What is Metallurgical Analysis?
Metallurgical analysis is a general description of the study of metal alloys chemical, physical and mechanical properties. At the core of this description is the microscopic observation of prepared specimens for features (micro and macro) of specified interest. These features can include, but not be limited to: grain size, inclusion content, phase content and distribution, segregation, porosity or voiding, intermetallics, heat treatments, and surface or near surface treatments. In addition, this description encompasses failure analysis and the comprehensive study and presentation of data and information gathered during the investigation.
Metallurgical analysis finds its roots in early science when it was understood that the properties of extracted metals from minerals could be altered with cold and hot working, heat treatments, and aging. Of course during the industrial revolution, these properties had to be understood with more sophistication to lead to finished goods with consistent and targeted properties for the application. For ferrous metallurgy this modern birth was during the early steel making era. At this time, many universities began to supplement their chemistry and mining curriculums with modern metallurgy. Today, many formal dedicated metallurgy programs have morphed into materials sciences programs with the advent of additional materials used in manufacturing, such as plastics, ceramics, composites, and other advanced structures.
When Is Metallurgical Analysis Utilized?
In this laboratory, although we have also adapted to many other materials sciences, the concentration is still on metallurgical analysis in support of industries such as automotive, transportation, chemical engineering, medical devices, forging, heat treating, casting, furniture, circuit boards and components, powdered metals, and appliances. Metallurgical analysis is utilized when someone asks, “How hard is this?”, “What is the chemical makeup?”, “Does this meet the manufacturing specification for this part?” and so forth. The process can be as simple as a hardness indentation, or as complex as a full failure analysis where many metallurgical analysis techniques are employed.
Logistically we can break down the fundamental metallurgical analysis techniques with the referenced testing methods as follows:
Mechanical and Physical Properties:
- Yield Strength, Tensile Strength, Elongation, Modulus of Elasticity, Reduction of Area– ASTM E8, ASTM A370, SAE J995, JIS Z2201, JISZ2241
- Plastic Strain ratio (r-value) – ASTM E517
- Work Hardening Exponent (n-value) – ASTM E646
- Brinell Hardness – ASTM E10
- Rockwell Hardness – ASTM E18
- Impact Testing (Charpy v-notch) – ASTM E23
- Vickers Hardness – ASTM E72
- Microhardness (Knoop and Vickers) – ASTM E384
Metallic Surface Treatments:
- Coating Thickness – ASTM B487
- Coating Weights – ASTM A90, A428
- Surface analysis by Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray Spectroscopy (EDS) – ASTM B748, E986
- Metallurgical Preparation – ASTM E3
- Case Depth – SAE J423
- Cast Iron Rating – ASTM A427, SAE J158, J434
- Depth of Decarburization – ASTM E1077, SAE J419
- Grain Size – E112
- Inclusion Content – ASTM E45
- Macroetch – ASTM A561, A604, E340, E381
- Microetch – ASTM E407
- Glow Discharge (GD-OES) and Arc Spark Spectroscopy (OES) – ASTM E415
- Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP-AES) – ASTM E1613
What Sample Size is Required to Perform Metallurgical Analysis?
The required sample sizes are varied and are typically described in detail in the referenced methods. Most techniques, however, allow for testing where sample sizes are minimal, and will require some degree of laboratory extraction (such as from parts) or laboratory preparation (including machining to prepare a specimen for analysis. If in doubt for your required sample sizes and submittal requirements, just ask the laboratory.
Which Metallurgical Materials can be Tested?
The laboratory employs expertise in testing of metallurgical materials of both the ferrous and non-ferrous nature. Ferrous materials or alloys include carbon steel, low alloy steel, stainless steel, tool steel, cast iron, ductile iron, and gray iron. Non-ferrous materials or alloys include aluminum, magnesium, copper (pure, brass, and bronzes), zinc, nickel, titanium, and tin.