Lecture

Hexagonal Lattice in Mg Alloys

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In course

MSE-422: Advanced metallurgy

This course covers the metallurgy, processing and properties of modern high-performance metals and alloys (e.g. advanced steels, Ni-base, Ti-base, High Entropy Alloys etc.). In addition, the principles of computational alloy design as well as approaches fo ...

Description

This lecture discusses the hexagonal lattice structure in magnesium and titanium, focusing on the c/a ratio, slip systems, and dislocation motion. It also covers the deformation behavior of polycrystalline magnesium and its alloys at different temperatures, emphasizing the role of critical resolved sheer stress and diffusion-controlled mechanisms. Furthermore, it explores strengthening mechanisms in materials, such as grain boundary strengthening, solid solution strengthening, and precipitation hardening. The lecture delves into the concept of long-range order in intermetallic structural alloys, the lattice structure of NiAl, and the brittleness of these alloys at room temperature. It concludes with a failure case analysis of undercarriage trunnion failure and a broken wire cutter, highlighting fracture mechanisms, stress analysis, metallographic evaluations, and conclusions drawn from the investigations.

Instructor

Christian Leinenbach

Official source

Ontological neighbourhood

Chemical engineering

Materials science: Alloys, Deformation of materials

Chemistry

Organic chemistry: Organometallic chemistry

Related concepts (32)

Grain boundary strengthening

In materials science, grain-boundary strengthening (or Hall–Petch strengthening) is a method of strengthening materials by changing their average crystallite (grain) size. It is based on the observation that grain boundaries are insurmountable borders for dislocations and that the number of dislocations within a grain has an effect on how stress builds up in the adjacent grain, which will eventually activate dislocation sources and thus enabling deformation in the neighbouring grain as well.

Hardening (metallurgy)

Hardening is a metallurgical metalworking process used to increase the hardness of a metal. The hardness of a metal is directly proportional to the uniaxial yield stress at the location of the imposed strain. A harder metal will have a higher resistance to plastic deformation than a less hard metal. The five hardening processes are: The Hall–Petch method, or grain boundary strengthening, is to obtain small grains. Smaller grains increases the likelihood of dislocations running into grain boundaries after shorter distances, which are very strong dislocation barriers.

Tin

Tin is a chemical element with the symbol Sn () and atomic number 50. A silvery-coloured metal, tin is soft enough to be cut with little force, and a bar of tin can be bent by hand with little effort. When bent, the so-called "tin cry" can be heard as a result of twinning in tin crystals; this trait is shared by indium, cadmium, zinc, and mercury in its solid state. Pure tin after solidifying presents a mirror-like appearance similar to most metals. In most tin alloys (e.g. pewter) the metal solidifies with a dull grey colour.

Silicon

Silicon is a chemical element with the symbol Si and atomic number 14. It is a hard, brittle crystalline solid with a blue-grey metallic luster, and is a tetravalent metalloid and semiconductor. It is a member of group 14 in the periodic table: carbon is above it; and germanium, tin, lead, and flerovium are below it. It is relatively unreactive. Because of its high chemical affinity for oxygen, it was not until 1823 that Jöns Jakob Berzelius was first able to prepare it and characterize it in pure form.

Inconel

Inconel is a nickel-chromium-based superalloy often utilized in extreme environments where components are subjected to high temperature, pressure or mechanical loads. Inconel alloys are oxidation- and corrosion-resistant, when heated, Inconel forms a thick, stable, passivating oxide layer protecting the surface from further attack. Inconel retains strength over a wide temperature range, attractive for high-temperature applications where aluminum and steel would succumb to creep as a result of thermally-induced crystal vacancies.

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Precipitation Hardening in Alloys

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Mechanical Properties & Strengthening Mechanisms

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Explores dislocations, grain boundaries, and hardening mechanisms in metals through thermal treatments and recrystallization.

The Superalloys: Alloy Design and Properties

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Related concepts (32)

Grain boundary strengthening

Hardening (metallurgy)

Tin

Silicon

Inconel