Very High Cycle Fatigue Properties and Fracture Types of Ti-6Al-4V Alloy

Abstract

To investigate the fatigue characteristics and the frecture feature of Ti-6Al-4V in very high cycle region, uniaxial tension fatigue tests were carried out. The S-N diagram showed a complex folding shape, which corresponded to the locations of the fracture origins; i. e., surface-originating fractures in high stress level and interior-originating fractures in low stress level. In this study, observed also were interference type fractures in which the main crack was formed by the coalescence of a surface-originating crack and interior-originating cracks in low stress level.

Internal fatigue crack initiation in drawn Ti–6Al–4V wires

“…The markings on facets in this work are additional signs that there could indeed be a wear mechanism involved in internal crack initiation in Ti-6Al-4V. 36 The explanation of the presence of markings on facets in these experiments, and the absence of these markings in similar publications, 3,7,8,10,11,17,20 can be sought in the crystallographic texture of the alpha phase, which is different for the wire-drawn samples in this study compared to the forged rods used in other studies. It has been reported that facets are parallel to certain crystallographic planes, in most cases the basal plane 7,12,27,32,37,38 or the prismatic plane, 7,27 which means that the spatial angles of the facet planes are linked to the texture.…”

EBSD‐assisted fractography of sub‐surface fatigue crack initiation mechanism in the ultrasonic‐shot‐peened βeta‐type titanium alloy

“…It can be concluded that the sub‐surface crack initiation in the present case was not dominated by inclusions, but by some metallurgical factor in Ti alloy. In Ti‐6Al‐4V with α + β microstructure, Oguma et al had revealed that the sub‐surface crack initiation without inclusions occurred owing to the cleavage fracture of α‐phase in α + β microstructure, and Heinz and Eifler concluded that the sub‐surface crack initiated at the position with the lowest portion of β phase . The other examples of the sub‐surface crack initiation without inclusions in Ti‐6Al‐4V and Ti‐5Al‐5Mo‐5V‐3Cr‐1Zr were demonstrated by Liu et al and Huang et al, respectively.…”

Fatigue crack propagation properties of Ti–6Al–4V in vacuum environments

“…In previous studies, it is reported that the granular region is formed under the condition of vacuum or similar environments and repeated contacts of the fracture surfaces [6][7][8][9]. One of the differences between air and vacuum environments is the difference of gas adsorption.…”

“…vacuum-like environment. The properties of the sub-surface fracture have been investigated from the point of view of environment around the fatigue crack [6][7][8][9]. Fatigue tests until very high cycle regime were conducted, and observation of fracture surfaces revealed that a unique fine concave-convex agglutinate (hereinafter called Granular Region) formed on the fracture surface of sub-surface fractures, as shown in Fig.1 [4,5].…”