Testing And Assay Guide For Titanium Alloy Materials

The performance of titanium alloy materials directly affects the service life and safety of products. Standardized and full-process testing and assay must be conducted to ensure that the composition, microstructure, performance and defects all comply with specifications.

 

 

 

1. Core Objectives

• Determine whether the material grade and composition meet the standards
• Verify that the mechanical properties meet the design requirements
• Inspect internal and surface defects to eliminate early failure
• Confirm the qualification of metallographic structure and heat treatment state
• Support quality traceability and third-party certification (CMA/CNAS)

 

2. Applicable Objects

Ingots, bars, plates, pipes, forgings, castings and precision parts of titanium and titanium alloys;

 

3. General Standard Basis

International: ASTM B265/B348, AMS 4928, ISO 5832 (Medical use)

 

 

1. Mandatory Test Elements

• Major alloying elements: Ti, Al, V, Mo, Nb, Zr, Sn, etc.
• Key impurities: Fe, Si, C, Cl
• Hazardous gaseous elements: O, N, H

 

2. Common Testing Methods

• Optical Emission Spectrometry : Rapid judgment upon incoming inspection, simultaneous multi-element analysis, accuracy of ±0.005%

ICP-OES/ICP-MS: High-precision quantitative analysis, suitable for trace and ultra-trace element analysis

• Inert gas fusion method: Special for O/N/H detection, with a detection limit as low as ppm level, controlling the risk of hydrogen embrittlement
• XRF: Non-destructive and rapid screening, suitable for random surface inspection of finished products

 

3. Key Limits (Taking Gr5 as an Example)

Al: 5.5–6.8%; V: 3.5–4.5%

Fe ≤ 0.30%; O ≤ 0.20%; N ≤ 0.05%; H ≤ 0.015% (150ppm)

 

4. Practical Key Points

• Sampling should avoid the surface contaminated layer, and turn off the oxide scale
• Medical/aviation grade materials must be ultrasonically cleaned to prevent iron contamination
• At least one set of parallel samples shall be taken for each heat lot number, and re-inspection is required if the data deviation exceeds the tolerance

 

 

1. Routine Items

• Tensile test: Tensile strength, yield strength, percentage elongation after fracture, reduction of area.
• Hardness: Vickers HV, Brinell HB, Rockwell HRC, HV10 is commonly used
• Impact toughness: Charpy V-notch, low/room temperature impact
• Bending/shear test: Verify plasticity and formability

 

2. Advanced Items

• Fatigue performance: High-cycle fatigue, low-cycle fatigue, evaluate service life
• Fracture toughness KIC: Crack resistance
• High-temperature creep and rupture: Essential for aero-engines and hot-end components

 

3. Practical Key Points

• Sampling direction: Longitudinal/transverse/radial in accordance with standards
• Avoid tool marks, overheating and deformation during sample processing
• Calibrate the equipment before testing, and keep the ambient temperature stable at 23±5℃

 

 

1. Testing Content

• Grain size, α/β phase ratio and morphology
• Judgment of Widmanstätten structure, basket-weave structure and bimodal structure
• Inclusions, segregation, overheated structure, α embrittlement layer

 

2. Standard Process

• Sampling → Mounting → Coarse grinding → Fine grinding → Mechanical polishing
• Corrosion: Kroll's reagent (2%HF + 6%HNO₃ + 92%H₂O)
• Observation with metallographic microscope/SEM, photographing and grading

 

3. Judgment Key Points

• Grain size ≥ Grade 5 is qualified
• No continuous α grain boundaries, no abnormal segregation, no microcracks

 

 

1. Common Methods

• Ultrasonic Testing: The first choice for internal defects, such as blowholes, inclusions, cracks, with a sensitivity of Φ0.4–0.8mm flat-bottom hole
• Penetrant Testing: Surface open cracks, folds
• Eddy Current Testing : Surface/near-surface defects of conductive materials
• Radiographic Testing/Industrial CT: 3D imaging of complex structures and micro-pores

 

2. Applicable Scenarios

• Bars/plates/forgings: UT as the main method
• Precision/irregular parts: PT + UT
• Aviation/medical parts: 100% full inspection

 

 

• Salt spray test: For marine and humid environments
• Electrochemical test: Polarization curve, impedance spectrum
• Acid-base immersion test: Applicability for chemical industry working conditions
• Medical titanium alloys: Cytotoxicity, hemolysis, sensitization

 

 

• Dimensional tolerance: Coordinate measuring machine, caliper, micrometer
• Surface roughness: Ra value, Ra ≤ 0.8μm is usually required for aviation/medical use
• Surface defects: Oxide scale, cracks, tool marks, bumps, contamination

 

 

• Incoming material verification: Heat lot number, specification, quality certificate
• Composition assay: Spectrometry and gaseous element detection
• Mechanical property test: Tensile and hardness
• Metallographic structure analysis: Grain size and phase composition
• Non-destructive testing: UT/PT according to grade
• Dimensional and surface inspection: Full item review
• Data summary → Issue test report → Qualified for warehousing / Unqualified for isolation

 

 

Hydrogen embrittlement: Excessive H → Strictly control the atmosphere of smelting/heat treatment, and ensure H ≤ 150ppm in detection

High oxygen and nitrogen content: Increased strength and decreased plasticity → Protection with vacuum/inert atmosphere

Abnormal structure: Improper heat treatment → Optimize solution and aging process

Internal defects: Inclusions/porosity → Optimize forging/casting process

 

 

 

Testing and assay of titanium alloys is a full-process quality assurance from raw materials to finished products. Enterprises should establish a standardized testing system, and select CMA/CNAS certified third-party institutions for review of key components as a priority to achieve controllable quality and traceable liability.

 

Ruihang Group provide high-quality titanium and non-ferrous metal products with strict quality contol. Welcome to further cooperation,feel free to contact us by email:Sam.Rui@bjrh-titanium.com