Dynamic strain aging in low cycle fatigue of duplex titanium alloys

The influence of strain rate on low-cycle fatigue (LCF) behavior of Fe-22Mn-0.6C twinning-induced plasticity (TWIP) steel is investigated by conducting LCF tests. The LCF tests are performed at a strain amplitude of 0-1.4% with strain rates of 8 Â 10 À4 s À1 , 2 Â 10 À3 s À1 , 8 Â 10 À3 s À1 , and 2 Â 10 À2 s À1 . The corresponding fatigue fracture morphologies and microstructure are also investigated. The results indicate that the TWIP steel shows initial cyclic hardening and cyclic saturation and then cyclic softening until final fracture at all strain rates. In addition, the fatigue life decreases with increasing strain rate due to enhanced dynamic strain aging (DSA). Moreover, the generation of persistent slip bands (PSBs) at high strain rates is also favorable for crack nucleation and fatigue crack growth, which is one of the primary reasons that lead to the premature failure of the fatigue specimens. At all given testing conditions, the fracture morphologies occur in a transgranular fracture mode.

show abstract

“…This would cause a greater dislocation density during cyclic deformation . Similar results was also observed in duplex titanium alloy …”

Section: Resultssupporting

confidence: 80%

“…Thus, the accumulated plastic damage in one cycle of high strain rate is higher than that of low strain rate at the same strain range. Furthermore, DSA is considered to promote non‐uniform deformation, which leads to local plastic deformation and rapid fatigue failure.…”

Section: Resultsmentioning

confidence: 99%

Effects of Strain Rate on Low‐Cycle Fatigue Behaviors of Fe–22Mn–0.6C TWIP Steel

Shen

Liu

et al. 2019

Adv Eng Mater

View full text Add to dashboard Cite

show abstract

“…The magnitude of serration amplitude was found to be higher at lower strain amplitude (0.4%) and decrease with increasing strain amplitude. A similar serrated flow phenomenon present in the hysteresis loops was also reported during strain-controlled LCF of Al-Zn-Mg alloy in a natural aging condition [39] and in other materials, e.g., annealed Zircaloy-2 [46], forged alloy 617M in the solution annealed condition [47], Inconel 718 superalloy [48], duplex Ti-6Al-4V and SP700 titanium alloys [49], and extruded AM50 magnesium alloy [50]. It should be noted that the serrated flow behavior is dependent on the strain rate and temperature [51][52][53].…”

Section: Tensile Propertiessupporting

confidence: 80%

Cyclic Deformation Behavior of A Heat-Treated Die-Cast Al-Mg-Si-Based Aluminum Alloy

Mohammed

Gupta

et al. 2020

Materials

View full text Add to dashboard Cite

The purpose of this investigation was to study the low-cycle fatigue (LCF) behavior of a newly developed high-pressure die-cast (HPDC) Al-5.5Mg-2.5Si-0.6Mn-0.2Fe (AlMgSiMnFe) alloy. The effect of heat-treatment in comparison with its as-cast counterpart was also identified. The layered (α-Al + Mg2Si) eutectic structure plus a small amount of Al8(Fe,Mn)2Si phase in the as-cast condition became an in-situ Mg2Si particulate-reinforced aluminum composite with spherical Mg2Si particles uniformly distributed in the α-Al matrix after heat treatment. Due to the spheroidization of intermetallic phases including both Mg2Si and Al8(Fe,Mn)2Si, the ductility and hardening capacity increased while the yield stress (YS) and ultimate tensile strength (UTS) decreased. Portevin–Le Chatelier effect (or serrated flow) was observed in both tensile stress–strain curves and initial hysteresis loops during cyclic deformation because of dynamic strain aging caused by strong dislocation–precipitate interactions. The alloy exhibited cyclic hardening in both as-cast and heat-treated conditions when the applied total strain amplitude was above 0.4%, below which cyclic stabilization was sustained. The heat-treated alloy displayed a larger plastic strain amplitude and a lower stress amplitude at a given total strain amplitude, demonstrating a superior fatigue resistance in the LCF regime. A simple equation based on the stress amplitude of the first and mid-life cycles ((Δσ/2)first, (Δσ/2)mid) was proposed to characterize the degree of cyclic hardening/softening (D): D=±(Δσ/2)mid − (Δσ/2)first(Δσ/2)first, where the positive sign “+” represents cyclic hardening and the negative sign “−“ reflects cyclic softening.

show abstract

“…3b. Similar symmetrical hysteresis loops were observed in titanium alloys and their joints at R ε = −1, 16,18,20 and the initial asymmetrical hysteresis loops at other strain ratios were also observed in titanium alloys at R ε = 0.1. 21 The stress amplitudes，plastic strain amplitudes and fatigue life of LFWed TC4 joint at different strain ratios are as plotted in Fig.…”

Section: Hardness and Fatigue Behavioursupporting

confidence: 78%

Microstructure and fatigue properties of linear friction welded TC4 titanium alloy joints

Wang

et al. 2017

Science and Technology of Welding and Joining

View full text Add to dashboard Cite

The welded joints are often subjected to cyclic stresses and high-strain-rate deformation resulting in worrisome fatigue failure. Therefore, it is necessary to evaluate the fatigue resistance and cyclic deformation characteristics of these weldments. Ti-6Al-4V-0.3Fe-0.1C-0.05N-0.015H-0.2O (TC4) titanium alloy joints were produced via linear friction welding and a sound joint was obtained. It was observed that fine subgrains formed in the weld zone where the hardness became higher. The strain ratio had a strong effect on the cyclic deformation characteristics of the joint, with hysteresis loops being different at different strain ratios. However, the difference of fatigue life of the joint was small with varying strain ratios. The stress amplitude of linear friction welded TC4 joint showed essentially cyclic softening until failure at all strain ratios. Fatigue cracks initiated from the near-surface of base metal and propagated by the formation of fatigue striations together with secondary cracks.

show abstract

Dynamic strain aging in low cycle fatigue of duplex titanium alloys

Cited by 21 publications

References 33 publications

Effects of Strain Rate on Low‐Cycle Fatigue Behaviors of Fe–22Mn–0.6C TWIP Steel

Effects of Strain Rate on Low‐Cycle Fatigue Behaviors of Fe–22Mn–0.6C TWIP Steel

Cyclic Deformation Behavior of A Heat-Treated Die-Cast Al-Mg-Si-Based Aluminum Alloy

Microstructure and fatigue properties of linear friction welded TC4 titanium alloy joints

Contact Info

Product

Resources

About