Lecture 1: Materials Flashcards
What is a material in the context of manufacturing?
A material consists of elementary particles, which directly influence what is possible in production. Materials can range from metals and plastics to composites and more.
What are the two types of connection between atoms?
Atomic Structure: Atoms of the same type cluster together, forming structures like metals, which are made of many small crystals oriented randomly.
Molecules: Atoms connect to form molecules, as seen in plastics where many polymer chains are interwoven.
How are the properties of metals determined?
Metal properties are determined by:
Types of Atoms - Different metals have different atomic structures.
Connection Type - How atoms bond together, affecting the crystal structure.
What are the common types of crystal structures found in metals?
Body-centered cubic (bcc): Atoms find the most energetically optimal spot, allowing easier deformation. Consist of the atom in the middle and at the corners
Face-centered cubic (fcc): Consists of atoms in the middle of each plane and at the corners of each plabe. Found in metals like iron under 914 degrees Celsius.
Hexagonal close-packed (hcp): Difficult to deform due to hexagonal arrangement, found in metals like titanium and zinc.
How does the cooling process affect the crystal structure of metals?
Fast Cooling: Leads to smaller crystals, resulting in a material that is harder and more difficult to deform.
Slow Cooling: Allows for larger crystals to form, which can cause segregation based on melting points of different atoms, affecting material uniformity.
What is anisotropic behavior in metals?
Anisotropy in metals refers to the variation in material properties depending on the direction of the measurement. This occurs when metals are subjected to cold deformation and do not recrystallize, causing grains to deform and create an irregular structure with a preferred direction.
What are the different types of plastics and their key properties?
Thermoplastics: Become viscous when heated; can be reshaped.
Elastomers: Behave like a cross between thermosetting and thermoplastics; examples include rubbers.
Thermosetting Plastics: Disintegrate when heated; cannot be reshaped.
Co-polymers and Poly-blends: Consist of macromolecules from different monomers or types, providing diverse physical properties.
Plastics = polymers + a lot of additions. Additions:
i.cheaper filler (polymers are expensive)
ii. improves mechanical properties – add glass/metal/etc. to make material harder
iii. improves process ability – change the viscous temperature of the material
iv. the more we mix plastics ➔ the more additives we add ➔ the more difficult it will become for recycle
