In Situ Intermetallics-Reinforced Composite Prepared Using Multi-Pass Friction Stir Processing of Copper Powder on a Ti6Al4V Alloy

Abstract

Multi-pass friction stir processing (FSP) was used to obtain a titanium alloy/copper hybrid composite layer by intermixing copper powder with a Ti6Al4V alloy. A macrostructurally inhomogeneous stir zone was obtained with both its top and middle parts composed of fine dynamically recrystallized α- and b-Ti grains, as well as coarse intermetallic compounds (IMCs) of Ti2Cu and TiCu2, respectively. Some b grains experienced β → α a decomposition with the formation of acicular α-Ti microstructures either inside the former b-Ti grains or at their grain boundaries. Both types of β → α a decomposition were especially clearly manifested in the vicinity of the Ti2Cu grains, i.e., in the copper-lean regions. The middle part of the stir zone additionally contained large dislocation-free b-Ti grains that resulted from static recrystallization. Spinodal decomposition, as well as solid-state amorphization of copper-rich b-Ti grains, were discovered. The FSPed stir zone possessed hardness that was enhanced by 25% as compared to that of the base metal, as well as higher strength, ductility, and wear resistance than those obtained using four-pass FSPed Ti6Al4V.

Friction Stir Welding/Processing of Various Metals with Working Tools of Different Materials and Its Peculiarities for Titanium Alloys: A Review

“…Under the conditions of friction stir processing or welding, a number of structural and phase changes of processed materials occur, caused by processes occurring in different areas along the contour of the tool [127,260,287]. Such processes may include mutual dissolution of system components with the formation of supersaturated solid solutions or intermetallic phases, occurring during intense plastic deformation under conditions of elevated temperature [105,127].…”

“…Such processes may include mutual dissolution of system components with the formation of supersaturated solid solutions or intermetallic phases, occurring during intense plastic deformation under conditions of elevated temperature [105,127]. Another basic process is the decomposition of supersaturated solid solutions with the formation of particles of secondary intermetallic phases in the stir zone behind the tool at a gradual decrease in temperature [260,287].…”

“…The formation of a heterogeneous gradient structure during processing or welding depends significantly on the melting temperature of the components, their mutual solubility, the phases formed in the contact zone, the ratio of the components, as well as the rotational speed of the tool, the loading force, and the longitudinal speed [260,287]. These processes are further complicated by inhomogeneities of plastic deformation, grain refinement, and material flow, as well as by non-uniform temperature distribution at different distances from the tool [288,289].…”

“…Currently, friction stir welding of titanium alloys is intensively investigated, as evidenced by a rather large number of papers in the literature [17,[82][83][84][85][86]268,278,340,341,. In the field of friction stir welding of titanium alloys, the research is less intensive [81,106,287,313,357,[376][377][378][379][380][381][382].…”

Macro- and Microstructure of In Situ Composites Prepared by Friction Stir Processing of AA5056 Admixed with Copper Powders

“…Friction stir processing and intermixing SiC particles loaded into holes drilled in a Ti-6Al-4V alloy plate resulted in a nearly twofold increase in microhardness and wear resistance [ 7 ]. The multipass FSP intermixing of copper powder into Ti-6Al-4V allowed fabricating an in-situ composite reinforced both by Ti 2 Cu particles and spinodal decomposition, that demonstrated reduced wear and friction [ 8 ]. The magnesium matrix composite Al-Ti-TiC-CNTs/AZ31 was prepared using the high-speed (3000 RPM, 1000 mm/min) FSP on a coating made of mechanically alloyed and laser pre-sintered Al-Ti-TiC-CNTs powder composition, demonstrated the presence of the intermetallic particles Al 12 Mg 17 and TiC, which enhanced both hardness and corrosion resistance [ 9 ].…”