Assessment of tensile strength using small punch test for transversely isotropic aluminum 2024 alloy produced by equal channel angular pressing

The microstructures of metallic materials become extremely refined and their mechanical strengths exhibit considerable anisotropy when subjected to severe plastic deformation by equal channel angular pressing (ECAP). The small punch (SP) testing method was employed as a substitute for the standard tension test to assess the anisotropic tensile strength of materials produced by ECAP. SP testing is a viable alternative to standard tension tests because ECAP samples are usually limited to approximately 10 mm in length in the transverse direction perpendicular to the extrusion (longitudinal) direction of the ECAP process and the dimensions of the SP test specimen are 10 mm × 10 mm × 0.5 mm. The SP tests were performed using specimens of over-aged aluminum 2024 alloy subjected to three ECAP passes at 150 °C and extracted by wire cutting along the longitudinal and transverse axes. The failure surfaces of SP specimens after testing showed that failure was caused by shear deformation and that ECAP-processed materials displayed anisotropic strength. Based on these results, a method is proposed to assess tensile strength along both the transverse and the longitudinal axes of ECAP materials exhibiting anisotropic strength. The validity of the proposed method was verified through a comparison of its performance evaluating plastic flow strength with measurements obtained by tension tests along the longitudinal axis.