Study Of Fatigue Behavior Of2A14Aluminum Alloy

The fatigue behavior of alloy2A14has been studied under the conditions ofcombining room temperature (RT) with air, RT with vacuum(10-3Pa) and vacuum(10-3Pa) with-190℃,respectively, by using fatigue machine, macro scope, scanningelectron microscope and transmission electron microscope.The results show that the fatigue life of alloy2A14decreases with increasing stressamplitude under the above conditions. With the same stress amplitudes, the fatigue lifeof alloy2A14at RT in vacuum is superior to that at RT in air and inferior to that at-190℃in vacuum. The low temperature plays a more important role than the vacuum on thefatigue performance of alloy2A14. The fatigue strength of alloy2A14, is130MPa～140MPa at RT in air, smaller than160MPa at RT in vacuum, and230MPa～250MPa at-190oC in vacuum, respectively.Under the condition of combining RT with air, the characteristics of the crackinitiation region on the fracture surface of alloy2A14are mainly radial steps and pores,while the crack propagation region is characterized by fatigue striations, whose spacingincrease with the stress amplitude increasing. Under the conditions of combining RTwith vacuum and vacuum with-190℃, slip traces are observed on the crack initiationregion, while slip traces, secondary cracks and pores distribute mainly on the crackpropagation region.Under above three conditions, the dislocation densities near to the fatigue fractureof alloy2A14increase with the increase of stress amplitudes. Low temperature haseffects on dislocation configuration and dislocation density. With the stress amplitudeof300MPa, the dislocation configuration appears as curled line and loop shapes at RTin vacuum, while it appears cellular substructures which have high density dislocationforming the wall and low density intracellular dislocation at-190℃in vacuum. Thedislocation configuration appears as curled line and loop shapes at RT in air and at RTin vacuum.