French fancies from the Renaissance and early Baroque

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National saints

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Italian Baroque opera

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Centres and peripheries of 15th-century music

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The wedding of the century, Munich 1568

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Composition effects on the fcc-hcp martensitic transformation and on the magnetic ordering of the fcc structure in Fe-Mn-Cr alloys

Publication date: 15 February 2017
Source:Materials & Design, Volume 116
Author(s): L.M. Guerrero, P. La Roca, F. Malamud, A. Baruj, M. Sade
This paper presents an experimental study on the fcc/hcp martensitic transformation temperatures (MTTs) and Néel temperatures (TN) of the fcc phase of Fe-Mn-Cr alloys. A wide range of chemical compositions (13.7<Mn<27.5wt.% and 0<Cr<12.4wt.%) has been studied. X-ray diffraction measurements were conducted in order to confirm that the martensitic transformation takes place between an fcc structure and the hcp martensite. Transition temperatures were measured by means of electrical resistivity and dilatometry. All transition temperatures tend to decrease with the increment in Cr content while the addition of Mn decreases the MTTs and increases TN. These different effects and the stabilization effect of the antiferromagnetic ordering on the fcc austenite result in different MTTs behaviors depending on whether the martensitic transition occurs from a magnetically ordered austenite or not. For these later cases, a phenomenological model of MTTs is presented that could be of use for alloys design.

Graphical abstract

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Exceptional thermal strain reduction by a tilting pillar architecture: Suspended Ge layers on Si (001)

Publication date: 15 February 2017
Source:Materials & Design, Volume 116
Author(s): Anna Marzegalli, Andrea Cortinovis, Francesco Basso Basset, Emiliano Bonera, Fabio Pezzoli, Andrea Scaccabarozzi, Fabio Isa, Giovanni Isella, Peter Zaumseil, Giovanni Capellini, Thomas Schroeder, Leo Miglio
In this paper we present the exceptional thermal strain release provided by micrometric Si pillar arrays to Ge epitaxial patches suspended on them, for different pillar aspect ratios and patch sizes. By combining 3D and 2D Finite Element Method simulations, low-energy plasma-enhanced chemical vapor deposition on patterned Si substrates, μ-Raman, μ-photoluminescence and XRD measurements, we provide a quantitative and consistent picture of this effect with the patch sizes. Strain relaxation up to 85% of the value for the corresponding planar films can be obtained for a squared patch 100μm in size. Finally, the enhanced thermal strain relaxation is analytically explained in terms of the Si pillar lateral tilting, critically dependent on the pillar aspect ratio, very similarly to the well-known case of a deflected beam. Our results are transferable to any material deposited, or wafer bonded at high temperature, on any patterned substrate: wafer bowing can be controlled by micrometric patterned features well within the present capabilities of deep reactive ion etching.

Graphical abstract

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