Introduction | Structure of Metals and Alloys | Crystalline materials


Crystalline Materials:

  • A crystalline material is one in which the atoms are situated in a repeating (or) periodic array over large atomic distances.



Non Crystalline Materials:

  • Materials that do not crystallize are called non-crystalline (or) Amorphous materials

Space Lattice | Structure of Metals and Alloys

  • Lattice is the regular geometrical arrangement of points in crystal space.



  • The atoms arrange themselves in distinct pattern in space is called a Space Lattice.
  • Atoms in crystalline materials are arranged in a regular 3 – Dimensional repeating pattern known as Lattice Structure.
  • They are divided by network of lines in to equal volumes, the points of intersection are known as Lattice Points.

Unit Cell | Structure of Metals and Alloys


  • It is the smallest portion of the lattice which repeated in all directions.
  • 3D visualization of 14 Space Lattices are known as Bravai’s Space Lattice.
  • If a unit cell contains lattice points only at it’s corners, then it is called Primitive Unit Cell (or) Simple Unit Cell.
  • Three edge length x,y, & z and three interaxial angles α, β, & γ are termed as Lattice Parameters.

Crystal System For The Structure of Metals and Alloys

  • It is a scheme by which crystal structures are classified according to unit cell geometry.

Types of Crystal Systems:

  • Cubic
  • Tetragonal
  • Hexagonal
  • Orthorhombic
  • Rhombohedral
  • Monoclinic
  • Triclinic

Crystal Systems


Simple Crystal Structure:

Body Centered Cubic Structure (BCC)

  • Unit cell contains 2 atoms
  • Lattice Constant a= 4r / √3, where r is atomic radius
  • Atomic packing factor APF = 0.68
  • Metals are Vanadium, Molybdenum, Titanium, Tungsten




Face Centered Cubic (FCC)

  • Unit cell contains 4 atoms
  • Lattice Constant a= 4r / √2, where r is atomic radius
  • Atomic packing factor APF = 0.72
  • FCC structures can be plastic deformed at severe rates
  • Metals are Copper, Aluminum, Phosphorous, Nickel, Cobalt etc


01-Fcc-Structure-Face-Center-Cubic-Unit-CellHexagonal Closed Packed Structure (HCP)

  • Unit cell contains 3 atoms
  • Axial ratio c/a, where ‘c’ is Distance between base planes, ‘a’ is Width of Hexagon
  • Axial Ratio varies from 1.58 for Beryllium to 1.88 for Cadmium (Therefore  a=2.9787, c=5.617)
  • Atomic packing factor APF = 0.74
  • Metals are Zinc, Cadmium, Beryllium, Magnesium etc





Crystallographic Planes and Directions

The Layers of atoms in the planes along which atoms are arranged is known as “Atomic” (or) “Crystallographic planes”.

Miller Indices:

Miller Indices is a system of notation that denotes the orientation of the faces of a crystal and the planes and directions of atoms within that crystal.

Miller Indices for Planes:

1. The (110) surface



Intercepts :   a , a , ∞

Fractional intercepts :   1 , 1 , ∞

Miller Indices :   (110)


2. The (111) surface



Intercepts :   a , a , a

Fractional intercepts :   1 , 1 , 1

Miller Indices :   (111)

The (100), (110) and (111) surfaces considered above are the so-called low index surfaces of a cubic crystal system.


3. The (210) surface



Intercepts :   ½ a , a , ∞

Fractional intercepts :   ½ , 1 , ∞

Miller Indices :   (210)



  • Mechanical Objective Questions | Mechanical Objective Type
    Mechanical Objective Questions Mechanical Objective Questions  1. Which of the following variable controls the physical properties of a perfect gas? a. Pressure b. Temperature c. Volume d. Atomic mass e. All of the above Answer: All of the above   2. If heat be exchanged in reversible manner, which of the following property of the...
  • The 14 Principles Of The Deming Management Philosophy: An In-Depth Guide To Success
    The mission of the Deming Management Philosophy is to improve the performance, quality, and competitiveness of an organization by applying the Deming Management System.
  • A Guide To Total Quality Control (TQC) : 8 Steps
    Total Quality ControlContents1 Total Quality Control1.1 History of Total Quality Control1.2 Definition of Total Quality Control1.2.1 ‘‘Control’’ represents a tool with four steps :1.3 The quality of any product is influenced by a number of factors during the manufacturing process:1.4 Total Quality Control has eight characteristics1.4.1 1. Customer Focused1.4.2 2. Employees Involved1.4.3 3. Process-driven1.4.4 4....
  • Statistical Quality Control | SQC
    A Statistical Quality control system performs inspection, testing and analysis to conclude whether the quality of each product is as per laid quality standard or not.
  • Interview Questions On Fluid Mechanics | Mechanical Engineering Basics
    Interview Questions On Fluid MechanicsContents1 Interview Questions On Fluid Mechanics1.0.1 1. How Cavitation can be eliminated in a Pump? | Interview Questions on Fluid Mechanics1.0.2 2. Which pump is more efficient Centrifugal pump or Reciprocating pump? | Interview Questions on Fluid Mechanics1.0.3 3. Why Centrifugal Pump is not called as a Positive Displacement Type of...

Introduction | Structure …

by magnaparthi