Investigation of the influence of cryogenic-temperature machining on ultrafine-grained chips and machined surface quality of solution-treated aluminum 7075 alloys Untersuchung des Einflusses der Tieftemperaturbearbeitung auf ultrafeinkörnige Späne und die Qualität der bearbeiteten Oberfläche von lösungsgeglühten Aluminium-Legierungen (7075)

Abstract

In this study, cryogenic-temperature formal machining technique was used to process solution-treated aluminum 7075 alloys, the mechanical properties, morphology, and microstructure of machined surface and produced chips are investigated. Results show machining temperature has a huge influence on chip and machined surface morphology, cryogenic-temperature machining chips and machined surfaces possess better surface integrity, chips are continuous and smoother, and machined surfaces are flatter. In contrast, room-temperature formal machining chips exhibit serrated cracks on their free surface and the machined surface produces more serious scaly spines phenomenon. Both cryogenic-temperature and room-temperature samples experience severe deformation, cryogenic-temperature machining alumium 7075 alloys max microhardness has enhanced from 98 HV 0.1 to 174 HV 0.1, and cryogenic-temperature samples’ microhardness is higher than corresponding room-temperature samples’ microhardness among all machining parameters. Cryogenic-temperature can effectively suppress dynamic recovery thus chips could store more dislocations and then possess smaller ultrafine-grained structures, accounting for higher microhardness. Besides cryogenic-temperature inhibits precipitation of solute cluster and second phase particles and plays a lubrication effect at tool-chip interface, thus cryogenic-temperature machining aluminum 7075 alloys could obtain superior machined surface quality/chip morphology to improve processability. (*: Equal contributi)