Effects of Mn addition on the static and dynamic mechanical performance and fracture behavior of Al–8Si–xMn alloy sheets

This study thoroughly investigates the effect of Mn-containing dispersoids on the static and dynamic mechanical performance, as well as the fracture behavior of Al–8Si–(<0.01∼0.85) Mn alloy sheets, using OM, EBSD, LSCM, SEM/EDS, TEM, tensile tests, and fatigue tests. According to the data, as the Mn concentration increases, the number of Mn-containing dispersoids gradually increases, with their size remaining around 90 nm. Meanwhile, the recrystallization grain size growing from 16 to 29 μm, the texture type transitions from the Goss texture to the Cube texture, and finally, a strong {001} <140> special texture also appearing. The tensile strength of Al–8Si–xMn alloy sheets rises from 162 to 174 MPa, their yield strength rises from 68 to 78 MPa, and their elongation falls from 30 % to 27 %. A yield strength contribution model is established, and when the Mn concentration reaches 0.85 %, the Orowan strengthening contribution reaches its maximum, approximately 18 MPa. The tensile fracture mechanism of alloy sheets is known as ductile fracture. Additionally, the fatigue life of alloy sheets increases while the Mn concentration rises. The alloy sheet reaches its max fatigue life of 9.56 × 10 5 to 2.14 × 10 6 cycles, or around 2 to 4 times longer than the Mn-free alloy sheet, when the Mn concentration reaches 0.85 %. Fatigue crack always initiate at persistent slip bands. Based on the functional connection between fatigue life and Mn concentration, a fatigue life influencing factor I Mn is presented to quantitatively explain the impact of dispersoids amount on the alloy sheets' fatigue life and performance.