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

A review of dynamic recrystallization phenomena in metallic materials

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

Failure of metals I : brittle and ductile fracture

The Avrami kinetics of dynamic recrystallization

The dynamic recrystallization (DRX) behavior of Nb and Nb–Ti microalloyed steels has been investigated. It has been observed that the initial austenite grain size, the amount of microalloying elements in solid solution, and the deformation conditions (temperature and strain rate), affect dynamic recrystallization kinetics. To characterize the dynamic recrystallization behavior of the microalloyed austenite, continuous torsion tests were carried out after reheating the specimens at different temperatures between 1000 and 1420 °C, leading to a wide range of initial grain sizes, from 16 to 805 μm. It has been observed that decreasing the values of the Zener–Hollomon parameter and the initial grain size, promotes dynamic recrystallization. Microalloying elements in solid solution produce a retardation of dynamic recrystallization, resulting in higher values of the characteristic critical, e c , and peak, e p , strains. A corrective factor has been applied to quantify the retardation produced by the increase in the amount of Nb and Ti dissolved as the reheating temperature increases. In this manner, it has been possible to propose a unique relationship to predict the e p peak strain for both steels.

Dynamic recrystallization behavior covering a wide austenite grain size range in Nb and Nb–Ti microalloyed steels

Deformation dilatometry has been used to simulate controlled hot rolling followed by cooling of a Nb–V low carbon steel, looking for conditions corresponding to wide austenite grain size distributions prior to transformation. Recrystallization and non-recrystallization deformation schedules were applied, followed by controlled cooling at rates from 0.1 °C/s to about 200 °C/s, and the corresponding continuous cooling transformation (CCT) diagrams were constructed. The resultant microstructures ranged from polygonal ferrite (PF) and pearlite (P) at slow cooling rates to bainitic ferrite (BF) accompanied by martensite (M) for fast cooling rates. Plastic deformation of the parent austenite accelerated both ferrite and bainite transformations, displacing the CCT curve to higher temperatures and shorter times. However, it was found that the accelerating effect of strain on bainite transformation weakened as the cooling rate diminished and the polygonal ferrite formation was enhanced. Moreover, it was found that plastic deformation had different effects on the refinement of the microstructure, depending on the cooling rate. An analysis of the microstructural heterogeneities that can impair toughness behavior has been done.

Effect of austenite microstructure and cooling rate on transformation characteristics in a low carbon Nb–V microalloyed steel

Semi-solid processing of novel MMCs based on hypereutectic aluminium-silicon alloys

The wear resistance of nine eutectic and hypereutectic Al–Si alloys with various compositions and processing routes was studied. Testing was conducted using a pin-on-disc configuration and two different testing speeds. At lower disc speed, the influence of the composition and alloy processing was very strong and a severe wear transition was observed for the alloys with low fractions of primary silicon particles. At higher disc speed, wear of all the alloys but one was very low. The high wear alloy had a high silicon content and a very large primary silicon size; the accelerated wear was caused by cracking and fracture of the large silicon particles upon impact with the abrasive disc material at the higher speed.

Jose M. Rodriguez-Ibabe

Papers

Dynamic recrystallization behavior covering a wide austenite grain size range in Nb and Nb–Ti microalloyed steels

Effect of austenite microstructure and cooling rate on transformation characteristics in a low carbon Nb–V microalloyed steel

Semi-solid processing of novel MMCs based on hypereutectic aluminium-silicon alloys

Wear behaviour of eutectic and hypereutectic Al-Si-Cu-Mg casting alloys tested against a composite brake pad

Relationship between the austenite recrystallized fraction and the softening measured from the interrupted torsion test technique