Titanium copper composite bar

1. Purpose

This document specifies the ultrasonic testing method used to evaluate the bonding quality of titanium–copper clad bars.

The inspection is performed to verify the integrity of the cladding interface and to detect any unbonded areas between the titanium cladding and copper core.

2. Testing Equipment

2.1 Ultrasonic Flaw Detector

An A-scan pulse-echo ultrasonic flaw detector shall be used for the inspection.

The performance of the ultrasonic flaw detector shall comply with JB/T 10061 or an equivalent applicable standard.

2.2 Ultrasonic Probe

A straight-beam ultrasonic probe shall be used with the following specifications:

Parameter	Requirement
Probe Type	Straight-beam
Frequency	2.5–5 MHz
Crystal Diameter	10–20 mm

The final probe selection shall be suitable for the dimensions and acoustic characteristics of the titanium–copper clad bar.

2.3 Couplant

A suitable ultrasonic couplant shall be used to ensure effective transmission of ultrasonic energy between the probe and the inspection surface.

Acceptable coupling media include:

Clean water

Industrial inspection oil

2.4 Reference Test Bar

A reference test bar shall be used for sensitivity calibration.

The reference bar shall have:

The same material combination as the inspected clad bar

The same or equivalent dimensions

Similar acoustic characteristics

A fully bonded titanium–copper composite interface

3. Inspection Procedure

3.1 Inspection Method

The multiple back-wall echo reflection method shall be used to evaluate the bonding condition of the titanium–copper interface.

Inspection may be performed using either:

Contact ultrasonic testing

Immersion ultrasonic testing

The selected method shall provide adequate coverage and sensitivity for the entire inspection area.

3.2 Inspection Surface

For clad bars with rectangular, square, or drum-shaped cross-sections, ultrasonic inspection may be performed from any suitable axial surface to provide full coverage of the titanium–copper bonding interface.

The inspection arrangement shall ensure that the required interface area is effectively scanned.

3.3 Sensitivity Calibration

Before inspection, the ultrasonic testing system shall be calibrated using the reference test bar.

The instrument sensitivity shall be adjusted so that the fifth back-wall echo from the reference test bar reaches approximately 50% of the full screen height on the A-scan display.

This calibrated sensitivity shall be maintained as the inspection reference level during testing.

Recalibration shall be performed when required by the inspection procedure or whenever testing conditions change significantly.

3.4 Scanning Speed

The probe scanning speed shall not exceed:

150 mm/s

The scanning speed shall be sufficiently controlled to ensure reliable detection and evaluation of potential unbonded areas.

4. Evaluation Criteria

4.1 Identification of Bonded Areas

An area shall be considered bonded when the back-wall echo is clearly detected and no significant interface echo is observed at the calibrated inspection sensitivity.

4.2 Identification of Unbonded Areas

An area shall be classified as an unbonded area when:

The back-wall echo decreases significantly or disappears; and

A distinct interface echo is detected at the titanium–copper interface.

The indication shall be evaluated at the specified inspection sensitivity.

4.3 Determination of Unbonded Area Boundaries

During axial scanning, the boundary of an unbonded area shall be determined at the position where the interface indication disappears at the center of the ultrasonic probe.

The length of each unbonded area shall be measured along the axial direction.

5. Acceptance Criteria

The titanium–copper clad bar shall be considered acceptable when all detected unbonded areas comply with the requirements specified in Table 1.

Table 1 – Cladding Bonding Quality Acceptance Criteria

Inspection Area	Acceptance Requirement
Within 100 mm from each end	Maximum single unbonded axial length: <10 mm; cumulative unbonded length on one inspection plane: <20 mm
Other areas	Maximum single unbonded axial length: <50 mm; cumulative unbonded length per meter on one inspection plane: <100 mm

The above limits shall be evaluated on each applicable inspection plane.

6. Remarks

Surface roughness, surface condition, or minor geometric variations of the inspection surface shall not be interpreted as cladding defects unless they produce ultrasonic indications meeting the specified evaluation criteria.

Fluctuations in the back-wall echo caused by the internal structure or geometry of the copper core shall be considered during evaluation and shall not, by themselves, be classified as evidence of an unbonded area.

When an ultrasonic indication is detected, the affected area shall be rescanned to confirm the indication and determine its boundaries.

The ultrasonic testing results shall be recorded and retained as part of the quality inspection documentation.

Unless otherwise agreed with the customer, the acceptance criteria in this procedure shall apply to the titanium–copper clad bars covered by the relevant purchase order or technical specification.

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