Preparation Considerations
Cutting
Characteristics:
- Many non-ferrous metals, especially aluminum and other softer alloys, are relatively ductile and deform more easily during sectioning
- Soft matrices can smear, burr, or drag at the cut edge more readily than many ferrous materials
- Preparation-induced damage can penetrate more deeply than expected if the cut is too aggressive
- Buehler notes that wet cutting with ample coolant is important for aluminum to reduce overheating and mechanical strain
More Attention:
- Coolant flow directly into the cutting zone
- Blade selection and cutting severity for soft or ductile alloys
- Burr formation, edge quality, and local deformation after sectioning
- Support and clamping stability for thin or delicate sections
- Whether the cut surface is cleanly separated rather than mechanically smeared
Avoid:
- Heavy burr formation at the cut edge
- Dragged or folded metal at the surface
- Thermal or mechanical disturbance that extends too deeply into the specimen
- A cut condition that increases the amount of material that must be removed during grinding
- Loss of near-surface fidelity before the specimen enters the next step
Mounting
Characteristics:
- Many non-ferrous specimens include soft edges, thin sections, or surface features that are easily altered during preparation
- Ductile materials can lose edge definition more easily if support is insufficient
- Sample geometry often includes thin walls, irregular shapes, or feature-specific cross-sections
- Buehler recommends castable mounting for aluminum samples that are thin or deform easily
More Attention:
- Uniform edge support around the specimen
- Specimen orientation relative to the final observation plane
- Shrinkage behavior and adhesion of the mounting medium
- Whether mounting heat or pressure may distort soft material features
- Stability of the specimen in the mount before grinding begins
Avoid:
- Poor edge retention during later preparation
- Shrinkage gaps around soft or thin sections
- Specimen movement within the mount
- Distortion introduced by excessive heat, pressure, or insufficient support
- Loss of the true observation plane before the specimen reaches polishing
Grinding
Characteristics:
- Soft and ductile non-ferrous metals can develop deeper deformation during grinding than harder materials
- Surface smearing and dragging are common risks, particularly in purer or softer grades
- Embedded abrasive particles are a recognized artifact in aluminum preparation
- Buehler advises frequent replacement of SiC papers and close abrasive-step progression for aluminum alloys
More Attention:
- Whether the previous damage layer has actually been removed
- Condition and sharpness of the grinding surface
- Signs of smearing, dragged metal, or embedded abrasive particles
- Pressure, time, and step progression between abrasive sizes
- Whether the specimen is being cut cleanly by the abrasive rather than simply flattened visually
Avoid:
- False flatness that hides residual deformation
- Embedded abrasive particles in the surface
- Dragged metal and smeared surface layers
- Retention of sectioning damage into later steps
- A grinding result that appears acceptable but is not yet metallographically clean
Polishing
Characteristics:
- Soft non-ferrous matrices scratch easily and can appear bright before they are fully free of preparation damage
- Residual smearing, fine deformation, and particle embedding may remain hidden beneath a visually smooth surface
- Differences in phase hardness can also make local relief more noticeable in some non-ferrous alloys
- Buehler notes that soft aluminum and pure aluminum are especially susceptible to deformation and scratches during finishing
More Attention:
- Whether fine polishing is removing damage or only improving appearance
- Residual smearing beneath a bright surface
- Fine scratches and embedded particles that remain after earlier steps
- Condition of soft phases, edges, and near-surface regions
- Whether the final surface is suitable for reliable microstructural interpretation rather than only visual smoothness
Avoid:
- A bright but still mechanically disturbed surface
- Residual fine scratches or embedded abrasives
- Relief that obscures true structural relationships
- Distorted edge and near-surface information
- A polished finish that looks clean but does not accurately represent the specimen
