Low Cycle Fatigue Failure of AA7020 Aluminum Alloy at different heat treatments | ||
| Engineering and Technology Journal | ||
| Article 1, Volume 28, Issue 19, September 2010, Pages 982-998 PDF (567.08 K) | ||
| DOI: 10.30684/etj.28.19.19 | ||
| Abstract | ||
| The present work encompasses Low Cycle Fatigue (LCF) of the Al-alloy AA7020 with three conditions; annealing, natural aging and artificial aging. The LCF tests carried out using standard specimens cantilever beam types. Optical Light Microscope (OLM) and Scanning Electron Microscope (SEM) were employed to examine the fracture features .The results confirmed that AA7020- O sustained cyclic ha rdening, while 7020-T4 & 7020-T6 undergoing cyclic softening, therefore make the annealing conditions more resistance to LCF. The values of fa tigue str ength exponent (b) is varying from (-0.064) to (-0.14) and fatigue ductility exponent (c) from (-0.554) to (-0.60), whereas these values within the general limitation of the metals. The number of transition cycle (NT) for annealing condition is more comparing to the other conditions which emphasis that the annealing alloy will withstand more cycles before introducing the plastic zone. The information extracted from Engineering Stress-Strain curve; (σu/σy) as well as strain harden exponent (n) can be need to estimate the behavior of annealing and artificial alloy, while the natural aging alloy will need LCF testing to definite the conducting because of its "n" less than (1.2) and (σu/σy ) more than (1.4) .The SEM examination districted many point of cracks initiation for the three alloys at stresses more than Yield point. OLM investigation of the cross-section of fracture surface indicated the dominating of applied stress when it is more than Yield point of artificial aging alloy. Where the stress concentration is the most important role for annealing specimens because of companion of cycle strain hardening | ||
| Keywords | ||
| Low Cycle Fatigue; Strain; Li fe Of Aluminum Alloy at annealing; natural aging and ar tificial aging | ||
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