Microstructural evolution and fatigue properties of severely deformed AA1050 aluminum alloy

- Effect of twist extrusion (TE) on the fatigue behavior of the AA1050 aluminum alloy.
- Samples of AA1050 are TE processed for 1, 2 and 4 passes.
- Tensile testing and rotational bending fatigue testing were performed.
- Fracture surface of the samples were analyzed.

In this article, the effect of twist extrusion (TE) on the fatigue behavior of the AA1050 aluminum alloy is investigated. For this purpose, samples of AA1050 are TE processed for 1, 2 and 4 passes. Tensile testing and rotational bending fatigue testing were performed on samples extracted from the surface of the TE specimens. As well, the correlation between microstructure, tensile properties and fatigue response are discussed. The un-deformed AA1050 sample showed a yield strength (YS) of 26.6 MPa and ultimate tensile strength (UTS) of 46.1 MPa and resisted the 38 MPa bending stress for 373,000 cycles. While the YS and UTS increased after TE, the fatigue life of TE processed specimens reduced compared with the un-deformed sample. Indeed, the fatigue life reduced to 335,168, 299,798 and 259,260 cycles after 1, 2 and 4 passes of TE, respectively. Reducing fatigue life was attributed to smaller strength ratio, i.e., UTS/YS, achieved after TE processing. Analyzing the fracture surface of the TE samples showed that the cracks were initiated from preferential locations and moved towards center leading to ultimate ductile fracture at the center. The area of ductile fracture was found to be reduced in TE processed specimens while the widths of striations were increased.