Effect of Alternating Magnetic Field on the Fatigue Behaviour of EN8 Steel and 2014-T6 Aluminium Alloy

Abstract

The application of an alternating magnetic field (0.54 T) was observed to lead to an improvement in the fatigue endurance and an increase in Vickers microhardness and tensile strength of both EN8 steel and AA2014-T6 alloy. Fractography using scanning electron microscopy showed evidence of more ductile fracture features after treatment in contrast to untreated samples. The results of X-ray diffraction indicated formation of more compressive residual stresses following treatment; while examination by transmission electron microscopy showed evidence of fewer dislocations. In the case of the AA2014-T6 alloy; Guinier-Preston (GP) zones were also generated by the alternating magnetic field. However; the temperature increase during the treatment was too low to explain these observations. The results were attributed to the non-thermal effect of the alternating magnetic field treatment that led to depinning and movement of dislocations and secondary precipitation of copper.

Effect of Pulsed Magnetic Field on the Microstructure of QAl9-4 Aluminium Bronze and Its Mechanism

“…According to the above theory, it can be inferred that the dislocation in the aluminium bronze alloy becomes more easily depinned and moved under the influence of the original stress field, due to the change in the electronic energy state at the pinned place during the pulsed magnetic field treatment. On the one hand, the dislocation movement reduced the stress concentration caused by the dislocation pile-up, relaxed the original stress, and reduced the residual stress of the alloy, as verified by the significant reduction in residual stress in the magnetic field treatment of aluminium alloy [ 7 ], nickel–aluminium bronze [ 9 ], EN8 special steel [ 10 ], titanium alloy [ 26 ], and magnesium alloy [ 27 ]. On the other hand, the dislocation movement somewhat altered the grain boundary angle, resulting in an apparent reduction in LAGBs and the disappearance of twin boundaries, which lowered the system energy.…”

“…Compared with those that did not undergo magnetic field treatment, the microhardness of the NAB and aluminium alloy was increased by 6.2% and 4.5%, and the wear rate was reduced by 61% and 56%, respectively. Reference [ 10 ] reported that when cold-rolled EN8 steel and extruded AA2014-T6 aluminium alloy were also subjected to an alternating magnetic field with a magnetic induction intensity of 0.54 T, their respective fatigue lives were increased by 577% and 605%. Reference [ 11 ] investigated the effects of pulsed magnetic field treatment on a nickel-based alloy die and discovered that many fine γ′ phases precipitated in the γ matrix, the dislocation density increased, and the dislocation distribution became more uniform.…”

Effect of electropulsing on the fatigue resistance of aluminium alloy 2014-T6

“…It must be noted that the parameters of treatment (i.e., electric current/magnetic flux densities and pulse durations) used in this research were limited by the equipment that was utilised. However, the parameters utilised are not uncommon, and there are many other options available that generate higher magnetic field flux densities (i.e., higher than 0.12T) for much longer duration as used in a recent study [60]. Electropulsing is by its nature both a current inducing and a magnetic field inducing treatment for metals.…”

Influence of Constant Magnetic Field upon Fatigue Life of Commercially Pure Titanium

“…Extensive studies were also conducted concerning the influence of the magnetic fields upon the fatigue destruction of various metals and alloys [ 21 , 22 , 23 , 24 ].…”

“…The authors in [ 23 ] also observed an increase in the fatigue life of 35CrMo steel exposed to a magnetic field of 1.2–1.3 T of 10–15%. The authors of [ 24 ] associated the significant (more than three-fold) increase in the fatigue life of EN8 steel and AA2014-T6 alloy treated by a variable magnetic field of 0.54 T with the growth of residual compressive stresses in the near-surface layers of both metals as a result of the treatment. The problems of the influence of the external magnetic field on the fatigue properties of the materials being welded were studied in [ 25 , 26 , 27 , 28 ].…”