scholarly journals Effect of size of alpha phases on cyclic deformation and fatigue crack initiation during fatigue of an alpha-beta titanium alloy

2018 ◽  
Vol 165 ◽  
pp. 15006
Author(s):  
Qiaoyan Sun ◽  
Changsheng Tan ◽  
Lin Xiao ◽  
Jun Sun
Keyword(s):  
Fatigue Crack ◽  
High Cycle Fatigue ◽  
Low Cycle Fatigue ◽  
Lamellar Microstructure ◽  
Alpha Phase ◽  
Cycle Fatigue ◽  
Beta Titanium Alloy ◽  
Beta Titanium ◽  
Alpha Beta ◽  
Equiaxed Alpha

Alpha phase exhibits equiaxed or lamellar morphologies with size from submicron to microns in an alpha-beta titanium alloy. Cyclic deformation, slip characteristics and crack nucleation during fatigue in different microstructures of TC21 alloy (Ti-6Al-2Sn-2Zr-3Mo-1Cr-2Nb-0.1Si) were systematically investigated and analyzed. During low-cycle fatigue, equiaxed microstructure (EM) in TC21 alloy exhibits higher strength, ductility and longer low-cycle fatigue life than those of the lamellar microstructure (LM). There are more voids in the single lamellar alpha than the equiaxed alpha grains. As a result, voids more easily link up to form crack in the lamellar alpha phase than the equiaxed alpha phase. However, during high-cycle fatigue, the fine lamellar microstructure (FLM) shows higher fatigue limit than bimodal microstructure (BM). The localized plastic deformation can be induced during high-cycle fatigue. The slip bands or twins are observed in the equiaxed and lamellar alpha phases(>1micron), which tends to form strain concentration and initiate fatigue crack. The localized slip within nanoscale alpha plates is seldom observed and extrusion/intrusion dispersedly distributed on the sample surface in FLM. This indicates that FLM show super resistance to fatigue crack which bring about higher fatigue limit than BM.

High and Low Cycle Fatigue of Orthorhombic Ti-22Al-27Nb Alloy

2005 ◽  
Vol 475-479 ◽  
pp. 589-594
Author(s):  
Masuo Hagiwara ◽  
A. Araoka ◽  
Satoshi Emura
Keyword(s):  
High Cycle Fatigue ◽  
Low Cycle Fatigue ◽  
Lamellar Microstructure ◽  
Control Mode ◽  
Load Control ◽  
Cycle Fatigue ◽  
Lamellar Morphology ◽  
R Ratio ◽  
Fatigue Mechanism

The effect of the lamellar morphology on the high cycle fatigue (HCF) and low cycle fatigue (LCF) behavior of the Ti-22Al-27Nb alloy was investigated. The HCF tests were performed in air at an R ratio of 0.1 in the load-control mode, whereas the LCF tests were performed in vacuum at 923 K in the strain-controlled mode. The specimens with fine lamellar microstructure exhibited a better resistance to HCF than those with coarse lamellar microstructure. The microstructure-insensitive behavior was, however, observed in the LCF tests at 923 K. The fatigue mechanism was discussed based on the concurrent observation of the initiation facet and the underlying microstructure, and the TEM observations.

Connection among the Characteristics of the Low Cycle Fatigue, High Cycle Fatigue and Fatigue Crack Growth

2007 ◽  
Vol 345-346 ◽  
pp. 533-536
Author(s):  
Gyula Nagy ◽  
János Lukács
Keyword(s):  
Fatigue Crack ◽  
Fracture Surface ◽  
High Cycle Fatigue ◽  
Fracture Behaviour ◽  
Low Cycle Fatigue ◽  
Test Results ◽  
Cycle Fatigue ◽  
General Validity ◽  
Steel Grades ◽  
Fracture Types

The material quality, the deformation rate, the temperature and the stress state influence mechanical behaviour and properties of different materials. Due to this great variety of the influencing factors we do not have one model of general validity describing the behaviour of materials, but we have to use a great number of material constants in order to characterize the properties. The exponents of the Manson-Coffin, the Basquin and the Paris-Erdogan laws were applied for the verification of the connection among the fatigue fracture types. Own measured values and test results can be found in the literature were used for the illustration of the connections. “Fracture surface”-s were determined for characterizing of different steel grades and their welded joints. It can be concluded that “fracture surface”-s are suitable for the describing of the fracture behaviour and the conversion of different fracture parameters of steels.

Characterization of precipitates of Ti3Al in a titanium alloy

1996 ◽  
Vol 54 ◽  
pp. 1008-1009
Author(s):  
X.D. Zhang ◽  
J.M.K. Wiezorek ◽  
D.J. Evanst ◽  
H.L. Fraser
Keyword(s):  
Titanium Alloy ◽  
High Temperature ◽  
Aircraft Engine ◽  
Alpha Phase ◽  
Microstructural Stability ◽  
Beta Titanium Alloy ◽  
Two Phase ◽  
Beta Titanium ◽  
Alpha Beta

A two phase alpha-beta titanium alloy, Ti-6Al-2Mo-2Cr-2Sn-2Zr-0.2Si (Ti-6-22-22S), has recently been reconsidered as a high temperature material for aircraft engine applications. This alloy exhibits specific strength and fracture toughness superior to those of Ti-6A1-4V. However, similar to other alpha-beta titanium alloys, microstructural stability is one of the major concerns regarding industrial application of Ti-6-22-22S, since changes of the microstructure during long term high temperature exposure significantly affect the performance of components. Two types of precipitates have been observed in Ti-6-22-22S alloys, namely silicides and alpha 2-Ti3Al. The presence of intermetallic precipitates, such as alpha 2-Ti3Al, in the parent alpha matrix has been reported to result in brittle behaviour of the alpha-beta alloys due to the formation of intense planar slip bands. The present paper presents results of the characterization of intermetallic alpha2-Ti3Al precipitates in the alpha phase by methods of scanning and transmission electron microscopy (SEM and TEM respectively).

Grain size and grain growth in an equiaxed alpha-beta titanium alloy

1973 ◽  
Vol 4 (11) ◽  
pp. 2519-2525 ◽  
Author(s):  
Ernest Levine ◽  
Ira Greenhut ◽  
Harold Margolin
Keyword(s):  
Grain Size ◽  
Titanium Alloy ◽  
Grain Growth ◽  
Beta Titanium Alloy ◽  
Beta Titanium ◽  
Alpha Beta ◽  
Equiaxed Alpha

scholarly journals Comparison of fatigue crack initiation behavior in different microstructures of TC21 titanium alloy

2018 ◽  
Vol 165 ◽  
pp. 04014
Author(s):  
Changsheng Tan ◽  
Qiaoyan Sun ◽  
Lin Xiao ◽  
Yongqing Zhao ◽  
Jun Sun
Keyword(s):  
Fatigue Crack ◽  
High Cycle Fatigue ◽  
Crack Nucleation ◽  
Fatigue Crack Initiation ◽  
Lamellar Microstructure ◽  
Cycle Fatigue ◽  
Electron Backscattered Diffraction ◽  
Slip Bands ◽  
Heterogeneous Deformation ◽  
Large Primary

Cyclic heterogeneous deformation, slip characteristics and crack nucleation with different microstructures, such as bimodal microstructure (BM) and fine lamellar microstructure (FLM) in TC21 alloy (Ti-6Al-2Sn-2Zr-3Mo-1Cr-2Nb-0.1Si), were systematically investigated and analyzed during high cycle fatigue at room temperature. The results demonstrated that the FLM microstructure possesses higher high-cycle fatigue strength than those of the BM one. For BM, the heterogeneous plastic deformation existed within the different large primary α phase, such as equiaxed primary α and primary α lath. The cracks at interfaces and slip bands easily coalesce with each other to form large cracks in BM. However, the α laths with similar morphology and size (nanosize) distributed uniformly in FLM and could relatively deform homogeneously in micro-region, which delayed the initiation of the fatigue crack. Based on the electron-backscattered diffraction (EBSD) analysis, it found that the strain was nonuniformly distributed in BM, however, it is relatively homogeneous in FLM. Moreover, lots of straight cracks are parallel and along single intrusions within the β grain which delays the coalescence of cracks.

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