Metallurgical Analysis

Etching Selection

Grain Size Measurement

1. ASTM E112 Methods

   • Comparison method: Match to standard charts
   • Planimetric method: Count grains in known area
   • Intercept method: Count grain boundary intersections

2. Calculation

   • Apply magnification correction
   • Use minimum 5 fields for statistical validity
   • Report ASTM grain size number with standard deviation

3. Special Cases

   • Duplex structures: Report both phases separately
   • Elongated grains: Measure aspect ratio
   • Prior austenite: Use specific etchants (picric acid based)

Inclusion Rating (ASTM E45)

1. Method Selection

   • Method A: Worst field rating
   • Method D: Quantitative measurement
   • Specify inclusion type (A, B, C, D sulfides, oxides)

2. Reporting

   • Include severity (thin, heavy) and length
   • Note distribution (random, stringer, cluster)
   • Compare to specification limits

Process Integration

• MS-002: Electron Microscopy Characterization
• MS-017: Root Cause Failure Analysis

Input Schema

{
  "sample_id": "string",
  "alloy_system": "steel|aluminum|titanium|copper|nickel",
  "alloy_grade": "string",
  "analysis_type": "grain_size|phase_fraction|inclusion|weld_eval",
  "magnification": "number",
  "etchant_used": "string"
}

Output Schema

{
  "sample_id": "string",
  "grain_size": {
    "astm_number": "number",
    "average_diameter": "number (microns)",
    "standard_deviation": "number",
    "method": "string"
  },
  "phase_fractions": [
    {
      "phase": "string",
      "fraction": "number (percent)",
      "morphology": "string"
    }
  ],
  "inclusion_rating": {
    "method": "string",
    "type_a": "number",
    "type_b": "number",
    "type_c": "number",
    "type_d": "number"
  },
  "observations": "string"
}

Best Practices

1. Document complete preparation procedure for reproducibility
2. Use consistent magnification within a comparative study
3. Apply appropriate etching time - under-etched is better than over-etched
4. Verify grain boundaries are fully revealed before measurement
5. Use image analysis software for quantitative phase measurements
6. Include representative micrographs in reports

Integration Points

• Connects with Electron Microscopy for high-resolution analysis
• Feeds into Failure Analysis for metallographic investigation
• Supports Mechanical Testing for structure-property correlation
• Integrates with Heat Treatment Optimization for process development