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Steels Processing Group Facilities and Equipment

WMG research into iron and steel manufacturing involves both developing novel approaches and new technologies, as well as modifying existing technologies and processes. We are developing facilities related to our strategic research to enable flexibility in raw materials, casting technologies for near-net-shape strips and coating and thermo-mechanical processing. Our group has also established a number of key research collaborations which enable sharing of equipment with other state-of-the-art centres. Our suite of equipment includes:

Confocal Scanning Laser Microscope

The High Temperature Confocal Scanning Laser Microscope (HT-CSLM) is used to image metallurgical reactions and transformations at temperatures up to 1700oC. Using a scanning laser combined with confocal optics, the CSLM is able to image the sample's surface, in spite of the glow, and detect clear changes in contrast. The confocal nature detects only signals from the focal plane while decreasing the intensity of signals from other planes. The laser further increases the signal / noise ratio. This makes the CSLM ideal for imaging surfaces at high temperature.
The instrument has recently been upgraded to include an in-situ compression/tension stage allowing for the observation of phenomena such as recrystallization, deformation due to inclusion and measurement of material expansion due to temperature changes. With the previous high temperature stage being used for a range of investigations such as exploring peritectic solidification, slag-metal emulsification, oxide fluxing and isothermal solidification due to chemistry changes.
The equipment works on the premise of a gold-plated elliptical furnace which serves to reflect the IR-radiation from a halogen bulb (in 1 focal point) to the sample (in the second focal point). The sample is held in a crucible of suitable material on a platinum ring, to which a control thermocouple is attached to. This temperature reading is sent to an external temperature controller, which uses the reading to control the amperage (and therefore the intensity) of the halogen lamp.
The video output from the HT-CSLM in sent to a computer by way of analog-digital converter and is recorded by a software package. The temperature controller is connected to a computer by serial port, and so can have two-way communication with the program. Examples of HT-CSLM images and movies are shown here. Due to the surface imaging and high temperatures, the equipment is highly sensitive to atmospheric purity, as such pre-getters and filters are used to achieve up to parts per-trillion levels of oxygen when required.
The instrument has also been developed to offer unique capabilities such as: in-situ powder addition, thermal imaging of temperature gradients, high resolution cross imaging for sessile drop testing and gas humidification for moisture experimentation.

Confocal

 

Videos:

Solidification of peritectic steel:

Austenite - ferrite transformation of HSLA steel at 700oc

Austenite – bainite & martensite
transformation

Scanning Electron Microscopy with Electron Back Scattered Diffraction and Focused Ion Beam

High resolution Field Emission Gun Scanning Electron Microscope (FEGSEM) is suitable for the analysis of microstructure of materials including their chemical composition. By applying the Electron Back Scattered Diffraction (EBSD) detector, texture and crystallographic orientation of each grain can be evaluated. Incorporating an additional Focused Ion Beam (FIB) source with SEM can be applied to either prepare in-situ 3D maps of microstructural features such as micro-porosity, cracking or 3D texture maps. FIB lift-out methods can be used to cut thin sections for further analysis using Transmission Electron Microscopy (TEM).

The image to the right shows a SEM FIB image of in-plane section of Zn coated boron steel sample with milled out trenches before lift-out; M= martensite; a1 and a2= grains of αFe(Zn) separated by grain boundary (also see TEM below).

SEM FIB image

SEM FIB image
(also see below)

Transmission Electron Microscopy (TEM)

High resolution TEM and Scanning TEM (STEM/TEM) is available through an active collaboration between WMG and the Physics Department (Materials and Analytical Sciences). The modern High Resolution STEM microscope (JEOL 2100) is equipped, not only with conventional bright filed TEM imaging, but also with a high-angle Annular Dark Field (HAADF) to complement chemical analysis by Energy Dispersive Spectroscopy (EDS) with information on atomic contrast. HAADF images are very easy to interpret and are essential during study of precipitation behaviour or the role of intermetallic particles during thermo-mechanical processing of steels and Al and Mg alloys. In addition, conventional JEOL 2000FX TEM microscope is available to carry out low resolution imaging and EDS analysis with magnification between x5,000 and x750,000.

The image to the right shows a TEM image of in-plane section of Zn coated boron steel sample with milled out trenches before lift-out; M= martensite; a1 and a2= grains of αFe(Zn) separated by grain boundary (also see SEM FIB above).

The graph to the right also illustrates corresponding Zn distribution when comparing TEM EDS and less accurate SEM EDS data.

TEM image

TEM image of the same location
SEM and TEM comparison

EDS Comparison - SEM and TEM