000 mm/s). These values (particularly for strength) are approaching those of 7075 in the wrought heat treated condition (505 MPa and 11% elongation).

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Thixoforming 7075 aluminium alloys

Simple rheocasting processes

Des pieces peuvent etre obtenues dans un etat proche de leur forme finale en une seule operation par le procede d'elaboration semi-solide. C'est une technique qui combine les avantages du moulage et du forgeage

Plato Kapranos

Papers

Microstructural evolution and tensile mechanical properties of thixoformed high performance aluminium alloys

Thixoforming 7075 aluminium alloys

Simple rheocasting processes

Semi-solid processing of alloys

Thixoforming of an automotive part in A390 hypereutectic Al-Si alloy