On the effect of the crystalline structure on fatigue: Comparison between body-centred metals (Ta, Nb, Mo and W) and face-centred and hexagonal metals

Abstract

The fatigue resistance for several body-centred pure metals (Nb, Ta, Mo and W) has been determined. The form of the fatigue curves are similar to those of iron and, as in this case, the fatigue limit is reached before 10⁷ cycles. It is also more generally confirmed that, when compared to some suitable static property, such as the ultimate tensile strength of the hardness, the fatigue of body-centred structures is much higher (FL/UTS 0·5-0·8) than that of face-centred or hexagonal structures such as nickel or cobalt (FL/UTS 0·3-0·4). The difference has to be related to the different behaviour of dislocations in the former structures because of the very high friction stress and easy cross slip characteristic of b.c.c. metals.