The Structure-Properties -Processing Relation

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1 MME131: Lecture 4 The Structure-Properties -Processing Relation A. K. M. B. Rashid Professor, Department of MME BUET, Dhaka Today s Topics Study of structure of materials Understand the structure-properties-processing-performance tetrahedron Connect how microstructure relates to properties Look at the effect of processing on microstructure and properties Reference Books : 1. Callister. Materials Science and Engineering: An Introduction, Ch Shackelford. Introduction to Materials Science for Engineers, Ch01. Lec 04, Page 1/18

2 What are Structures? Structure defines the internal conditions of materials and relates to how a material is put together. It has many dimensions. 1. Electronic or Subatomic Structure Electronic structure of individual atoms (electrons and nucleus) that defines interaction among atoms (interatomic bonding) 2. Atomic Structure Arrangement of atoms or molecules in materials (material with the same atom can have different properties; e.g. two forms of carbon: graphite and diamond). When arranged in 3D space, these are called crystal structures. 3. Microscopic Structure Groups of atoms that are agglomerated together to form small grains (gives different properties; e.g., strength, optical properties etc.) 4. Macroscopic Structure Structural elements that may be viewed with the naked eye Example: Steel hammer head Macrostructure (or, shape) of the hammer Lec 04, Page 2/18

3 Ferrite grains Pearlite grains Grain boundary 0.38 wt.% carbon steel hammer head microstructure Crystal structure of the hammer head Iron has a body-centred cubic (BCC) crystal structure at room temperature Lec 04, Page 3/18

4 26P 30N The 2 electrons in the outer shell are not tightly held. This allows iron to form metallic bonds with longrange crystal structure, and to conduct electricity Electronic structure of iron that make the hammer Terminology and Unit millimeter = 1,000-1 meter = 10-3 m = 1 mm micrometer = 1,000,000-1 meter = 10-6 m = 1 µm nanometer = 1,000,000,000-1 meter = 10-9 m = 1 nm Angstrom = 10,000,000,000-1 meter = m = 1 Å 1 Micrometer is Two Wavelengths of Green Light Long Elongated bumps that make up the data track on CD are ~ 0.5 µm wide, minimum 0.83 µm long, and 125 nm high A hair is ~ 50 micrometers in diameter Lec 04, Page 4/18

ch/microcosm Leaf 10 centimeter source: Glenn

5 Understanding Size Flower bed 1 meter source: Glenn Fishbine CERN Leaf 10 centimeter source: Glenn Fishbine CERN Lec 04, Page 5/18

ch/microcosm Composite Eye of Fly 100-1000

6 Fly 1 centimeter source: Glenn Fishbine CERN Composite Eye of Fly micrometer source: Glenn Fishbine CERN Lec 04, Page 6/18

ch/microcosm Antenna between Eyes 1 micrometer source:

7 Individual Eye of Fly 10 micrometer source: Glenn Fishbine CERN Antenna between Eyes 1 micrometer source: Glenn Fishbine CERN Lec 04, Page 7/18

ch/microcosm Individual Gene in the DNA 1 nanometer

8 DNA of Fly 10 nanometer source: Glenn Fishbine CERN Individual Gene in the DNA 1 nanometer source: Glenn Fishbine CERN Lec 04, Page 8/18

9 Logarithmic scale of structures size, m Atomic structure Crystal structure X-ray & neutron diffraction Microstructure Macrostructure Transmission electron microscopy Scanning electron microscopy Optical microscopy What are Properties? Properties are the material traits (distinguishing features) indicating the ways the material responds to the environment and external forces. Virtually all important properties of solid materials may be grouped into six different categories: Mechanical properties response to mechanical forces (elastic modulus, strength, etc.) Electrical properties response electrical fields (conductivity, dielectric constant, etc.) Magnetic properties response magnetic fields (magnetization, permeability, etc.) Thermal properties are related to transmission of heat (heat capacity, thermal conductivity, etc.) Optical properties relate to the absorption, transmission and scattering of electromagnetic or light radiation (refraction index, reflectivity, etc.) Chemical stability indicates reactivity with the environment (corrosion resistance, etc.) Lec 04, Page 9/18

make-up of a material. Synthesis is the process by which materials are made from naturally occurring or other chemicals.

10 What are Processing? In addition to structure and properties, two other important components are involved in the science and engineering of materials namely, processing and performance Composition means the chemical make-up of a material. Synthesis is the process by which materials are made from naturally occurring or other chemicals. Processing means different ways of shaping materials into useful components or changing their properties Performance means the accomplishment relative to stated goals or objectives The Structures Property Processing Performance Tetrahedron Engineered structures are not black boxes. They are made from raw materials which have a processed internal structure. This internal structure affects the properties of the material. Performance Structure Properties Processing The materials tetrahedron Lec 04, Page 10/18

Understanding of how materials behave like they do, and why they differ in properties was only possible with the atomistic understanding of matter allowed by quantum mechanics, which first explained

11 Understanding of how materials behave like they do, and why they differ in properties was only possible with the atomistic understanding of matter allowed by quantum mechanics, which first explained atoms and then solids. The combination of physics, chemistry, and the focus on the relationship between the properties of a material and its microstructure is the domain of Materials Science. The development of this science allowed designing materials and provided a knowledge base for the engineering applications (Materials Engineering) Brooks/Cole Publishing / Thomson Learning Lec 04, Page 11/18

tetrahedron to sheet steels for automotive chassis.

12 2003 Brooks/Cole Publishing / Thomson Learning Application of the tetrahedron to ceramic superconductors 2003 Brooks/Cole Publishing / Thomson Learning Application of the tetrahedron to sheet steels for automotive chassis. Lec 04, Page 12/18

Example To understand the properties of engineering materials, it is necessary

crystalline structure non-crystalline or, amorphous structure glass fibres in

13 2003 Brooks/Cole Publishing / Thomson Learning Application of the tetrahedron to semiconducting polymers for microelectronics From structures to properties: Example To understand the properties of engineering materials, it is necessary to understand their structure on the atomic and/or microscopic scale crystalline structure non-crystalline or, amorphous structure glass fibres in GFRP Atomic-level structure (x10 7 ) Microscopic-level structure (x10 3 ) Lec 04, Page 13/18

Close-packed net It is easier for crystal lattice deformation to occur in the direction that is close

14 Case study 1: Atomic-scale architecture Ductility of aluminium and magnesium Broken tensile test pieces of Al and Mg Crystal structure of Al (Cubic) and Mg (hexagonal) Principles of Atomic Packing Square net Close-packed net It is easier for crystal lattice deformation to occur in the direction that is close packed. The number and direction of close-packed planes vary according to packing sequence of crystal. Lec 04, Page 14/18

HCP Cell FCC Cell Close-packed Close-packed Total Close-packed System Planes Directions (plane x direction) FCC 4 3 4 x

architecture Making of transparent ceramics High temperature sodium vapour lamp Polycrystalline alumina containing

15 HCP Cell FCC Cell Close-packed Close-packed Total Close-packed System Planes Directions (plane x direction) FCC x 3 = 12 HCP x 3 = 3 Since FCC has more close-packed system, it deforms more easily Case study 2: Microscopic-scale architecture Making of transparent ceramics High temperature sodium vapour lamp Polycrystalline alumina containing porosity 15 lumens/w Polycrystalline alumina plus 0.1 wt.% magnesia with near pore-free structure 100 lumens/w Lec 04, Page 15/18

Hardness (BHN) Structure - properties relation of plain

structure of steel structure controls the properties of

30 mm (c) (b) 4 mm 30 mm (d) 100 0.01 0.

16 Hardness (BHN) Structure - properties relation of plain carbon steels composition (carbon content) controls the structure of steel structure controls the properties of steel Properties depend on structure (a) 30 mm (c) (b) 4 mm 30 mm (d) Cooling Rate (ºC/s) 30 mm Processing can change structure! Lec 04, Page 16/18

From processing to structure: Example Rolling of Steel During rolling and extrusion, the grains of material are deformed and become elongated along the rolling direction, which imparts directional

17 From processing to structure: Example Rolling of Steel During rolling and extrusion, the grains of material are deformed and become elongated along the rolling direction, which imparts directional properties to the material. low UTS low YS high ductility round grains high UTS high YS low ductility elongated grains During casting, the liquid metal cools from three directions and grains of uniform shape are created, which imparts non-directional or isotropic properties to the material. Structure determines properties but processing controls structure! From processing to property: Example Lec 04, Page 17/18

18 Next Class MME131: Lecture 5 Atomic Bonding and Materials Properties Lec 04, Page 18/18

Materials Sciences. Dr.-Ing. Norbert Hort norbert.hort@gkss.de. International Masters Programme in Biomedical Engineering

Materials Sciences. Dr.-Ing. Norbert Hort norbert.hort@gkss.de. International Masters Programme in Biomedical Engineering Materials Sciences International Masters Programme in Biomedical Engineering Magnesium Innovations Center (MagIC) GKSS Forschungszentrum Geesthacht GmbH Dr.-Ing. Norbert Hort norbert.hort@gkss.de Contents