Effects of microstructural inhomogeneities and micro-defects on tensile and very high cycle fatigue behaviors of the friction stir welded ZK60 magnesium alloy joint

Yao, Chi; He, Chao; Yang, Kun; Zhang, Hong; Wang, Chong; Wang, Hongtao; Liu, Yongjie

doi:10.1016/j.ijfatigue.2019.01.016

Cited by 47 publications

(15 citation statements)

References 45 publications

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“…The stress intensity factors of FGA decrease with an increase in the fatigue cycles of the welded joint. However, it has been found in earlier studies [23,28,36] that the K FGA is a constant independent of the fatigue life which is related to the threshold value of the crack propagation. It can be found that the stress intensity factor corresponding to the pores originating from the crack origin of the welded joint decreases with an increase in the fatigue cycles.…”

Section: Discussionmentioning

confidence: 94%

“…FGA is the crack initiation zone, and the fatigue life of FGA is the crack initiation life [36]. In addition, it has been confirmed that the fatigue life of FGA accounts for the large part of the total fatigue life [22,23,36,37]. The fracture of the welded joint indicates that the crack originates from the welded pores.…”

Section: Discussionmentioning

confidence: 99%

“…The current state of the art of the EBW joints for metallic materials is the design life using the fatigue limit up to 10 7 cycles. However, it is now well understood that metallic materials experience fatigue fracture up to 10 10 cycles and assuming infinite fatigue life below fatigue limit is a conservative concept [22,23]. Hence, it is now extremely important to understand the fatigue behavior of EBW joints for design life up to 10 9 cycles.…”

Section: Introductionmentioning

confidence: 99%

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Influence of Welded Pores on Very Long-Life Fatigue Failure of the Electron Beam Welding Joint of TC17 Titanium Alloy

et al. 2019

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The electron beam welding process is widely used in the connection among titanium alloy material parts of aero-engines. Its mechanical properties need to meet the requirements of long life and high reliability. In this paper, the static strength and the fatigue failure behavior of the electron beam weldments of TC17 titanium alloy were investigated experimentally under low amplitude high frequency (20 kHz), and the mechanical response and failure mechanism under different external loading conditions were analyzed. In summary, the samples were found to have anisotropic microstructure. The tensile strength of the PWHT of TC17 EBW joint was ~4.5% lower than that of the base metal. Meanwhile, compared with the base metal, the fatigue strength was reduced by 45.5% at 109 cycles of fatigue life. The fracture analysis showed that the fatigue failure of the welded joint of TC17 alloy was caused by the welded pores and the fatigue cracks initiated from the welded pores. A fine granular area (FGA) was observed around the crack initiation region. The existence of pores caused the stress intensity factor of the fine granular area (KFGA) to be inversely proportional to the fatigue life. The KFGA calculation formula was modified and the fatigue crack propagation threshold of the welded joint of TC17 alloy was calculated (3.62 MPa·m1/2). Moreover, the influences of the effective size and the relative depth of the pores on the very long fatigue life of the electron beam welded joint of TC17 titanium alloy were discussed.

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Section: Discussionmentioning

confidence: 94%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Influence of Welded Pores on Very Long-Life Fatigue Failure of the Electron Beam Welding Joint of TC17 Titanium Alloy

et al. 2019

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“…This may be due to the low heat input generation; 70-80% of heat is generated through the interaction between the shoulder and workpiece during friction stir welding [33]. However, 2-20% of heat is generated from the plastic deformation and remaining heat from the interaction of the tool with the workpiece in weld [34]. The width of the weld zone increases at the shoulder interfacing surface area Fig.…”

Section: Weld Bead Surface and Macrostructurementioning

confidence: 99%

Effect of traverse speed on microstructure and mechanical properties of friction-stir-welded third-generation Al–Li alloy

Kumar

Acharya

Sethi

et al. 2020

J Braz. Soc. Mech. Sci. Eng.

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The aim of the study is to investigate the consequences of tool traverse speed on force and torque distribution of friction-stirwelded third-generation Al-Cu-Li alloy joints. The microstructure and corresponding mechanical properties of the joints are investigated on force and torque perspective. Thus, the contribution of the present work lies in establishing the relation between traverse speed and mechanical properties of the AA2050-T84 joint. Four welds have been considered at varying traverse speeds from 1 to 4 mm/s at constant tool rotational speed and tool tilt angle of 1400 rpm and 2°, respectively. A tool of H13 steel having a tapered screw-threaded pin profile was used. The investigation reveals that with the increase in traverse speed, longitudinal force (X-force), vertically downward force (Z-force) and spindle torque also increase. The grain size of the nugget zone reduces from 19.84 to 14.86 µm as traverse speed increases. It has been found that the mechanical strength of the joint increases as the traverse speed increases. The Vickers microhardness value increases from 115 HV 0.1 to 131 HV 0.1 in the nugget zone as traverse speed increases from 1 to 4 mm/s. The maximum tensile strength, % elongation and joint efficiency are 403.2 MPa, 7.2% and 75.5% for traverse speed of 4 mm/s. The tensile fracture samples are analyzed by scanning electron microscope and reveal ductile mode of fracture.

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“…However, the poor weldability of Mg alloys is performed due to their special pyroelectric and poor oxidation resistance [9,10]. In particular, conventional welding methods (such as, metal-arc inert gas, plasma arc and tungsten-arc inert gas) may lead to large residual stress, stress corrosion cracking sensitivity and evaporation loss [11]. Moreover, a brittle intermetallic phase (such as β-Mg 17 Al 12 ) is prone to being formed during the welding process, which leads to the decrease in the mechanical properties of friction stir-welded AZ31 magnesium alloys [12].…”

Section: Introductionmentioning

confidence: 99%

Refined Microstructure and Enhanced Hardness in Friction Stir-Welded AZ31 Magnesium Alloy Induced by Heat Pipe with Different Cooling Liquid

Zhang

Chen

et al. 2019

Metals

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The temperature field in welded plates has a significant influence on the microstructure and thereby their properties during friction stir welding (FSW). In this work, a self-designed heat pipe with different cooling liquid was applied in the FSW process for AZ31 magnesium alloy. The temperature fields, microstructures and properties of the welded joints were investigated. The peak temperatures and the durations of high temperature at both the advancing side and the retreating side decrease during the FSW process after applying the heat pipe and adding the ambient temperature water in the condensing tank. The top part of the weld nugget zone of the joint shows a significant decrease as well as its middle part due to the cooling effect of the heat pipe. The microstructure of the weld nugget zone is refined, associated with the increase in the hardness after applying the heat pipe. When the cooling liquid turns into ice water, grains in the weld nugget zone become significantly smaller and have a more homogeneous size. The mean value of hardness increases and the corresponding deviation is declined. Therefore, these results indicate that the application of the heat pipe and the employment of ice water as the cooling liquid can further refine the microstructure and enhance the strength of the material.

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Effects of microstructural inhomogeneities and micro-defects on tensile and very high cycle fatigue behaviors of the friction stir welded ZK60 magnesium alloy joint

Cited by 47 publications

References 45 publications

Influence of Welded Pores on Very Long-Life Fatigue Failure of the Electron Beam Welding Joint of TC17 Titanium Alloy

Influence of Welded Pores on Very Long-Life Fatigue Failure of the Electron Beam Welding Joint of TC17 Titanium Alloy

Effect of traverse speed on microstructure and mechanical properties of friction-stir-welded third-generation Al–Li alloy

Refined Microstructure and Enhanced Hardness in Friction Stir-Welded AZ31 Magnesium Alloy Induced by Heat Pipe with Different Cooling Liquid

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