Gallium-assisted diffusion bonding of stainless steel to titanium; microstructural evolution and bond strength

Strong joints between stainless steel 304L and pure titanium (grade-2) were made using the novel method of “gallium-assisted diffusion bonding”. The microstructural evolution and interfacial reactions were investigated in detail. The possible mechanisms of phase changes at the joint interface when bonding with and without a nickel interlayer were identified. Layers of FeTi and (Fe,Cr)2Ti intermetallic compounds were found at the reaction zone in the case of direct bonding, whereas (Fe,Ni)Ti and Fe2Ti phases were identified in the reaction zone of the samples bonded using nickel interlayers. A layer of αFe was observed on the steel side of the reaction zone in both the cases, probably due to the enrichment of Cr at the interface. The diffusion of gallium led to formation of a layer of αTi, while the diffusion of Fe and Ni assisted in the formation of a duplex (α+β)Ti phase in the inter-diffusion zone. The joints fractured along the intermetallic layers at the interface, during tensile testing, with limited ductility. The maximum tensile strengths of the bonded samples were 280 and 313 MPa with and without nickel interlayer, respectively. The latter equals 92% of the tensile strength of the pure grade-2 titanium used in this work (i.e. 340 MPa)

The Influence of Friction Time on the Joint Interface and Mechanical Properties in Dissimilar Friction Welds

The welding of dissimilar materials is one of the challenging issues in thefabrication industry to obtain required quality welds using fusion weldingmethods. However, some processes recently improved interface bondingwith low joint strength. Unfortunately, the major intermetallic compoundscould not alleviate from the joint interface. Alternatively, solid-statewelding methods revealed fewer intermetallics at the joint interface fordissimilar material welds. Among them, friction welding was chosen to joinincompatible materials with the necessary properties successfully. Frictiontime is a critical parameter for obtaining strong welds through frictionwelding, apart from friction pressure, forging pressure, forging time, androtational speed. Variability of friction time can change the strength offriction by changing mechanical properties such as tensile strength. Thischange of tensile strength is typically influenced by the intermixing region,dependent on friction time. In this experiment, carbon steel and stainlesssteel have been friction welded to test the impact of friction time on thejoint interface where the substrate’s faying surface meets. This interfaceconsists of the intermixing region of the two materials on which the frictionwelding is performed. The results showed an interesting variation in tensilestrength, with varying friction time. The width of the intermixing zoneincreased gradually with friction time until and decreased with the furtherincreasing. The strength of the welds obtained was the highest of 730 MPaat a friction time of 4 s and fell as friction time’s increased value after 4 s

Advancements and Challenges in Additively Manufactured Functionally Graded Materials: A Comprehensive Review

This paper thoroughly examines the advancements and challenges in the field of additively manufactured Functionally Graded Materials (FGMs). It delves into conceptual approaches for FGM design, various manufacturing techniques, and the materials employed in their fabrication using additive manufacturing (AM) technologies. This paper explores the applications of FGMs in diverse fields, including structural engineering, automotive, biomedical engineering, soft robotics, electronics, 4D printing, and metamaterials. Critical issues and challenges associated with FGMs are meticulously analyzed, addressing concerns related to production and performance. Moreover, this paper forecasts future trends in FGM development, highlighting potential impacts on diverse industries. The concluding section summarizes key findings, emphasizing the significance of FGMs in the context of AM technologies. This review provides valuable insights to researchers, practitioners, and stakeholders, enhancing their understanding of FGMs and their role in the evolving landscape of AM