Study On Low Cycle Fatigue Behavior Of Al-Mg-Si-RE Alloy Processed By Equal Channel Angular Pressing

As one of the lightest engineering structural materials, aluminum alloys have beenwidely applied in industrial production. With the rapid development of aero andautomobile industries, the higher properties are required for aluminum alloys. Equalchannel angle pressing (ECAP) technology can substantially refine the grains by severepure shearing plastic deformation without changing the cross section of materials, hasreceived more and more attention and is an important processing technology for improvingthe mechanical properties of materials. Actually, many key components in practicalengineering application are often subjected to the alternating load, and thus the fatiguefailure has become an important factor which concerns the safety and economy for thosestructures used in various engineering fields. Therefore, the low-cycle fatigue behavior ofAl-8%Mg-0.6%Si-0.3%Sc alloy subjected to ECAP treatment with different passes androutes was investigated. And the morphologies of fatigue fracture surfaces were observedwith scanning electron microscope to clarify the fatigue fracture mechanism of ECAPedAl-8%Mg-0.6%Si-0.3%Sc alloy.The experimental results reveal that compared with the alloy ECAPed for one pass,two pass with route Bc and two pass with route C, the Al-8%Mg-0.6%Si-0.3%Sc alloyECAPed for two pass with route A has the finest grains. During fatigue deformation, theECAPed Al-8%Mg-0.6%Si-0.3%Sc alloy with different passes and routes（A、BC、C）exhibits the continuous cyclic strain hardening or initial cyclic strain hardening followedby cyclic stability. In general, the Al-8%Mg-0.6%Si-0.3%Sc alloy ECAPed for two passeswith route A shows the longer fatigue lives and higher cyclic deformation resistance atmost imposed total strain amplitudes. Moreover, the relation between elastic and plasticstrain amplitudes with reversal cycles to failure for the ECAPed Al-8%Mg-0.6%Si-0.3%Scalloy with different passes and routes exhibits a monotonic linear behavior, and can bedescribed by the Basquin and Coffin-Manson equations, respectively. In addition, underthe fatigue loading condition with total strain control mode, the fatigue cracks initiate transgranularly on the surface of fatigue specimens and propagate in a transgranular modefor the ECAPed Al-8%Mg-0.6%Si-0.3%Sc with different passes and routes.