[2A4] Phased array ultrasonic testing of additively friction stir deposited AA2024 aluminium alloy samples
J Walker¹, B Mills¹, E Germano¹, Y Javadi¹, G Buffa², C MacLeod¹, A Gaghagan¹, G Pierce¹, C Mineo³ and S Tamimi¹
¹University of Strathclyde, UK
²University of Palermo, Italy
³Institute for High Performance Computing and Networking, Italy
This paper investigates additive friction stir deposition (AFSD) as an innovative solid-state metal additive manufacturing technique. AFSD’s unique attributes, such as reaching temperatures of approximately half of the material’s melting point, present a promising method for defect-free additive manufacturing. This process is essential in high-value applications involving intricate designs and costly materials. However, the complexities of manufacturing process parameters can potentially lead to the formation of various defects.
Defects in AFSD-manufactured samples, regardless of material, often occur as crack-shaped unbonded zones, especially in initial deposition layers due to low substrate temperatures. However, this improves in the upper layers where more heat is present, leading to better metallurgic bolding. Inadequate plastic deformation can also occur on the sides of the deposited wall, seen visually as flashes, due to the area not being located directly below the tool during processing. This contributes to incomplete metallurgic bonds. These unbonded areas look similar to cracks and can continue horizontally into the middle of the part, requiring trimming before post-treatment operations.
Therefore, detecting and optimising these parameters is crucial. To address this, we utilise phased array ultrasonic testing (PAUT) to analyse aluminium samples manufactured using AFSD. The samples used are three distinct AA2024 aluminium alloy walls, each 25 mm in diameter and 3 mm in thickness, manufactured under varying process conditions: tool rotation speeds of 800 r/min, 1100 r/min and 1400 r/min while maintaining consistent tool feed speed (360 mm/min) and tool force (8 kN).
After manufacturing, the samples were machined and side-drilled holes were introduced to calibrate the PAUT system. This set-up featured a 2.25 MHz, 20-element array (Sonatest Ltd, Milton Keynes, UK) with a pitch of 1.2 mm and an elevation of 12 mm. A Peak NDT LTPA phased array controller was also utilised, with 32:64 channel inputs and high dynamic range functionality (Peak NDT, Derby, UK).
The PAUT assessments were carried out successfully and were able to detect and accurately size all the artificially induced defects. Notably, an unidentified defect was detected in one of the samples, showing a clear warning against the utilisation of specific process parameters.
In summary, this study reveals the critical role of thorough defect detection in optimising the process of AFSD for improved additive manufacturing production.
Defects in AFSD-manufactured samples, regardless of material, often occur as crack-shaped unbonded zones, especially in initial deposition layers due to low substrate temperatures. However, this improves in the upper layers where more heat is present, leading to better metallurgic bolding. Inadequate plastic deformation can also occur on the sides of the deposited wall, seen visually as flashes, due to the area not being located directly below the tool during processing. This contributes to incomplete metallurgic bonds. These unbonded areas look similar to cracks and can continue horizontally into the middle of the part, requiring trimming before post-treatment operations.
Therefore, detecting and optimising these parameters is crucial. To address this, we utilise phased array ultrasonic testing (PAUT) to analyse aluminium samples manufactured using AFSD. The samples used are three distinct AA2024 aluminium alloy walls, each 25 mm in diameter and 3 mm in thickness, manufactured under varying process conditions: tool rotation speeds of 800 r/min, 1100 r/min and 1400 r/min while maintaining consistent tool feed speed (360 mm/min) and tool force (8 kN).
After manufacturing, the samples were machined and side-drilled holes were introduced to calibrate the PAUT system. This set-up featured a 2.25 MHz, 20-element array (Sonatest Ltd, Milton Keynes, UK) with a pitch of 1.2 mm and an elevation of 12 mm. A Peak NDT LTPA phased array controller was also utilised, with 32:64 channel inputs and high dynamic range functionality (Peak NDT, Derby, UK).
The PAUT assessments were carried out successfully and were able to detect and accurately size all the artificially induced defects. Notably, an unidentified defect was detected in one of the samples, showing a clear warning against the utilisation of specific process parameters.
In summary, this study reveals the critical role of thorough defect detection in optimising the process of AFSD for improved additive manufacturing production.
