Extrusion of Unhomogenized Castings of 7075 Aluminum via ShAPE
Tianhao Wang, Julián Escobar, Miao Song, Md. Reza‐E‐Rabby, Brandon Scott Taysom, Joshua Silverstein, Timothy Roosendaal, Darrell Herling, Scott Whalen
Abstract
Extrusion of unhomogenized castings of the 7075 aluminum (Al) alloy has been accomplished using shear assisted processing and extrusion (ShAPE). The simultaneous plastic deformation and heat generation during ShAPE rapidly fracture and dissolve interdendritic and intragranular secondary phases of Al-Zn-Mg-Cu, accomplishing homogenization in seconds rather than many hours in a furnace before extrusion. ShAPE thereby eliminates the energy-intensive and time-consuming homogenization step required to prepare as-cast microstructures for conventional extrusion. Concurrently, extensive grain refinement occurs due to gradient activation of dynamic recrystallization during ShAPE, which facilitates a threefold increase in extrusion speed compared to the conventional extrusion method. Evident enhancement of the mechanical properties of ShAPE + T6 samples is achieved, compared to the ASTM standard values for conventional extrusion products. The microstructural evolution pathway, involving the processes of grain refinement and secondary particle dissolution, is explained using scanning and transmission electron microscopy.