This chapter analyzes the effects of Linear Friction Welding (LFW) on the impact behaviour of an aluminium matrix composite (AA2124-25%vol.SiCp) and an unreinforced Al alloy (AA2024). The aluminum based metal matrix composite (MMC) was obtained by powder metallurgy, forged and T4 heat-treated, while the Al alloy was supplied in the extruded and T4-heat treated condition. Optical Microscopy (OM) and Scanning Electron Microscopy (SEM) with Energy Dispersive Spectroscopy (EDS) were used to characterize the effects of the welding process on the microstructural characteristics of the LFW joints, which were obtained between similar (MMC-MMC, AA2024-AA2024) and dissimilar materials (MMC-AA2024). Instrumented impact tests were carried out on Charpy specimens, machined either from the base materials or from the LFW joints. The mechanisms of failure was investigated by SEM analyses of the fracture surfaces. The microstructure of the joints was found to be dependent on both the initial microstructure of the tested materials and the welding process. The LFW induced a reduction of the impact strength of the AA2024 alloy, while it had no relevant effects on the impact strength of the AA2124/25%SiCp composite. The impact energy of the dissimilar weld was comparable to that of the MMC joint, since fracture propagated mostly on the composite side. The fracture path was usually located along the thermomechanically affected zone in the similar joints.
Impact behaviour of similar and dissimilar linear friction welding joints between a 2024 Al alloy and a 2124-25%volSiCp composite.
GARAGNANI, Gian Luca;MERLIN, Mattia
2012
Abstract
This chapter analyzes the effects of Linear Friction Welding (LFW) on the impact behaviour of an aluminium matrix composite (AA2124-25%vol.SiCp) and an unreinforced Al alloy (AA2024). The aluminum based metal matrix composite (MMC) was obtained by powder metallurgy, forged and T4 heat-treated, while the Al alloy was supplied in the extruded and T4-heat treated condition. Optical Microscopy (OM) and Scanning Electron Microscopy (SEM) with Energy Dispersive Spectroscopy (EDS) were used to characterize the effects of the welding process on the microstructural characteristics of the LFW joints, which were obtained between similar (MMC-MMC, AA2024-AA2024) and dissimilar materials (MMC-AA2024). Instrumented impact tests were carried out on Charpy specimens, machined either from the base materials or from the LFW joints. The mechanisms of failure was investigated by SEM analyses of the fracture surfaces. The microstructure of the joints was found to be dependent on both the initial microstructure of the tested materials and the welding process. The LFW induced a reduction of the impact strength of the AA2024 alloy, while it had no relevant effects on the impact strength of the AA2124/25%SiCp composite. The impact energy of the dissimilar weld was comparable to that of the MMC joint, since fracture propagated mostly on the composite side. The fracture path was usually located along the thermomechanically affected zone in the similar joints.I documenti in SFERA sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
