Friction, Wear and Surface Quality of 7055 Aluminum Alloy under Extreme Conditions

In this study, high speed cutting experiment of 7055 aluminum alloy treated by low temperature progressive aging was conducted under the extreme conditions at -60℃ and 300℃. Super depth of three-dimensional microscopic system was used to examine the tool worn surface morphology. The milling processing surface topography was explored by 3D probe-type Surface Plasmon Resonance Analyzer. The microstructures of 7055 aluminum before and after the cutting were comparatively investigated by using transmission electron microscopy. The results show that the main wear form of tool was abrasive wear with brittle tipping at -60℃. The main wear form of tool was oxidative wear and adhesive wear at 300℃. It is found that the high hardness and brittleness of 7055 aluminum alloy due to the cryogenic treatment at -60℃ led to the poor quality of processing surface. In contrast, the lower hardness and brittleness and higher toughness and ductility of material owing to the retrogression heat treatment at 300℃ were beneficial to the good quality of the processing surface.And the tool life was prolonged. By observing the TEM microstructure of the materials, it is shown that the discrete grain phases of 7055 aluminum alloy became tiny and fine after high speed cutting at -60℃. Most of the discrete phases of 7055 aluminum alloy disappeared after high speed cutting at 300℃. The microstructure retrogression phenomenon emerged.