Shear Relief

I’m very happy that my paper was accepted for publication in Metallurgical and Materials Transactions A. It took a long time from performing the experiment to presenting the results, mainly because I needed to repeat the analysis which was something I wasn’t able to make time for until I had to submit the thesis.

Surface relief caused by shear transformation of bainite

In the paper atomic force microscopy is used to measure the shear component of extremely thin plates of bainitic ferrite in superbainite. The shear component is surprisingly large compared to the value we expected of 0.23–0.28 based on previous experiments carried out after transformation at higher temperatures (such as the results by Swallow and Bhadeshia).

It seems like the higher strain may help to explain why the bainitic ferrite plates are so thin and slender. It would now be really interesting to test if that is true or not, which is something I couldn’t really do by looking at the TEM and SEM images I have already.

More details on my web-page at Mathew Peet| Papers| Surface Relief Due to Bainite Transformation at 200°C

Article is currently available electronically by using DOI

Ferrite crystal structure in cmd format for jmol


<?xml version="1.0"?>
<molecule xmlns="http://www.xml-cml.org/schema">
<crystal>
<scalar title="a">2.882</scalar>
<scalar title="b">2.882</scalar>
<scalar title="c">2.882</scalar>
<scalar title="alpha">90.00</scalar>
<scalar title="beta">90.00</scalar>
<scalar title="gamma">90.00</scalar>
</crystal>
<atomArray>
<atom id="Fe1" xFract="0.0" yFract="0.0" zFract="0.0" elementType="Fe"/>
<atom id="Fe2" xFract="0.5" yFract="0.5" zFract="0.5" elementType="Fe"/>
</atomArray>
</molecule>


After viewing cmlexplained.
Jmol is a an open-source Java viewer for chemical structures

Density of Iron Carbide (Fe3C)

There are 4 molecules of Fe₃C per unit cell. The cell is orthorombic, typical lattice parameters at room temperature are given below from Mehl etal, Trans AIMME, 1933.

Mass
——-

m = mass of 1 mole of unit cells
= 12 x Fe_RAM + 4 x C_RAM
= 12 x 55.845 + 4 x 12.011 = 670.14 + 48.044
= 718.184 g/mol

Fe₃C unit cell is 718.184 g/mol

Volume
——-
v = volume of 1 mole of unit cells
= A_V x a x b x c
= 6.0221415 × 10²³ x 4.518 x 5.069 x 6.736 x 10^-30
= 9.2901×10^-5 m³

Density
——-
d = density
= m/v
= 0.71814 kg / 9.2901 x 10^-5 m³
= 7730.14 kg/m³

View FCC Austenite in three dimensions

Channel 4 seem to be showing some 3d programs on t.v. the consequence is you can get 3d glasses for free in sainsburys, and you can use them with the Jmol sorfware to view molecular models in three dimensions.

2 FCC unit cells (click image to enlarge)

Using GSAS and EXPGUI in debian

EXPGUI is a graphical interface for the GSAS software, allowing structural refinement using the Reitveld technique.

EXPGUI/GSAS can be downloaded in binary form from http://www.ncnr.nist.gov/programs/crystallography/software/downloads.html

You need to install tcl/tk and also blt all of which can be found in debian package repositories. (Or whatever for your system!)

in debian:
apt-get tk8.4 blt

tcl/tk is the scripting language used to write EXPGUI.
failing to install blt will result in the error “Error — Unable to load the BLT package; cannot run liveplot”.