scholarly journals Crack-Free Welding of IN 738 by Linear Friction Welding

2011 ◽  
Vol 278 ◽  
pp. 446-453 ◽  
Author(s):  
Oyedele T. Ola ◽  
Olanrewaju A. Ojo ◽  
Priti Wanjara ◽  
Mahesh C. Chaturvedi
Keyword(s):  
Friction Welding ◽  
General Assumption ◽  
Fusion Welding ◽  
Second Phase ◽  
Linear Friction Welding ◽  
High Susceptibility ◽  
Linear Friction ◽  
Thermomechanical Simulation ◽  
Haz Cracking ◽  
Welding Processes

Inconel 738 (IN 738), like other precipitation-hardened nickel-base superalloys that contain a substantial amount of Al and Ti, is very difficult to weld due to its high susceptibility to heat-affected zone (HAZ) cracking during conventional fusion welding processes. The cause of this cracking, which is usually intergranular in nature, has been attributed to the liquation of various phases in the alloy, subsequent wetting of the grain boundaries by the liquid and decohesion across one of the solid-liquid interfaces due to on-cooling tensile stresses. In the present work, crack-free welding of the alloy was obtained by linear friction welding (LFW), notwithstanding the high susceptibility of the material to HAZ cracking. Gleeble thermomechanical simulation of the LFW process was carefully performed to study the microstructural response of IN 738 to the welding thermal cycle. Correlation between the simulated microstructure and that of the weldments was obtained, in that, a significant grain boundary liquation was observed in both the simulated specimens and actual weldments due to non-equilibrium reaction of second phase particles, including the strengthening gamma prime phase. These results show that in contrast to the general assumption of LFW being an exclusively solid-state joining process, intergranular liquation is possible during LFW. However, despite a significant occurrence of liquation in the alloy, no HAZ cracking was observed, which can be partly related to the nature of the imposed stress during LFW

Design of Numerical Simulations of Linear Friction Welding Processes: Issues and Difficulties

2015 ◽  
Vol 639 ◽  
pp. 451-458 ◽  
Author(s):  
Antonino Ducato ◽  
Davide Campanella ◽  
Gianluca Buffa ◽  
Livan Fratini
Keyword(s):  
Titanium Alloy ◽  
Phase Transformation ◽  
Friction Welding ◽  
Critical Analysis ◽  
Deformable Objects ◽  
Linear Friction Welding ◽  
Simulation Design ◽  
Advantages And Disadvantages ◽  
Linear Friction ◽  
Welding Processes

In this paper, a critical analysis of the technical difficulties and numerical issues in running simulations of linear friction welding processes is carried out. The focus of the paper is the comparison of different modeling strategies of a numerical analysis for the LFW process of Ti-6Al-4V titanium alloy, for which the thermal aspect strongly influences the mechanical behavior due to the phase transformation, taking place over a definite range of temperature. A 3D simulation campaign, conducted using the FEA code DEFORMTM, was considered in order to show advantages and disadvantages of each approach, including the most critic limitations and complexity in a correct simulation design using two deformable objects.

On the Solid Bonding Phenomena in Linear Friction Welding and Accumulative Roll Bonding Processes: Numerical Simulation Insights

2015 ◽  
Vol 639 ◽  
pp. 485-491 ◽  
Author(s):  
Davide Campanella ◽  
Gianluca Buffa ◽  
Livan Fratini ◽  
Marion Merklein
Keyword(s):  
Friction Welding ◽  
Accumulative Roll Bonding ◽  
Numerical Models ◽  
Material Behavior ◽  
Process Conditions ◽  
Main Process ◽  
Linear Friction Welding ◽  
Roll Bonding ◽  
Linear Friction ◽  
Welding Processes

Solid Bonding based welding processes allow to obtain defect free joints with low residual stress and low distortion. However, the engineering and optimization of solid bonding processes is difficult and requires a large number of time and cost consuming test trials. In this way, proper numerical models are essential tools permitting effective process design. The aim of this research was the comparison of the material process conditions during two different manufacturing processes taking advantage of the same metallurgical phenomenon, namely solid bonding. Linear Friction Welding, used to weld non-axisymmetric components and Accumulative Roll Bonding, used to increase the mechanical properties of sheet metals, were considered. Numerical models were set up, validated and used to design the process by studying the complex material behavior during the solid bonding of different aluminum alloys. An implicit approach was used for the Linear Friction Welding and Accumulative Roll Bonding processes, leading to the understanding of the main process variables influence on the field variables distribution and the occurrence of actual bonding.

scholarly journals Characterisation of Microstructure and Mechanical Properties of Linear Friction Welded α+β Titanium Alloy to Nitinol

2021 ◽  
Vol 11 (22) ◽  
pp. 10680
Author(s):  
Ateekh Ur Rehman ◽  
Nagumothu Kishore Babu ◽  
Mahesh Kumar Talari ◽  
Yusuf Usmani ◽  
Hisham Alkhalefah
Keyword(s):  
Friction Welding ◽  
Welding Process ◽  
Fusion Welding ◽  
Linear Friction Welding ◽  
Flow Strength ◽  
Turbofan Engine ◽  
Aircraft Fuel ◽  
Linear Friction ◽  
Dynamic Recrystallisation ◽  
Bypass Ratio

A variable area nozzle integrated into the design of a high-bypass-ratio turbofan engine effectively saves up to 10% in aircraft fuel consumption. Additionally, noise emissions can be lowered at airports during take-off and landing by having better control of the nozzle diameter. Shape memory capabilities of Nitinol alloys could be availed in the form of actuators in the construction of such a nozzle. However, these Nitinol actuators must be joined to Ti-6Al-4V, a prominent alloy making up most of the rest of the nozzle. Because of the huge differences in the physical and metallurgical properties of these alloys, fusion welding is not as effective as solid-state welding. In the current study, a linear friction welding process was adopted to join Ti-6Al-4V to Nitinol successfully. The effect of friction welding on the evolution of weld macro and microstructures; hardness and tensile properties were studied and discussed. The macrostructure of Ti-6Al-4V and Nitinol’s dissimilar joint revealed flash formation mainly on the Ti-6Al-4V side due to its reduced flow strength at high temperatures. Optical microstructures revealed fine grains in Ti-6Al-4V immediately adjacent to the interface due to dynamic recrystallisation and strain hardening effects. In contrast, Nitinol remained mostly unaffected. An intermetallic compound (Ti2Ni) was seen to have formed at the interface due to the extreme rubbing action, and these adversely influenced the tensile strength and elongation values of the joints.

scholarly journals Linear Friction Welding of an AZ91 Magnesium Alloy and the Effect of Ca Additions on the Weld Characteristics

Materials ◽  
2021 ◽  
Vol 14 (11) ◽  
pp. 3130
Author(s):  
Luis Angel Villegas-Armenta ◽  
Priti Wanjara ◽  
Javad Gholipour ◽  
Isao Nakatsugawa ◽  
Yasumasa Chino ◽  
...  
Keyword(s):  
Friction Welding ◽  
Weld Zone ◽  
Image Correlation ◽  
Second Phase ◽  
Linear Friction Welding ◽  
Az91 Magnesium Alloy ◽  
Strain Mapping ◽  
Fine Grain ◽  
Base Materials ◽  
Linear Friction

Solid-state welding offers distinct advantages for joining reactive materials, such as magnesium (Mg) and its alloys. This study investigates the effect of linear friction welding (LFW) on the microstructure and mechanical properties of cast AZ91 (Mg–9Al–1Zn) and AZ91–2Ca alloys, which (to the best knowledge of the authors) has not been reported in the literature. Using the same set of LFW process parameters, similar alloy joints—namely, AZ91/AZ91 and AZ91–2Ca/AZ91–2Ca—were manufactured and found to exhibit integral bonding at the interface without defects, such as porosity, inclusions, and/or cracking. Microstructural examination of the AZ91/AZ91 joint revealed dissolution of the Al-rich second phase in the weld zone, while the Mn containing phases remained and were refined. In the AZ91–2Ca/AZ91–2Ca joint, the weld zone retained Ca- and Mn-rich phases, which were also refined due to the LFW process. In both joint types, extensive recrystallization occurred during LFW, as evidenced by the refinement of the grains from ~1000 µm in the base materials to roughly 2–6 µm in the weld zone. These microstructural changes in the AZ91/AZ91 and AZ91–2Ca/AZ91–2Ca joints increased the hardness in the weld zone by 32%. The use of digital image correlation for strain mapping along the sample gage length during tensile testing revealed that the local strains were about 50% lower in the weld zone relative to the AZ91 and AZ91–2Ca base materials. This points to the higher strength of the weld zone in the AZ91/AZ91 and AZ91–2Ca/AZ91–2Ca joints due to the fine grain size, second phase refinement, and strong basal texture. Final fracture during tensile loading of both joints occurred in the base materials.

Effect of Process Parameters on Welding Variables during Linear Friction Welding of Ti-6Al-4V Alloy

2011 ◽  
Vol 314-316 ◽  
pp. 979-983
Author(s):  
Tie Jun Ma ◽  
Xi Chen ◽  
Wen Ya Li
Keyword(s):  
Titanium Alloy ◽  
Process Parameters ◽  
Friction Welding ◽  
Welding Process ◽  
Orthogonal Experimental Design ◽  
Linear Friction Welding ◽  
Influence Of Process Parameters ◽  
Linear Friction ◽  
Suitable Process ◽  
Axial Shortening

The orthogonal experimental design was conducted for linear friction welding of Ti-6Al-4V titanium alloy (TC4). The friction power and joint temperature were collected during the welding process. The influence of process parameters on the axial shortening was analyzed. The suitable process parameters were determined by investigating the joint appearance, the requirement of axial shortening and welding variables during welding. The results provide important reference for establishing process parameters of linear friction welding in practice.

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