Effect of forging on the low cycle fatigue behavior of cast AZ31B alloy

Abstract

The effect of forging on the low cycle fatigue (LCF) behavior of cast AZ31B was investigated.The forging process was conducted at a temperature of 450°C and speed of 390mm/min. Fully reversed (R ε =-1) strain controlled cyclic tests were performed on as-cast and forged materials under total strain amplitudes of 0.1%-1.2%. Forging eliminated the dendritic morphology and reduced β-phase intermetallics observed in the cast alloy. Additionally sharp basal texture and bimodal grain structure were developed. Generally, the forged material was found to exhibit longer fatigue life, especially at lower strain amplitudes. This was attributed to the grain refinement and the developed basal texture that changed the alloy's deformation behavior. Also, the forged material achieved significantly higher stresses at the same total strain amplitudes compared to cast AZ31B, and substantial cyclic hardening occurred during cyclic loading. At the same time, considerable tension-compression asymmetry was observed in the forged AZ31B during LCF testing. The Smith-Watson-Topper model and Jahed-Varvani energy model were employed and both models were found to accurately predict the experimentally obtained fatigue life of both alloy conditions. The Jahed-Varvani model accurately predicted fatigue life within a factor of 1.5 especially for the asymmetric behavior of forged AZ31B.

Mg-Alloys for Forging Applications—A Review

“…The tension and compression behavior as well as fatigue properties of forged AZ31 were investigated by Toscano et al [65,66]. As-cast stock material was homogenized at 450 • C for 3 h and formed directly afterwards.…”

Fatigue life improvement of cast ZK60 Mg alloy through low temperature closed-die forging for automotive applications

“…These residual twins can affect the fatigue response of the alloy in two ways. First, the interactions between the twin-twin bands and also twin-dislocations can lead to the crack initiation causing premature failure [14] [28]. Alternatively, some studies have suggested that the extension twinning can elongate the fatigue life in the light of crack growth retardation due to the roughness-induced crack closure [29].…”

Characterization of the corrosion performances of as‐cast Mg–Al and Mg–Zn magnesium alloys with microarc oxidation coatings

“…Recently, intensive research and development work has been conducted in both academic and industrial institutes to develop advanced materials processing and surface treatment technologies for replacing aluminum using Mg alloys in the design and manufacture of fatigue‐critical automotive components, such as the control arm . Three grades of Mg alloy (i.e., AZ31B, AZ80, and ZK60) were selected as the candidate materials for the development of cost‐effective forging processes for the fabrication of a lower control arm, due to their superior mechanical properties and excellent forgeability .…”

“…In the present work, the corrosion properties of as‐cast AZ31B, AZ80, and ZK60 alloys with and without MAO coatings have been investigated using advanced electrochemical and salt spray testing methods. The cast Mg alloys were used as the starting materials for development of the lower control arm . On the basis of the results of the corrosion properties of cast alloys, the corrosion and corrosion fatigue performances of the forged Mg alloys with and without coatings will be investigated in the follow‐up experiments.…”