The intention of authoring this paper was giving the report of reviewing task of the previous researches done on the strengthening mechanisms and heat treatment of 7xxx aluminum alloys. The overall conclusion is that, the most powerful and so the most common strengthening mechanism in 7xxx alloys is the precipitation hardening (T6 heat treatment). On the other hand, stress corrosion is a problem in T6 treated 7xxx alloys, to address which, researchers have turned to special heat treatment called RRA (retrogression and re-aging) which picks the strength from T6, and stress corrosion resistance from T7x heat treatments.

Nowadays, researchers are very interested to investigate the dynamic behavior of the thin-walled structures during the machining process due to their broad application in aerospace, automotive industries and etc. One of the main problems in machining of thin-walled structures is unstable chatter vibrations, which causes the poor machined surface quality and decreases the system life span. In this regard, the main aim of this paper is to propose a practical method to solve the chatter instability problem during the milling process of thin-walled components. To this end, first the effects of geometrical parameters like workpiece height, thickness, and tool overhang, diameter and their ratios on the chatter stability are investigated. Then three dimensional stability lobe diagrams (SLDs) base on the mentioned parameters are presented for the first time. In which one can implement the mentioned diagrams to switch the unstable machining process to stable one by changing the value of the system parameters. Finally, the results obtained by the experimental test show that the presented three dimensional diagrams can be utilized to avoid chatter instability in the milling process.