Mr. Rogers' IB Design Technology Objectives
metals - ferrous (iron or iron alloys) or nonferrous
  1. Draw and describe a metallic bond.

  1. Explain why metals are very good electrical and thermal conductors. (It's the movement of free electrons.)

  • one or more electrons in the outer shell are free to move

  1. Describe the physical  structure of pure or alloyed metals.

  • crystalline--highly organized arrangements of atoms

  • grain structure--small crystalline regions

  1. Explain how grain size can be controlled and modified by the rate of cooling of the molten metal, or by heat treatment after solidification.

  • Rapid cooling or quenching: Small grain size, high tensile strength, high hardness

  • Slow cooling: Large grain size, greater malleability

  • Selective cooling: directional properties in the structure

  • Reheating or tempering: material diffuses between neighboring grains changing the grain structure