Hot-compression tests were conducted in a high-energy synchrotron x-ray beam to study in situ and in real time microstructural changes in the bulk of a β-solidifying titanium aluminide alloy. The occupancy and spottiness of the diffraction rings have been evaluated in order to access grain growth and refinement, orientation relationships, subgrain formation, dynamic recovery, and dynamic recrystallization, as well as phase transformations. This method has been applied to an alloy consisting of two coexisting phases at high temperature and it was found that the bcc β-phase recrystallizes dynamically, much faster than the hcp α-phase, which deforms predominantly through crystallographic slip underpinned by a dynamic recovery process with only a small component of dynamic recrystallization. The two phases deform to a very large extent independently from each other. The rapid recrystallization dynamics of the β-phase combined with the easy and isotropic slip characteristics of the bcc structure explain the excellent deformation behavior of the material, while the presence of two phases effectively suppresses grain growth.

The properties of metallurgical coke are critical to the performance of the blast furnace for iron making. While extensive work has gone into understanding the relationship between the properties of coke and its behaviour in the blast furnace, the heterogeneous nature of coke makes understanding these relationships difficult. Herein we report the use of a laboratory produced coke analogue to examine the effects of minerals on the reactivity behaviour of coke in a pseudo-CRI test. The effects of a range of minerals on the reactivity of the coke analogue are demonstrated and the effects of binary combinations of silicon and iron bearing minerals are examined.

A new experimental technique defined as concentric solidification has been developed to improve in-situ observations of solidification and high temperature phase transformations using laser scanning confocal microscopy (LSCM). The technique consists of applying a radial thermal gradient across a 10 mm diameter sample such that the maximum temperature is focused in the centre of the specimen. Careful control over the sample thickness, heating rate and peak temperature results in the formation of a liquid pool in the centre of the specimen. Surface tension balance between solid, liquid, gas and crucible result in minimal meniscus formation on the liquid pool, leading to a greatly enhanced in-situ observations. Examples of the range of observations possible as well as unique observations of segregation related phenomena are presented.

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Theoretical and experimental investigation of thermal and oxidation behaviours Theoretical and experimental investigation of thermal and oxidation behaviours of a high speed steel work roll during hot rolling of a high speed steel work roll during hot rolling

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Intermetallic titanium aluminides (Ti-Al) are a class of novel, light-weight materials with attractive mechanical properties at high temperatures, making them desirable for applications in the automotive and aerospace industries. [1,2] Because of the small ''deformation window'' in thermomechanical parameter space hot-working of g-TiAl alloys is a complex and difficult task and, therefore, isothermal forming processes are favored. In order to increase the deformation window novel Nb and Mo containing g-TiAl based alloys, so-called TNM TM alloys, were developed, which solidify via the atomic-species-disordered b-phase space and also exhibit an adjustable b-phase volume fraction. [3,4] The disordered b-phase which exhibits a bcc lattice provides a sufficient number of independent slip systems. It therefore improves the deformability at elevated temperatures. For detailed information on TNM alloys, e.g., development strategy, processing, microstructure, and mechanical properties the reader is referred to recent papers. [4][5][6][7] Due to high volume fractions of disordered b-phase at temperatures above the a-transus temperature TNM alloys can be hot-die forged under near conventional conditions, which means that conventional forging equipment with minor and inexpensive modifications can be used. [4,8] At service temperature (T < 750 8C), however, the b-phase shows an ordered B2-structure, designated b 0 . At room temperature, three major phases are present in the investigated TNM alloy: g-TiAl revealing an ordered tetragonal L1 0 -structure, a 2 -Ti 3 Al forming an ordered hexagonal DO 19 -structure and b with an ordered cubic B2-structure. Note, minor phases, such as borides, play also important metallurgical roles, but will not be considered in this study. At elevated temperatures, both a 2 and b 0 show disordering, i.e., a 2 ! a, a disordered hcpstructure and b 0 ! b, a disordered bcc-structure. Volume fractions and arrangement of these phases in the microstructure are decisive for hot-working and determine the mechanical properties in service. In situ studies provide real-time information on the phase composition and evolution from the bulk of a material, thus delivering important information for defining hot-working parameters and for designing effective heat treatments in multi-phase materials. Neutron diffraction performed on TiAl alloy is sensitive to the atomic order of these phases. In the present study, we have investigated the ordering/disordering of the b 0 /b and a 2 /a phases as well as the dissolution/formation of the g-phase atIn recent times, novel titanium aluminides containing the bcc b-phase at high temperatures are being developed for improved hot-working capabilities, however, predictions of the phase diagrams are merely uncertain. Here we present in-situ neutron studies, which are particularly sensitive to the atomic disorder in the ordered phases. Complementary laser scanning confocal microscopy is employed for in-situ microstructural investigations.932

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