Study guide
2.2 Non-Ferrous Metals and Alloys
ASNT NDT Level III Basic Examination Exam
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1 Introduction & Exam Overview
1.1 Current Exam Facts 1.2 Level III Role and Certification Path 1.3 Eligibility, Fees, Scheduling, and Retakes 1.4 Study Strategy and Exam-Day Approach
2 Chapter 2: Materials Fundamentals for NDT
2.1 Ferrous Metals and Iron-Carbon Phases 2.2 Non-Ferrous Metals and Alloys 2.3 Mechanical Properties and Crystal Structure
3 Chapter 3: Manufacturing Processes
3.1 Casting Processes and Cast Discontinuities 3.2 Forging, Rolling, and Forming 3.3 Extrusion, Drawing, and Machining 3.4 Heat Treatment Effects
4 Chapter 4: Welding and Joining Processes
4.1 Fusion Welding Processes 4.2 Weld Metal and HAZ Discontinuities 4.3 Brazing, Soldering, and Mechanical Joining
5 Chapter 5: Discontinuity Classification
5.1 Inherent Discontinuities 5.2 Processing Discontinuities 5.3 Service Discontinuities
6 Chapter 6: Specific Discontinuity Types
6.1 Cracks and Fracture Modes 6.2 Porosity, Inclusions, and Lack of Fusion 6.3 Laminations, Seams, Laps, and Undercut 6.4 Relevant vs Non-Relevant Indications
7 Chapter 7: NDT Method Selection and Inspection Planning
7.1 Method Selection Principles 7.2 Surface vs Volumetric Methods 7.3 Inspection Planning and Flaw Expectations
8 Chapter 8: Ultrasonic and Radiographic Testing
8.1 Ultrasonic Testing Principles and Applications 8.2 UT Limitations, Calibration, and Evaluation 8.3 Radiographic Testing Principles and Applications 8.4 RT Limitations, Image Quality, and Safety Basics
9 Chapter 9: Magnetic Particle, Liquid Penetrant, and Visual Testing
9.1 Magnetic Particle Testing 9.2 Liquid Penetrant Testing 9.3 Visual Testing
10 Chapter 10: Electromagnetic, Leak, Acoustic Emission, and Infrared Testing
10.1 Electromagnetic / Eddy Current Testing 10.2 Leak Testing 10.3 Acoustic Emission Testing 10.4 Thermal / Infrared Testing
11 Chapter 11: Specialty Methods and Method Comparison
11.1 Neutron Radiography 11.2 Magnetic Flux Leakage 11.3 Method Comparison and Supplemental Examinations
12 Chapter 12: SNT-TC-1A Recommended Practice
12.1 SNT-TC-1A Overview and Written Practice 12.2 SNT-TC-1A Training and Experience 12.3 SNT-TC-1A Examinations and Recertification
13 Chapter 13: CP-189 Standard Practice
13.1 CP-189 Overview and Scope 13.2 CP-189 Mandatory Requirements 13.3 SNT-TC-1A vs CP-189 Comparison
14 Chapter 14: CP-105 and NDT Training Programs
14.1 CP-105 Purpose and Topical Outlines 14.2 Developing and Approving NDT Training 14.3 OJT, Mentoring, and Instructor Oversight
15 Chapter 15: Building and Managing Certification Programs
15.1 Building Qualification and Certification Programs 15.2 Administering Examinations and Evaluating Competency 15.3 Program Audits and Managing Certifications
16 Chapter 16: Codes, Standards, Procedures, and Quality
16.1 Interpreting Codes, Standards, and Specifications 16.2 Developing and Approving NDT Procedures 16.3 Acceptance Criteria and Quality Control 16.4 External Audits and Inspection Documentation
2.2 Non-Ferrous Metals and Alloys
Key Takeaways Explain This Topic AI
Aluminum, copper, titanium, and nickel-base alloys are non-ferrous systems widely used where low density, conductivity, corrosion resistance, or high-temperature strength is required.
Work hardening strengthens metals by plastic deformation without changing composition; precipitation (age) hardening strengthens certain alloys by controlled heat treatment that forms fine precipitates.
Most common non-ferrous engineering alloys are non-magnetic, so conventional MT is not applicable; PT, ET, UT, RT, and VT become the primary surface and volumetric options.
High electrical conductivity (e.g., pure copper, pure aluminum) reduces eddy-current sensitivity depth and changes ET coil selection; density and atomic number strongly affect RT exposure and contrast.
Service corrosion—pitting, crevice attack, stress-corrosion cracking, and galvanic corrosion—creates the surface and near-surface flaws Level III procedures must anticipate on non-ferrous equipment.
Last updated: July 2026
Non-Ferrous Metals in the Level III Scope
Non-ferrous metals are metals and alloys whose primary base is not iron. On the Basic exam and in plant practice, the families that matter most are aluminum , copper and copper alloys , titanium , and nickel-base alloys , with magnesium and zinc appearing in lighter structural or coating roles. These materials show up in aerospace structures, heat exchangers, marine hardware, chemical process equipment, and high-temperature gas-path components.
A Level III does not need every temper designation memorized, but must answer three questions for any non-ferrous job:
How was strength developed (cold work, solid solution, precipitation, or combination)?
What physical properties constrain NDT (magnetism, conductivity, density, grain size, surface oxide)?
What discontinuities are likely from manufacturing and from service corrosion or fatigue?
- Major Alloy Families
- Aluminum alloys
Aluminum is low density (~2.7 g/cm³), corrosion resistant in many atmospheres due to a passive oxide, and highly workable. Pure aluminum is soft; engineering strength comes from alloying and temper:
Non-heat-treatable alloys (e.g., many 3xxx, 5xxx series): strengthened mainly by solid solution and cold work (strain hardening) .
Heat-treatable alloys (e.g., many 2xxx, 6xxx, 7xxx series): strengthened by solution heat treatment + quenching + aging ( precipitation hardening ).
Typical product forms: plate, sheet, extrusions, forgings, castings, weldments. Typical discontinuities: porosity and shrinkage in castings; lack of fusion and porosity in welds (especially if oxide is not cleaned); stringers/inclusions from rolling; fatigue cracks at fastener holes and stress raisers; stress-corrosion cracking in susceptible tempers and environments (classic concern in some high-strength 7xxx products).
NDT notes: Non-magnetic → no conventional MT . PT for surface cracks and porosity openings. ET widely used on thin sheet, tubing, and aerospace structure (conductivity also used for heat-treat verification). UT for thicker plate and forgings; coarse cast structure may limit UT. RT effective for volume defects in castings and welds; low atomic number means lower absorption than steel—technique charts differ.
Copper and copper alloys
Copper offers excellent electrical and thermal conductivity and good corrosion resistance in many waters. Alloys include brasses (Cu-Zn), bronzes (e.g., Cu-Sn, aluminum bronze), and copper-nickels.
Strengthening: cold work is common; some alloys age harden. Product forms: tube, pipe, plate, castings, electrical bus. Discontinuities: porosity in castings; seams and inclusions in wrought product; dezincification and stress-corrosion cracking (ammonia environments on some brasses); erosion-corrosion in high-velocity water; fatigue in vibrating heat-exchanger tubes.
NDT notes: Non-magnetic. Very high electrical conductivity of pure copper reduces eddy-current penetration (small skin depth at a given frequency)—ET is still used on tubing but coil design, frequency, and fill-factor matter. RT works well; copper’s higher density/atomic number vs aluminum increases absorption. UT is routine on thicker sections; PT for surface-breaking flaws.
Titanium alloys
Titanium combines moderate density, high strength-to-weight, and outstanding corrosion resistance (especially to chloride environments when the passive film is intact). Aerospace airframes, landing-gear components, medical implants, and chemical equipment are common homes.
Crystal structure note: pure titanium is HCP (α) at room temperature and becomes BCC (β) at high temperature; alloys are α, near-α, α+β, or β types. Limited slip systems in α make deformation more directional and raise sensitivity to texture.
Discontinuities: hard-alpha inclusions and high-density inclusions (historic aerospace concern); porosity in castings; welding contamination from oxygen/nitrogen/hydrogen (embrittlement); fatigue cracks; crevice corrosion or hydriding under specific process conditions.
NDT notes: Non-magnetic. UT and ET are workhorses for aerospace forms; PT for surface; RT for castings and welds. Surface cleanliness and oxide/scale can affect PT and ET; Level III procedures must control surface condition.
Nickel and nickel-base alloys
Nickel alloys (including many high-temperature superalloys and corrosion-resistant alloys such as various Ni-Cr-Mo grades) serve where heat, oxidation, or aggressive chemistry defeats steel and aluminum. Strengthening mechanisms include solid solution, cold work, and precipitation hardening (e.g., γ′ in some superalloys).
Discontinuities: solidification segregation and freckles in large castings/ingots; hot tears; weld solidification cracking or heat-affected liquation cracking in susceptible alloys; creep voids and thermal-fatigue cracks in service; carburization or sulfidation damage in process environments.
NDT notes: Generally non-magnetic (some alloys can show slight response depending on composition and cold work). PT, UT, RT, ET dominate. High-temperature parts often need careful surface prep after scale removal; acceptance criteria may be driven by creep-fatigue design, not just fabrication codes.
- Strengthening Mechanisms Level III Must Distinguish
- Work hardening (strain hardening)
Work hardening raises strength and hardness by plastic deformation that multiplies dislocations. No composition change is required. Effects:
- Strength ↑, ductility ↓, residual stress often ↑
- Can induce preferred orientation ( texture ) and anisotropy
In some austenitic stainless and other alloys, severe cold work can form strain-induced martensite and create local magnetism —an exam-relevant exception to “austenitic = always non-magnetic”
Overworked surfaces may show orange peel , cracking, or reduced fatigue life
Annealing after cold work restores ductility by recovery, recrystallization, and grain growth—and resets NDT baselines (conductivity for ET hardness/temper checks on aluminum is a classic example).
Precipitation hardening (age hardening)
Precipitation hardening applies to alloys with temperature-dependent solid solubility (many Al, Ni, Cu-Be, some stainless grades):
Solution treat — dissolve alloying elements into a single solid solution.
Quench — trap a supersaturated solid solution.
Age (naturally or artificially) — fine precipitates form and impede dislocations.
Underaging / peak aging / overaging change strength and toughness. For NDT, improper heat treatment may not create a “crack,” but it changes conductivity, hardness, and residual stress , which can be monitored with ET conductivity or hardness methods and which alter fatigue and SCC susceptibility.
Physical Properties That Drive RT, UT, and ET
- Property Aluminum (approx.) Copper (approx.) Titanium (approx.) Carbon steel (ref.) NDT implication
- Density Low (~2.7 g/cm³) High (~8.9) Moderate (~4.5) ~7.8 RT exposure time and contrast; UT velocity tables
Electrical conductivity High (pure Al higher than alloys) Very high Relatively low Moderate ET skin depth and sensitivity
Magnetic behavior Non-magnetic Non-magnetic Non-magnetic Ferromagnetic MT not applicable to common non-ferrous
Acoustic behavior Alloy/temper dependent Good UT medium Alloy/phase dependent Grain-sensitive Velocity and attenuation calibration must match material
RT: Higher density and higher atomic number absorb more radiation. Aluminum may need softer techniques or longer exposures than steel for equivalent thickness contrast; copper and nickel alloys absorb more strongly.
UT: Use correct velocity and expect different attenuation . Coarse cast aluminum or titanium structures can scatter like coarse steel castings.
ET: Conductivity sets standard depth of penetration. High-conductivity copper needs different frequency/coil strategy than lower-conductivity titanium alloys. Lift-off and edge effects still apply.
Non-Magnetic Reality: MT Is Off the Table
For the large majority of aluminum, copper, titanium, and nickel components, conventional magnetic particle testing is not applicable because the materials cannot be usefully magnetized. Level III procedure review should reject MT callouts on non-magnetic non-ferrous parts and substitute:
- PT for surface-breaking flaws (watch chemical compatibility with aluminum and titanium)
- ET for surface/near-surface cracks and thinning in conductive parts
- UT for internal volume and thickness
- RT for volumetric manufacturing flaws
- VT always as the first and continuous method
- Corrosion Behaviors That Create Service Flaws
Non-ferrous equipment often fails by corrosion-assisted mechanisms rather than simple overload:
Pitting and crevice corrosion — localized attack under deposits, gaskets, or stagnant zones; pits act as fatigue starters; PT/VT/ET detect open pits; deep subsurface pits may need UT thickness or RT.
Stress-corrosion cracking (SCC) — tensile stress + specific environment + susceptible alloy/temper (e.g., some brasses in ammonia, some Al alloys in moist chloride-bearing conditions). Cracks are tight and branched; surface methods and UT crack sizing strategies matter.
Galvanic corrosion — dissimilar metal couples (Al fastened to steel, Cu in contact with Al) accelerate attack of the anodic member; look for wall loss at joints.
Erosion-corrosion / fretting — high-velocity fluids or vibration remove protective films; common in copper-alloy heat-exchanger tubes.
Hot corrosion / oxidation — nickel alloys in turbines; scale and subsurface attack complicate surface NDT until cleaning is controlled.
Level III takeaway: When writing a technique for non-ferrous service inspection, start from alloy + environment + stress state , then pick methods that can find the expected crack morphology and wall-loss pattern , not from a steel-based default checklist.