High-Strength Ultrafine-Grained Al-Mg-Si Alloys Exposed to Mechanical Alloying and Press-Forming: A Comparison with Cast Alloys.

A high-strength Al-Mg-Si alloy was prepared using mechanical alloying (MA) combined with press-forming (PF) technology, achieving a strength of up to 715 MPa and a hardness of 173 HB. The microstructures were comparatively analyzed with conventional cast Al-Mg-Si alloys using XRD, TKD, and TEM. The XRD results showed that the full width at half maximum (FWHM) of the alloy prepared by MA+PF was significantly broadened and accompanied by a shift in the diffraction peak. TKD revealed that the grain size of the MA+PF processed alloy was significantly reduced to approximately 260 nm, indicating substantial refinement compared to the cast alloy. Additionally, using TEM, it was found that the newly developed MA+PF alloy exhibited a distinct morphology of MgSi precipitation phases and a high density of stacking faults (SFs), characteristics that differed from those in the cast alloy. The significant enhancement in strength can be attributed to the synergistic strengthening effects of grain refinement, second-phase precipitation, and stacking fault strengthening, as synthesized and analyzed.