On the effect of β phase on the microstructure and mechanical properties of friction stir welded commercial brass alloys.
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ABSTRACT:
SUBMITTER: Heidarzadeh A
PROVIDER: S-EPMC4688973 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:This work was undertaken in an attempt to ascertain the generic characteristics of fatigue behavior of friction-stir welded aluminum alloys. To this end, different alloy grades belonging to both the heat-treatable and non-heat-treatable types in both the cast and wrought conditions were studied. The analysis was based on the premise that the fatigue endurance of sound welds (in which internal flaws and surface quality are not the major issues) is governed by residual stress and microstructure. Considering the relatively low magnitude of the residual stresses but drastic grain refinement attributable to friction-stir welding, the fatigue performance at relatively low cyclic stress was deduced to be dictated by the microstructural factor. Accordingly, the fatigue crack typically nucleated in relatively coarse-grained base material zone; thus, the fatigue strength of the welded joints was comparable to that of the parent metal. At relatively high fatigue stress, the summary (i.e., the cyclic-plus residual-) stress may exceed the material yield strength; thus, the fatigue cracking should result from the preceding macro-scale plastic deformation. Accordingly, the fatigue failure should occur in the softest microstructural region; thus; the fatigue strength of the welded joint may be inferior to that of the original material.
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Project description:The microstructure and texture of materials significantly influence the mechanical properties and fracture behavior; the effect of microstructure in different zones of friction stir-welded joints of 7A52 aluminum alloy on fracture behavior was investigated in this paper. The microstructural characteristics of sections of the welded joints were tested using the electron backscattered diffraction (EBSD) technique. The results indicate that the fracture is located at the advancing side of the thermomechanically affected zone (AS-TMAZ) and the stir zone (SZ) interface. The AS-TMAZ microstructure is vastly different from the microstructure and texture of other areas. The grain orientation is disordered, and the grain shape is seriously deformed under the action of stirring force. The grain size grows unevenly under the input of friction heat, resulting in a large amount of recrystallization, and there is a significant difference in the Taylor factor between adjacent grains and the AS-TMAZ-SZ interface. On the contrary, there are fine and uniform equiaxed grains in the nugget zone, the microstructure is uniform, and the Taylor factor is small at adjacent grains. Therefore, the uneven transition of microstructure and texture in the AS-TMAZ and the SZ provide conditions for crack initiation, which become the weak point of mechanical properties.
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Project description:According to the actual size parameters, the finite element model (FEM) of friction stir welding (FSW) was established, and the FEM was updated by experiments. The FSW of the 2A14-T6 high-strength aluminum alloy was simulated under a reasonable welding process parameter range, and the welding process parameters with good simulation effect were determined. The test was carried out under the same parameters, and the axial force of the FSW tool and temperature of the workpiece measuring point were collected. The comparison between the simulated data and the experimental data is reasonable, indicating the correctness of the FEM. The microstructure analysis of the welded joint shows that the grain size in the upper part of the weld nugget was smaller than that in the middle and lower parts, and there are obvious boundaries of grain size in each region of the joint. The hardness of the joint in the upper layer is higher than that in the middle and lower layers, and the minimum Vickers hardness value of the joint appears near the interface between the thermo-mechanically affected zone and the heat-affected zone on both sides of the weld. Tensile testing shows that the strength coefficient of the joint reaches 82.5% under this process parameter, and the sample breaks at the intersection of the material flow during stretching. After analyzing the final mechanical properties of the joint, we found that a degree of aerospace application can be achieved. Under this parameter, the welding test was carried out on the top cover of the rocket fuel tank. Firstly, melon valve welding, which is relatively difficult in welding conditions, was carried out, and a high-quality joint with good surface and no defects was obtained.
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Project description:Friction stir spot welding (FSSW) was established to compete reasonably with the reverting, bolting, adhesive bonding as well as resistance spot welding (RSW) which have been used in the past for lap joining in automobile, aerospace, marine, railways, defence and shipbuilding industries. The use of these ancient and conventional joining techniques had led to increasing material cost, installation labour, and additional weight in the aircraft, shipbuilding, and other areas of applications. All these are disadvantages that can be overcome using FSSW. This research work carried out friction stir spot welding on 5058-H116 aluminium alloy by employing rotational speed in the step of 300 rpm ranges from 600 rpm to 1200 rpm with a no travel speed. It was noted that the dwell times were in the step of 5 s varying from 5 s to 15 s while the tool plunge rate was maintained at 30 mm/min. In this dataset, a cylindrical tapered rotating H13 Hot-working steel tool was used with a probe length of 5 mm and probe diameter of 6 mm, it has a shoulder diameter of 18 mm. The tool penetration depth (plunge) was maintained at 0.2 mm and the tool tilt angle at 2°. Structural integrity was carried out using Rigaku ultima IV multifunctional X-ray diffractometer (XRD) with a scan voltage of 40 kV and scan current of 30 mA. This was used to determine crystallite sizes, peak intensity, d-spacing, full width at half maximum intensity (FWHM) of the diffraction peak. TH713 digital microhardness equipment with diamond indenter was used for microhardness data acquisition following ASTM E92-82 standard test. The average Vickers hardness data values at different zones of the spot-welds were captured and presented.
| S-EPMC8129645 | biostudies-literature
Project description:The present study was carried out to evaluate how the friction stir spot welding (FSSW) process parameters affect the temperature distribution in the welding region, the welding forces and the mechanical properties of the joints. The experimental study was performed by means of a CNC machine tool obtaining FSSW lap joints on AA7050 aluminum alloy plates. Three thermocouples were inserted into the samples to measure the temperatures at different distance from the joint axis during the whole FSSW process. Experiments was repeated varying the process parameters, namely rotational speed, axial feed rate and plunging depth. Axial welding forces were measured during the tests using a piezoelectric load cell, while the mechanical properties of the joints were evaluated by executing shear tests on the specimens. The correlation found between process parameters and joints properties, allowed to identify the best technological window. The data collected during the experiments were used to validate a simulation model of the FSSW process, too. The model was set up using a 2D approach for the simulation of a 3D problem, in order to guarantee a very simple and practical solution for achieving results in a very short time. A specific external routine for the calculation of the thermal energy due to friction acting between pin and sheet was developed. An index for the prediction of the joint mechanical properties using the FEM simulations was finally presented and validated.
| S-EPMC5512355 | biostudies-other
Project description:Additive manufacturing is a key component of the fourth industrial revolution (IR4.0) that has received increased attention over the last three decades. Metal additive manufacturing is broadly classified into two types: melting-based additive manufacturing and solid-state additive manufacturing. Friction stir additive manufacturing (FSAM) is a subset of solid-state additive manufacturing that produces big area multi-layered components through plate addition fashion using the friction stir welding (FSW) concept. Because of the solid-state process in nature, the part produced has equiaxed grain structure, which leads to better mechanical properties with less residual stresses and solidification defects when compared to existing melting-based additive manufacturing processes. The current review article intends to highlight the working principle and previous research conducted by various research groups using FSAM as an emerging material synthesizing technique. The summary of affecting process parameters and defects claimed for different research materials is discussed in detail based on open access experimental data. Mechanical properties such as microhardness and tensile strength, as well as microstructural properties such as grain refinement and morphology, are summarized in comparison to the base material. Furthermore, the viability and potential application of FSAM, as well as its current academic research status with technology readiness level and future recommendations are discussed meticulously.
| S-EPMC10095819 | biostudies-literature
Project description:Friction stir processing (FSP) manufacturing technology was used to fabricate medium Mn advanced high-strength steel in this study. The mechanical properties and microstructure of the steel fabricated using FSP were investigated. The steel obtained a total elongation of 35.1% and a tensile strength of 1034.6 MPa, which is about 59% higher than that of the steel without FSP. After FSP, a gradient structure occurs along the thickness direction. Specifically, across the thickness direction from the base material zone to the transition zone and finally to the stirring zone, both the grain size and austenite fraction decrease while the dislocation density increases, which results from the simultaneous effect of severe plastic deformation and recrystallization during FSP. Due to the gradient structure, an obvious difference in the strain across the thickness direction of the steel occurs during the deformation process, resulting in significant hetero-deformation-induced (HDI) strengthening. The deformation mechanism analysis reveals that HDI strengthening and dislocation strengthening are the main factors in the improvement in the strength-ductility balance. The obtained knowledge sheds light on the process of fabricating medium Mn steels with excellent properties using FSP manufacturing technology.
| S-EPMC11356244 | biostudies-literature
Project description:The data presented in this article are related to the research article entitled "Cyclic Shear behavior of conventional and harmonic structure-designed Ti-25Nb-25Zr β-titanium alloy: Back-stress hardening and twinning inhibition" (Dirras et al., 2017) [1]. The datasheet describes the methods used to fabricate two β-titanium alloys having conventional microstructure and so-called harmonic structure (HS) design via a powder metallurgy route, namely the spark plasma sintering (SPS) route. The data show the as-processed unconsolidated powder microstructures as well as the post-SPS ones. The data illustrate the mechanical response under cyclic shear loading of consolidated alloy specimens. The data show how electron back scattering diffraction(EBSD) method is used to clearly identify induced deformation features in the case of the conventional alloy.
| S-EPMC5832645 | biostudies-literature
Project description:K-TIG (Keyhole Tungsten Inert Gas) method is a new, emerging welding technology that offers a significant acceleration of the joining process, even for very thick plates. However, its potential for welding of certain materials is still unknown. Particularly challenging are duplex steels as this technology does not allow the use of a filler material, which is crucial for these steels and for weld joint microstructure adjustment. In order to demonstrate the suitability of this technology for single-pass welding of 1.4462 duplex steel detailed studies of the microstructure of the weld joints obtained for different linear energies were carried out and discussed with respect to their mechanical properties. According to the results obtained, the heat-affected zone (HAZ) shows a microstructure similar to the HAZ of duplex steel welded with the traditional TIG multi-pass methods. However, the weld, due to the lack of filler material, had a microstructure different to that typical for duplex steel welded joints and was also characterized by an increased content of ferrite. However, all joints, both in terms of microstructure and mechanical properties, met the requirements of the relevant standards. Moreover, the K-TIG process can be carried out in the linear energy range typical of duplex steel welding, although further optimization is needed.
| S-EPMC8708518 | biostudies-literature
Project description:BackgroundThe interaction between the material and the organism affects the survival rate of the orthopedic or dental implant in vivo. Friction stir processing (FSP) is considered a new solid-state processing technology for surface modification.PurposeThis study aims to strengthen the surface mechanical properties and promote the osteogenic capacity of the biomaterial by constructing a Ti-6Al-4V (TC4)/zinc (Zn) surface nanocomposites through FSP.MethodsFSP was used to modify the surface of TC4. The microstructures and mechanical properties were analyzed by scanning electron microscopy, transmission electron microscopy, nanoindentation and Vickers hardness. The biological properties of the modified surface were evaluated by the in vitro and in vivo study.ResultsThe results showed that nanocrystalline and numerous β regions, grain boundary α phase, coarser acicular α phase and finer acicular martensite α' appeared because of the severe plastic deformation caused by FSP, resulting in a decreased elastic modulus and an increased surface hardness. With the addition of Zn particles and the enhancement of hydrophilicity, the biocompatibility was greatly improved in terms of cell adhesion and proliferation. The in vitro osteogenic differentiation of rat bone marrow stromal cells and rapid in vivo osseointegration were enhanced on the novel TC4/Zn metal matrix nanocomposite surface.ConclusionThese findings suggest that this novel TC4/Zn surface nanocomposite achieved by FSP has significantly improved mechanical properties and biocompatibility, in addition to promoting osseointegration and thus has potential for dental and orthopedic applications.
| S-EPMC5880573 | biostudies-literature