Strength of Formed and Cut Threads of AA2017 and AA1050 Aluminum Alloys at Different States

The contribution of the states of the aluminum alloys on the formed and cut internal thread has been studied. An assembly consists of steel screw and aluminum tapped hole was chosen. The AA2017 and AA1050 in T3 and H14 states, respectively, as well as annealing states were considered for the tapped hole. Annealing treatment was performed on AA2017 to remove age-hardening and on both materials to remove work-hardening generated before or after the tapping process. Tensile and hardness tests were carried-out to evaluate the mechanical properties of the studied materials at different states. Pull-out test was used to create an actual loading in internal thread. The load-screw displacement relationship was recorded during pull-out test to reveal the intrinsic response of the thread and investigate the effects of tapping process at different materials states. The obtained results showed that the AA2017 has relatively a brittle shearing after reaching the ultimate strength whereas the AA1050 is characterized by a progressive shearing. The results also displayed that the material state has considerable effects on the shear strength of internal thread. The work-hardening generated by form tapping allowed to the improvement of shear strength of the formed thread. However, an imperfect cross-section of the formed thread profile seems to work against improvement by work-hardening.