Circumferential notch test based fracture toughness investigation of Al-Mg-Si Alloy composites reinforced with alumina and quarry dust

The influence of the notch diameter and the notch angle on the fracture toughness of aluminium alloy based composites (AMCs) determined using a notch tensile testing is investigated in this research. The study is motivated by the need to assure the validity and the reliability of the fracture toughness of AMCs determined by the testing method. The latter offers a more rapid assessment basis than the standard test approaches. Stir cast Al-Mg-Si alloy reinforced with 10 wt. % alumina and Al-Mg-Si alloy reinforced with 5 wt. % alumina (Al2O3) and 5 wt. % quarry dust (QD) are selected as AMCs for the study. Circumferentially notched specimens of a constant gauge length, but varied notch diameters and notch angles are prepared from the composites and utilized as variables in the study. The results obtained show that the plane strain condition is attained within the range of 1.25 ≤ ≤ 1.7, while the valid fracture toughness values referring to the ranges of 8.32 MPam1/2-12.67 MPam1/2 and 8.22 MPam1/2-11.08 MPam1/2 are obtained for 10 wt. % Al₂O₃ reinforced Al-Mg-Si alloy and 5 wt. % Al₂O₃ + 5 wt. % QD reinforced Al-Mg-Si alloy, respectively. It is also observed that the fracture toughness values decrease with an increase of the notch diameter, while no consistent relation can be established in respect to changes of the notch angle. The results are generally found to fall within the fracture toughness range reported in the literature for AMCs of a similar composition and a weight percentage evaluated using standard methods.