Note to Readers[edit | edit source]

Consider the following:

CET(Columnar to equiaxed transition)[edit | edit source]

Background[edit | edit source]


  • TBD - additive manufacturing or a materials science welding journal

From Wikipedia: [1]

Why CET[edit | edit source]

The columnar to equiaxed transition is critical for preventing crack growth along the columnar dendrites from the root towards the center of the solidifying metal. Equiaxed grains terminate cracks, limiting the total crack length and improve the mechanical properties of the material.

Factors of CET[edit | edit source]

The general factors which influence the CET are

  • Thermal Gradient
    • Cooling rate
    • Melt size
  • Solidification Velocity
    • Nucleation rate
  • Alloy composition
    • Grain Refiner
      • Constitutional Supercooling

Impact of WAAM on CET[edit | edit source]

WAAM(Wire arc additive manufacturing)

  • Multi-layer process disrupts the long range order of the solidifying microstructure through re-melt fraction
  • Reduces the section size/melt size of the object for any given moment
  • turbulent and convectional flow from the welding process results in a homogeneous microstructure element distribution
  • Rapid solidification allows a "as solutionized" like microstructure preventing the need for a costly heat treatment.

Running Notes and Ideas[edit | edit source]

General ideas and notes regarding CET and its impact on solidifying materials

  • Minimize the length of the columnar region (which acts as max crack length)
  • Minimize the thermal gradient(to allow nucleation ahead of the columnar front) by improving resolution
  • Increase the solidification rate to transition to equiaxed structure sooner.

Metrics of CET[edit | edit source]

  • Dendrite size (SDAS for solidification velocity)
  • Hardness / conductivity (for solutionized state)
  • Length % of columnar region (for transition time)
  • Length(distance) of columnar region (for max potential crack length)

Literature Review of CET[edit | edit source]

  • Areas of Focus:
    • Microstructure impact
    • Hot tear reduction

Microstructure Focus[edit | edit source]

Microstructure of Rapidly Solidified Materials[edit | edit source]

Jones, H., 1984. Microstructure of rapidly solidified materials. Materials Science and Engineering, Solidification Microstructure: 30 Years after Constitutional Supercooling 65, 145–156.

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