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Friction stir based welding and processing technologies - processes, parameters, microstructures and applications: A review

Twenty-year uninterrupted endeavor of friction stir processing by focusing on copper and its alloys

Wire arc additive manufacturing is currently rising as the main focus of research groups around the world. This is directly visible in the huge number of new papers published in recent years concerning a lot of different topics. This review is intended to give a proper summary of the international state of research in the area of wire arc additive manufacturing. The addressed topics in this review include but are not limited to materials (e.g., steels, aluminum, copper and titanium), the processes and methods of WAAM, process surveillance and the path planning and modeling of WAAM. The consolidation of the findings of various authors into a unified picture is a core aspect of this review. Furthermore, it intends to identify areas in which work is missing and how different topics can be synergetically combined. A critical evaluation of the presented research with a focus on commonly known mechanisms in welding research and without a focus on additive manufacturing will complete the review.

The Current State of Research of Wire Arc Additive Manufacturing (WAAM): A Review

In the present study, friction stir processing (FSP) is used for the synthesis of an aluminum metal matrix composite (MMC) reinforced by SiC particles. MMC specimens with reinforced microstructures exhibited significant improvement in hardness (near 50%). Isothermal uniaxial tensile tests were employed for the as-received, friction stir processed and composite microstructures at ambient and high temperatures under strain rates ranging from 10−2 to 10−4 s−1 to investigate the effect of deformation rate on the mechanical behavior. At ambient temperature, notable improvement of the yield strength was observed reaching about 240% of the as-received samples while the ductility was reduced near to 4%. Elevated temperature flow curves were perceptibly sensitive to strain rate, especially for FSPed and MMC samples. Fracture surface observations hinted at the distribution of second phase particles along with possible damage mechanisms.

High temperature characteristics of Al2024/SiC metal matrix composite fabricated by friction stir processing

Friction stir channeling (FSC) is a simple method for fabrication of a continuous, integral channel in a monolithic plate, which is carried out in a single pass. The fabricated channels can be applied in heat exchanger industry. In this study, a novel technique was introduced to produce channels in 6061 aluminum alloy which is named as Modified Friction Stir Channeling (MFSC). This technique is derived from Friction stir processing. In this technique, the tool profile and position of tool pin against work piece were designed differently from FSC process. Channels were fabricated with a very regular shape such as rectangular. Comparison between MFSC and FSC showed that fabricated channels, using MFSC process, had better properties relative to fabricated channels by FSC.

Modified Friction Stir Channeling: A Novel Technique for Fabrication of Friction Stir Channel

Effects of microstructural evolution on the corrosion properties of AISI 420 martensitic stainless steel during cold rolling process

Effect of interpass temperature on the formation of retained austenite in a wire arc additive manufactured ER420 martensitic stainless steel

In this study, microstructural features and mechanical properties of a wire arc additively manufactured 420 martensitic stainless steel were investigated in as-printed and heat-treated conditions. Initial microstructural investigations on the as-printed part revealed the formation of residual δ-ferrite during the solidification process, which is known as a deleterious phase to both mechanical and corrosion performance of stainless steels. To remove the residual δ-ferrite and obtain a fully martensitic microstructure, the as-printed samples were subjected to different austenitizing temperatures of 950, 1050, 1150, and 1300 °C. Austenitizing at 1150 °C was selected as the optimum cycle due to removal of undesirable phases, such as δ-ferrite and carbides, resulting in a fully martensitic microstructure. Following the austenitizing heat treatment, the samples were tempered at different temperatures including 200, 300, 400, 500, and 600 °C. Increasing the tempering temperature was found to vary the size, morphology, and distribution of chromium carbides precipitated during the tempering process. Although, tempering at lower temperatures (200 and 300 °C) decreased the hardness due to the formation of tempered martensite and stress relieving of the structure, the intermediate temperature of 400 °C increased the hardness value by virtue of the formation of carbides at optimum size and distribution. However, tempering at 500 and 600 °C decreased the hardness as compared to 400 °C due to intergranular segregation and coarsening of carbides. The results of uniaxial tensile testing were consistent with the hardness measurements and confirmed that the tempering temperature of 400 °C led to the optimal combination of strength and ductility ascribed to the formation of fine and homogenously distributed chromium carbides embedded in a moderately tempered martensitic matrix.

Effects of post-printing heat treatment on the microstructure and mechanical properties of a wire arc additive manufactured 420 martensitic stainless steel part

Modified friction stir channeling (MFSC) is a new approach for fabrication of a continuous, integral channel in monolithic Al plate, which is carried out in a single pass. This technique is derived from Friction Stir Processing (FSP). Tool profile and position of tool pin against work piece were designed differently from conventional Friction Stir Channeling (FSC) process. In MFSC, Fabricated channel with more regular shape than FSC process shows that the channel formation mechanism is different from FSC. So, in this study, in order to understand the formation of channel, material flow in MFSC is investigated using weakened tool pin technique. Moreover, one of the most important channel properties is width of channel. This characteristic affected the channel area and shape of the channel. Width of channel was unknown in FSC process. But in MFSC, a new region is investigated which determines the channel width.

Salar Salahi

Papers

Modified Friction Stir Channeling: A Novel Technique for Fabrication of Friction Stir Channel

Effects of microstructural evolution on the corrosion properties of AISI 420 martensitic stainless steel during cold rolling process

Effect of interpass temperature on the formation of retained austenite in a wire arc additive manufactured ER420 martensitic stainless steel

Effects of post-printing heat treatment on the microstructure and mechanical properties of a wire arc additive manufactured 420 martensitic stainless steel part

Channel Formation in Modified Friction Stir Channeling