Oxidation Behavior of Three Different Zones of Linear Friction Welded Ti₂AlNb Alloy

Abstract

Linear friction welding is employed to weld a Ti2AlNb-based alloy. The oxidation behavior of three different zones, i.e., base metal, weld zone, and thermo-mechanically affected zone is studied at 800 C exposed to air. The oxidation kinetics of the specimens consist of an initial parabolic kinetic and followed by a linear kinetic. For the base metal, absorption of more oxygen due to higher amount of a 2 phase leads to the thickest oxidation scale, while the preferential formation of Al 2 O 3 for the joint contributes to better oxidation resistance. The presence of AlNbO 4 for all the three zones can be observed after a prolong exposure in air, leading to a drastic acceleration of oxidation rate.

Hot corrosion behavior of three different zones of linear friction welded Ti‐22Al‐25Nb alloy

“…Corrosion products formed on the surface are mainly composed of NaNbO 3 and TiO 2 . As compared to oxidation behavior of Ti 2 AlNb alloy, the chemical activity of Nb is more active in mixed molten salt, which is detrimental to the corosion resistance.…”

“…Thus, the continuous Al 2 O 3 layer cannot be formed in the base metal, which is beneficial for the formation of pitting corrosion. For LFWed Ti 2 AlNb joint, recrystallized fine grains obtained at high temperature can provide more diffusive channels than that of the base metal. High‐speed diffusive channels for short‐circuit diffusion of alloy elements offered by grain boundaries can promote the selective oxidation, which is supposed to contribute to the formation of the protective Al 2 O 3 layer .…”

“…Actually, micro‐segregation, phase transformation, dynamic recrystallization, and grain coarsening during welding may deteriorate the corrosion resistance of the joint . According to our previous research, the microstructure of LFWed joint changed drastically under thermo‐mechanical coupling effects during welding process, as a result, the LFWed Ti 2 AlNb joint exhibits different oxidation behavior compared to its base metal …”

“…Until now, researches about LFW mainly focus on welding procedure tests, microstructure evolution, numerical modeling during welding, thermo‐mechanical coupling analysis, and single chip microcomputer control, whereas few reports have been found on corrosion behavior of LFWed joint . Corrosion of weldment will affect the operation of equipment and lead to great economic loss.…”

Intergrowth Bonding Mechanism and Mechanical Property of Linear Friction Welded Dissimilar Near‐Alpha to Near‐Beta Titanium Alloy Joint

“…[4] According to the reports by Vairis and Frost, [5][6][7] the LFW process is divided into four stages: being the initial, transition, equilibrium (quasisteady friction stage), and deceleration. To date, many materials have been successfully joined with LFW, such as titanium alloys, [8][9][10][11][12][13] superalloys, [3,[14][15][16][17][18][19] steels, [20][21][22][23] and aluminum alloys, [24][25][26][27] where titanium alloys take up a great proportion.…”