Seminar by Dmytro Orlov, new Professor in Materials Engineering at LTH
You are cordially invited to attend a seminar on "Magnesium: Competitive Advantage, Key Drivers and Recent Achievements in Alloy Development"
Time: Wednesday May 6th, 15:15-16:30 hrs
Place: Lecture hall M:B in the M-building on the LTH campus
Magnesium (Mg) is a material with hexagonal close-packed (HCP) lattice, parameters of which are very attractive for basic studies. It is also a lightest structural metal, which possesses density of 1.74 g cm^-3 – just a quarter of that in steels or two-thirds in aluminium. This makes it extremely attractive for light-weight mobility including automotive, aerospace and electronic device sectors, corresponding energy or fuel conservation as well as hydrogen storage. Moreover, magnesium is also friendly to environment and absolutely biocompatible by itself, so as the products of its degradation in bio-environments. Nevertheless, in real world, the use of Mg as a pure metal is often restricted by inadequate performance, and thus alloying is utilised in combination with thermo-mechanical treatment for meeting demands. Among these, fatigue and bio-corrosion are the hottest performance issues to be tailored for mobility and bio-medical sectors, respectively.
Phenomena relevant to fatigue in HCP metals, including Mg, are very different from those in steels and other metals with cubic lattice due to significantly lower number of available slip systems and an extended tendency to twinning. Moreover, the latter has polar nature leading to very anisotropic response to mechanical loading, which keeps even in random-textured material, as demonstrate recent studies. Alloying and grain refinement can significantly affects such behaviour, and thus improve the fatigue performance of Mg.
The problem of Mg bio-corrosion is relevant to excessively high degradation rate in body fluids leading to overly rapid hydrogen gas release, which damages tissues. The mitigation of such a problem is complicated by very limited solubility of alloying elements and a large mismatch in the lattice parameters between Mg base metal and the degradation products leading to delaminating and re-exposure of the matrix. Nevertheless, appropriate precipitation of intemetallic phases can mitigate the bio-degradation rate.
Recent views on these issues and our achievements in their control will be discussed in the lecture, with a particular emphasis at Mg alloy design involving deformation processing. The improvements in performance are explained based on such microstructure characteristics as texture, grain size and precipitate state. These characteristics were revealed by optical profilometry, back-scattered electron imaging and diffraction analysis in SEM, high-resolution TEM, and synchrotron radiation. The activities of deformation mechanisms were assessed by in-situ monitoring of acoustic emission (AE) during mechanical loading using unique in-house designed system and algorithms for the analysis of AE signal.