To obtain reliable resistance spot welds that guarantees their satisfactory mechanical performance and improved crashworthiness in the vehicle autobody, it is vital to study the causes, conditions, ...and welding parameters resulting in the formation of defects and discontinuities in the welds. This work studies the weld discontinuities and defects that are likely to occur in resistance spot welding of 1-GPa transformation-induced plasticity steel. The causes of the formation of weld discontinuities and defects are discussed here. It is found that the rich chemistry and complex thermomechanical processing and thus special thermophysical properties of the alloy have significant impacts on the susceptibility of the welds to defects. The amount of heat input induced by the welding process also plays an important role on the defect formation. From the ductility ratio results, it can be said that there are critical heat input and critical nugget size for occurrence of the weld discontinuities and defects. The susceptibility of the resistance spot welds of the experimental alloy to early expulsion, liquation cracking, surface breaking cracks and their consequences on weld quality and performance are discussed here.
Friction stir welding (FSW) and friction stir processing (FSP) are two of the most widely used solid-state welding techniques for magnesium (Mg) and magnesium alloys. Mg-based alloys are widely used ...in the railway, aerospace, nuclear, and marine industries, among others. Their primary advantage is their high strength-to-weight ratio and usefulness as a structural material. Due to their properties, it is difficult to weld using traditional gas- or electric-based processes; however, FSW and FSP work very well for Mg and its alloys. Recently, extensive studies have been carried out on FSW and FSP of Mg-based alloys. This paper reviews the context of future areas and existing constraints for FSW/FSP. In addition, in this review article, in connection with the FSW and FSP of Mg alloys, research advancement; the influencing parameters and their influence on weld characteristics; applications; and evolution related to the microstructure, substructure, texture and phase formations as well as mechanical properties were considered. The mechanisms underlying the joining and grain refinement during FSW/FSP of Mg alloys-based alloys are discussed. Moreover, this review paper can provide valuable and vital information regarding the FSW and FSP of these alloys for different sectors of relevant industries.
•Mechanical, tribological, corrosion behavior, biocompatibility and antibacterial activity of Mg additively manufacturing are presented.•Different AM processes and post-processes treatments for Mg ...alloy are reviewed and summarized.•Benefits and restrictions of the Mg additively manufacturing are introduced.•The latest development of Mg additively manufacturing for industrial applications is presented.•Toughening mechanism and antibacterial mechanism Mg additively manufacturing is introduced.
Magnesium (Mg)-based materials are a new generation of alloys with the exclusive ability to be biodegradable within the human/animal body. In addition to biodegradability, their inherent biocompatibility and similar-to-bone density make Mg-based alloys good candidates for fabricating surgical bioimplants for use in orthopedic and traumatology treatments. To this end, nowadays additive manufacturing (AM) along with three-dimensional (3D) printing represents a promising manufacturing technique as it allows for the integration of bioimplant design and manufacturing processes specific to given applications. Meanwhile, this technique also faces many new challenges associated with the properties of Mg-based alloys, including high chemical reactivity, potential for combustion, and low vaporization temperature. In this review article, various AM processes to fabricate biomedical implants from Mg-based alloys, along with their metallic microstructure, mechanical properties, biodegradability, biocompatibility, and antibacterial properties, as well as various post-AM treatments were critically reviewed. Also, the challenges and issues involved in AM processes from the perspectives of bioimplant design, properties, and applications were identified; the possibilities and potential scope of the Mg-based scaffolds/implants are discussed and highlighted.
Ferritic–martensitic dual-phase (DP) steels are prominent and advanced high-strength steels (AHSS) broadly employed in automotive industries. Hence, extensive study is conducted regarding the ...relationship between the microstructure and mechanical properties of DP steels due to the high importance of DP steels in these industries. In this respect, this paper was aimed at reviewing the microstructural characteristics and strengthening mechanisms of DP steels. This review article represents that the main microstructural characteristics of DP steels include the ferrite grain size (FGS), martensite volume fraction (MVF), and martensite morphology (MM), which play a key role in the strengthening mechanisms and mechanical properties. In other words, these can act as strengthening factors, which were separately considered in this paper. Thus, the properties of DP steels are intensely governed by focusing on these characteristics (i.e., FGS, MVF, and MM). This review article addressed the improvement techniques of strengthening mechanisms and the effects of hardening factors on mechanical properties. The relevant techniques were also made up of several processing routes, e.g., thermal cycling, cold rolling, hot rolling, etc., that could make a great strength–ductility balance. Lastly, this review paper could provide substantial assistance to researchers and automotive engineers for DP steel manufacturing with excellent properties. Hence, researchers and automotive engineers are also able to design automobiles using DP steels that possess the lowest fuel consumption and prevent accidents that result from premature mechanical failures.
A Sm
2
Co
17
permanent magnet was successfully transient liquid phase bonded using AWS BNi-2 interlayer at 1100 °C for 60 min. Microstructural evolutions and chemical composition changes after TLP ...bonding of the samples were analyzed using optical microscopy, scanning electron microscopy and energy-dispersive spectroscopy. The changes of magnetic properties of the base material due to the TLP process were evaluated using vibrating sample magnetometry. It was found that the bonded sample by 50-μm-thick interlayer foil majorly contained athermally solidified zone and brittle second phase, indicating that the bonding time is not sufficient for joining, while the bonded sample by 25-μm-thick foil was almost solidified isothermally. Also, the results showed that a considerable increase in coercivity, remanence and also maximum energy product was occurred after TLP bonding of Sm
2
Co
17
permanent magnet. This increase was mainly attributed to the strong magnetic exchange coupling between FeCo- and Fe-rich borides (as soft magnets) and Sm–Co matrix (as hard magnet).
Welding of AISI H13 tool steel which is mainly used in mold making is difficult due to the some alloying elements and it high hardenability. The effect filler metal composition on the microstructural ...changes, phase evolutions, and hardness during gas tungsten arc welding of AISI H13 hot work tool steel was investigated. Corrosion resistance of each weld was studied. For this purpose, four filler metals i.e. ER 312, ER NiCrMo-3, ER 80S, and 18Ni maraging steel were supplied. Potentiodynamic polarization test and electrochemical impedance spectroscopy (EIS) were used to study the corrosion behavior of weldments. It was found the ER 80S weld showed the highest hardness owing to fully martensitic microstructure. The hardness in ER 312 and ER NiCrMo3 weld metals was noticeably lower than that of the other weld metals in which the microstructures mainly consisted of austenite phase. The results showed that the corrosion rate of ER 312 weld metal was lower than that other weld metals which is due to the high chromium content in this weld metal. The corrosion rate of ER NiCrMo-3 was lower than that of 18Ni maraging weld. The obtained results from EIS tests confirm the findings of potentiodynamic polarization tests.
As known, mechanical properties of gas tungsten arc welded 7075 Al alloys are not desirable and some techniques should be utilized in order to refine the microstructure and hence to improve the ...mechanical properties of weld joints. In this research work, the microstructure of gas tungsten arc welded 7075 Al alloy was modified by friction stir processing. Evaluation of the tensile strength of the welded joints showed that the tensile strength of the welded joint (228 MPa) increases up to 320 MPa after friction stir processing. In addition, electron backscattered diffractometry (EBSD) was used in order to study the microstructure and grain boundary character evolutions during arc welding and friction stir processing. It was revealed that as-cast dendritic microstructure of gas tungsten arc welded joint completely disappears during friction stir processing and veryfine equiaxed grains are formedinwelded joints. Analysis of EBSD data showed that friction stir processing of gas tungsten arc welded joints leads to increase of specific boundaries from 0.7% up to 7.8%. In addition, fraction of high angle boundaries increases after friction stir processing whichisresulted from dynamic recrystallization occurring during friction stir processing.
S500MC steel is a grade of high-strength low-alloy steel (HSLA) which is widely used in the automotive industry and for agricultural machinery and equipment. Considering properties of this alloy, ...selection of the welding process and parameters becomes essential to ensure that HSLA assemblies meet specific service requirements. In this work, mechanical and metallurgical properties of S500MC steel produced by autogenous laser beam welding (LBW) and automatic gas tungsten arc welding (GTAW) were compared. Tensile testing, metallography, hardness testing, and fractographic analysis were performed on the welded specimens, revealing that the heat input by these welding processes caused significant microstructural changes within the joints. In LBW samples, the heat input about 10 times lower than that in GTAW produced a finer microstructure, narrower fusion zone width, and smaller heat-affected zone. All fractures of the GTAW specimens occurred in the base metal, while all fractures of the LBW specimens occurred in the weld zone, both regardless of the heat input. GTAW joints exhibited higher mechanical properties (even higher than those obtained in the base metal) as compared to LBW joints.
Generally, the quality of a weld joint is directly influenced by the welding parameter settings. In order to obtain a weld metal with desired weld bead quality and profile, it is necessary to adjust ...suitable process parameters in welding instrument. In this work, numerical and graphical optimization techniques of the electron beam welding of ultra-thin FeCo-V magnetic foils were carried out using response surface methodology (RSM) based on central composite design. The procedure was established to improve the weld strength and increase the productivity by considering the welding parameters range of beam current (0.7–1.7 mA), beam voltage (40–50 kV), welding speed (150–500 mm/min), and focused position (−20 to 0 mm). Tensile test and microhardness measurements were employed in order to study the mechanical behaviors of the welds. Moreover, microstructural observation and phase analysis were carried out in order to elucidate the change mechanism of mechanical properties in the welded area. It was found that RSM can be considered as a powerful tool in experimental welding optimization, even when the experimenter has not a model for the process. Strong, efficient, and acceptable weld joints could be achieved using the optimum welding conditions.
SAF 2205 and IN X-750 were joined using the TLP method. The joining process was carried out at 1100 °C for different times using BNi-3 interlayer. Microstructural study and identification of the ...present phases in the bonding regions were performed using optical microscopy and scanning electron microscopy equipped with energy-dispersive X-ray spectroscopy and electron backscatter diffraction technique. Microhardness and shear strength tests were done to measure the mechanical properties. Different phases such as BN, Ni
3
B, Ni
2
B, CrB, Cr
2
B, and Ni
2
Si were formed in the bonding area. EBSD analysis results showed that the amount of the formed phases in the bonding area is a function of the bonding time. As the holding time increased, the amount of created phases in the bonding area increased from about 8 to 11 wt.%. The microhardness profile of the joining area also behaved differently as the bonding time changed. The maximum measured microhardness was about 850 HV which appeared in the athermally solidified zone of the bonded sample for 1 min. The maximum shear strength was observed in the bonded sample with complete isothermal solidification, approximately 72% of the shear strength of SAF 2205 and 85% of IN X-750.
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