Laser-assisted friction stir processing of IN738LC nickel-based superalloy: stir zone characteristics

Friction stir processing (FSP) of high softening-temperature materials such as nickel-based superalloys is considered to be difficult. Laser heating of a localised area ahead of the FSP tool was used to provide sufficient plasticity during the FSP of IN738LC nickel-based superalloy. The stir zone (SZ) microstructure of the friction stir processed and laser-assisted friction stir processed were characterised. Laser-assisted friction stir processing (LAFSP) produced a defect-free pass, but FSP resulted in generation of a discontinuity in the SZ. Both lower volume fraction of partially dissolved γ′ precipitates and coarser grain structure of SZ in LAFSP led to more ductility of the SZ material and elimination of the defects.     

Projection friction stir spot welding: a pathway to produce strong keyhole-free welds

ABSTRACT

This paper introduces a novel facile method, called projection friction stir spot welding, to produce a keyhole-free friction stir welds based on a pinless tool method involving using a specially designed projection on the surface of the backing anvil. The projection plays two key roles contributing to the bonding mechanism and the joint strength: (i) encouraging the material flow perpendicular to the joint interface and (ii) bending the joint interface at the edge of the projection. The process enables pathway to produce keyhole-free welds with superior mechanical performance in steel sheets compared to the other spot welding techniques.     

Wire-Based Friction Stir Processing as a Novel Pathway for Solid-State Surface Alloying of Magnesium

Wire-based friction stir processing is introduced as a solid-state surface alloying strategy for surface alloying of AZ31 magnesium alloy with aluminum, as a key alloying element in magnesium alloys. This technique enables the formation of a defect-free, grain refined and alloyed surface with the increased volume fraction of Mg-Al second phase, and thus, enhanced surface hardness. This simple technique provides a solid-state surface alloying pathway to improve the surface properties of the metallic materials.