Increasing the Fatigue Life of VT1-0 Titanium under the Influence of a Constant Magnetic Field

Abstract

High-cycle fatigue tests of VT1-0 titanium samples were carried out under conditions of exposure to a constant magnetic field of various magnitudes and without it. It is shown that the use of a constant magnetic field with induction B = 0.3, 0.4, and 0.5 T leads to a multiple increase in the average number of cycles before the destruction of titanium samples VT1-0 by 64, 123, and 163%, respectively. Using scanning electron microscopy, it was found that the structure of a sample destroyed under fatigue testing conditions, regardless of the test mode, has three characteristic zones: a fatigue crack growth zone, an accelerated crack growth zone, and a fracture zone. It was found that the width of the fatigue crack growth zone depends on the magnetic field induction and reaches its maximum values (h = 264 μm) at B = 0.4 T, and during fatigue tests without a magnetic field, h = 182 μm. This indicates an increase in the critical crack length (the width of the fatigue crack growth zone) by a factor of 1.45. It is shown that the average distance between fatigue striations in titanium samples depends on the value of the magnetic induction of the magnetic field and decreases from 0.78 μm in the absence of a field to 0.49 μm at B = 0.5 T. The formation of a subgrain (fragmented) structure in the zone of fatigue crack growth in a titanium sample was established. The subgrain sizes correspond to the distance between the fatigue striations, which has a retarding effect on the movement of a microcrack. Taken together, the revealed facts indicate a higher resistance of the material to the propagation of a fatigue crack and an increase in its service life during fatigue tests in a magnetic field.