The quantitative determination of products of isothermal desintegration of austenite

With the help of a constitution diagram Fe – Fe3C, a diagram TTT and vertical structural diagram of the authors´ own construction it is determined that the relative amount of products in steel occurs in any temperature of isothermal disintegration of austenite. Making use of camouflage it is enabled to set bouth structural and phasic composition of alloy at the same time. In case of use of appropriate animating software (e.c. Macromedia Flash) it is possible to practise this quantification on steel of any chemical composition.

Microstructures of Laser Processed Fe-Cr Surface Alloys

In recent years, the effects of chromium on the transformation characteristics of pure iron and the structures produced thereby have been extensively studied as a function of cooling rate. In this paper, we present TEM observations made on specimens of Fe-10% Cr and Fe-20% Cr alloys produced through laser surface alloying process with an estimated cooling rate of 8.8 x 104°C/sec. These two chromium levels were selected in order to study their phase transformation characteristics which are dissimilar in the two cases as predicted by the constitution diagram. Pure iron (C<0.01%, Si<0.01%, Mn<0.01%, S=0.003%, P=0.008%) was electrodeposited with chromium to the thicknesses of 40 and 70μm and then vacuum degassed at 400°F to remove the hydrogen formed during electroplating. Laser surface alloying of chromium into the iron substrate was then performed employing a continuous wave CO2 laser operated at an incident power of 1200 watts. The laser beam, defocussed to a spot diameter of 0.25mm, scanned the material surface at a rate of 30mm/sec, (70 ipm).

On the martensitic transformation in f. c. c. manganese alloys. I. Measurements

Lattice dynamical properties of antiferromagnetic f. c. c. Mn 83 Ni 11 C 6 and Mn 85 Ni 9 C 6 have been studied by means of ultrasonics and neutron scattering. The two alloys illustrate how, with increase of manganese content across this region of the constitution diagram, severe elastic anomalies develop in these materials. In particular, for these concentrations the magnitude of the elastic stiffness constant C 11 begins to fall off drastically towards the lower temperatures, passing below C 44 ; in Mn 85 Ni 9 C 6 it reduces with reducing temperature to such an extent that a cubic-to-tetragonal martensitic transformation is induced. At the transformation temperature C 11 has a minimum, rising again thereafter. A detailed study has been made of one specimen of Mn 85 Ni 9 C 6 that showed a nearly second-order structure transition. In this sample, 1/2( C 11 — C 12 ) softens linearly with temperature, reaching 0.27 x 10 10 N m -2 ( x 10 11 dyn cm -2 ) at the transformation temperature T m = 174 ± 2 K, where Zener’s anisotropy parameter attains the value 36. Other elastic properties likewise prove to be extremely unusual, with longitudinal sound propagating more slowly than transverse sound along the cube axis directions. Phonon energy measurements, made to an accuracy of about 40 μeV, show however that as a function of wavevector appreciable phonon softening is restricted to a small central region of the Brillouin zone within about a tenth of a reciprocal lattice unit of the origin. The anomalous inter-atomic forces responsible are markedly non-central, and it is argued they are a consequence of an enhanced electron-phonon interaction arising because the manganese moment is unstable. The applicability of molecular field theory to the transition is well confirmed, the critical index γ of the order parameter above T m being obtained as 1.03 ± 0.07.