Class 1 materials are characterized by their low hardness (typically below 150 HV) and high ductility. These materials present unique challenges in metallographic preparation due to their tendency to deform, smear, and embed abrasive particles. Proper preparation is crucial for revealing true microstructural features and preventing artifacts.
Soft materials are prone to mechanical deformation during cutting and grinding, leading to distorted microstructures.
Surface smearing can obscure grain boundaries and second-phase particles.
Abrasive particles can become embedded in the soft surface, requiring careful cleaning between steps.
Special care is needed to preserve oxide inclusions and prevent their removal during preparation.
Use low-speed abrasive cutting with minimal force. Consider using a coolant to prevent heat generation and subsequent deformation.
Compression mounting is preferred for most applications. Use low-pressure mounting for extremely soft materials to prevent deformation.
Begin with coarse SiC paper (180-240 grit) and progress through finer grits. Use minimal force and frequent cleaning between steps.
Use diamond suspensions on appropriate polishing cloths. Final polish with colloidal silica or alumina to remove any remaining deformation.
Check for absence of deformation under polarized light
Verify grain boundaries are clearly visible
Ensure second-phase particles are not smeared
Confirm oxide inclusions are preserved