Effect of Stress Ratio and Loading Mode on High Cycle Fatigue Properties of Extruded Magnesium Alloys

Abstract:

The aim of this study is to discuss an effect of stress ratio and loading mode on high cycle fatigue performances of extruded magnesium alloys. Axial loading fatigue tests under three conditions of stress ratio, R, of 0, -1 and-1.5, and also rotating bending fatigue tests have been performed in laboratory air at room temperature using hourglass shaped specimens of AZ31, AZ61, AZ80 and T5-treated AZ80 alloy. From the experimental results, some materials showed a specific stepwise S-N curve on which two knees appear. The shape of S-N diagram depended on a kind of tested materials, applied stress ratio and loading mode. It was suggested from the detail observation of fracture surface that fatigue crack initiation mechanism changed from a twin-induced failure mode at high stress amplitude level to a slip-induced one at low stress amplitude level. This transition was determined with the relation between the minimum stress during a fatigue cycle and the compressive yield stress at which deformation twin occurs.

• Periodical: Advanced Materials Research (Volumes 891-892)
• Pages: 557-562
• DOI: https://doi.org/10.4028/www.scientific.net/AMR.891-892.557
• Online since: March 2014
• Authors: Kazuaki Shiozawa*, Atsushi Ikeda, Tsuyoshi Fukumori
• Keywords: Crack Initiation, Fatigue, Loading Mode, Magnesium Alloy, Stress Ratio, Twin

References

[1] S. Kleiner and P.J. Uggowitzer, Mechanical anisotropy of extruded Mg-6%Al-1%Zn alloy, Materials Science and Engineering, A379 (2004) 258-263.

DOI: 10.1016/j.msea.2004.02.020

[2] J.P. Nobre, U. Noster, M. Kornmeier, A.M. Dias and B. Scholtes, Deformation asymmetry of AZ31 wrought magnesium alloy, Key Engineering Materials, 230-232 (2002) 267-270.

DOI: 10.4028/www.scientific.net/kem.230-232.267

[3] C.H. Cáceres, T. Sumitomo and M. Veidt, Pseudoelastic behaviour of cast magnesium AZ91 alloy under cyclic loading-unloading, Acta Materialia, 51 (2003) 6211-6218.

DOI: 10.1016/s1359-6454(03)00444-0

[4] H. Zenner, and F. Renner, Cyclic material behaviour of magnesium die castings and extrusions, International Journal of Fatigue, 24 (2002) 1255-1260.

DOI: 10.1016/s0142-1123(02)00042-7

[5] T.S. Srivatsan and L. Wei, The cyclic strain resistance, fatigue life and final fracture behavior of magnesium alloys, Engineering Fracture Mechanics, 56 (1997) 735-758.

DOI: 10.1016/s0013-7944(96)00127-0

[6] K. Shiozawa, M. Nagai, and T. Kaminashi, Low cycle fatigue behaviour of extruded magnesium alloys, 12th International Conference on Fracture, (2009, Ottawa) CD-ROM #01174.

[7] K. Shiozawa, M. Kashiwagi, T. Murai and T. Talahashi, Fatigue behaviour and fractography of extruded AZ80 magnesium alloys in very high cycle regime, Procedia Engineering, 2 (2010) 183-191.

DOI: 10.1016/j.proeng.2010.03.020