Evolution of microstructure, microtexture and mechanical properties of linear friction welded IMI 834

Abstract

Titanium alloys have been of great interest in the aerospace industry for many years. Recently, linear friction welding has also been making strides in conquering a part of the aerospace manufacturing market, with its clear advantages over fusion welding and mechanical fastening methods for integrated bladed rotors. High tech near-a alloy IMI834 (Ti-5?8Al-4Sn-3?5Zr-0?7Nb-0?5Mo-0?35Si) was designed to have improved creep resistance and retains its mechanical properties at temperatures up to 600uC. It balances creep resistance and fatigue strength, making it an excellent material for compressor discs and blades. IMI834 with an initial bimodal azb microstructure was welded using varying axial pressures during welding and then characterised using both microstructural examination and mechanical testing. Electron backscatter diffraction (EBSD) was used to characterise the texture and phase fraction of the welded IMI834 samples in the weld zone (WZ) and thermomechanically affected zones. The EBSD analysis revealed fine recrystallised grains at the weld centres. The microhardness evaluation of the weldments showed that the recrystallised WZ was slightly harder than the parent material (PM). The local and global tensile properties of the welds, investigated using a tensile testing rig with integrated digital image correlation, revealed higher strength in the WZ and failure in the PM.Les alliages de titane ont suscité un grand inté rê t dans l'industrie aé rospatiale pendant plusieurs anné es. Ré cemment, le soudage par friction liné aire a é galement fait de grands progrè s dans la conquê te d'une partie du marché de la fabrication aé rospatiale, avec ses avantages clairs par rapport aux mé thodes de soudage par fusion et d'assemblage mé canique pour les rotors à lames inté gré es. L'alliage de haute technologie quasi-alpha, IMI834 (Ti-5?8Al-4Sn-3?5Zr-0?7Nb-0?5Mo-0?35Si) a é té conç u pour avoir une ré sistance amé lioré e au fluage et il retient ses proprié té s mé caniques à des tempé ratures jusqu'à 600uC. Il balance la ré sistance au fluage et la ré sistance à la fatigue, ce qui en fait un excellent maté riau pour les disques et les lames de compresseur. IMI834, avec une microstructure initiale bimodale azb, a é té soudé en utilisant des pressions axiales variables lors du soudage. On l'a ensuite caracté risé en utilisant tant l'examen de la microstructure que les essais mé caniques. On a utilisé la diffraction d'é lectrons ré trodiffusé s (EBSD) pour caracté riser la texture et la fraction des phases des é chantillons soudé s d'IMI834 dans la zone de soudure (WZ) et dans les zones affecté es thermomé caniquement. L'analyse par EBSD a ré vé lé des grains fins recristallisé s au centre des soudures. L'é valuation de la microdureté des ensembles soudé s a montré que la zone de soudure recristallisé e é tait lé gè rement plus dure que le maté riau de base (PM). Les proprié té s de traction locales et globales des soudures, examiné es au moyen d'un assemblage d'essai de traction avec corré lation inté gré e d'image digita...

Strength and fatigue strength of a similar Ti‐6Al‐2Sn‐4Zr‐2Mo‐0.1Si linear friction welded joint

“…Understanding their mechanical properties in monotonic and cyclic loadings is fundamental for its industrial application. Several authors studied the tensile properties of similar LFW joints using as PM comparable alloys to Ti6242, such as TA6V and IMI‐834 . Some similar and dissimilar joints failed far from the WCZ .…”

“…Several authors studied the tensile properties of similar LFW joints using as PM comparable alloys to Ti6242, such as TA6V and IMI‐834 . Some similar and dissimilar joints failed far from the WCZ . For instance, Dalgaard et al observed that the formation of a fine microstructure in the WCZ of a similar IMI‐834 LFW joint led to a weld overmatch.…”

“…Advancements on experimental mechanics such as DIC shed new light on the strain monitoring. The assessment of the strain fields on cross‐weld specimens has already been exploited by several authors . For the last 20 years, a large number of authors have used spatio temporal graphs to highlight the presence of strain bands due to instabilities of Portevin's Le Chatelier effect and the Lüders bands.…”

High and low cycle fatigue behavior of linear friction welded Ti–6Al–4V

“…The friction between the parts generates heat, which together with the applied force results in a consolidated joint seam with a limited plastically or thermomechanically affected zone (TMAZ). Linear friction welds in titanium alloys exhibit good mechanical properties [4][5][6] as compared to other joining techniques such as laser welding [7], electron beam welding or inertia friction welding [8].…”

Microstructural Analysis of Linear Friction-Welded 718 Plus Superalloy

“…Depending on the position in the weldment, different regions of the TMAZ and the base alloy are subjected to different ranges of temperatures and plastic deformation that influence microstructural development. LFW has been successfully used to join steel 5 and titanium alloys 6,7 in applications including manufacturing and repair of turbine components. For Ni-base superalloys, LFW has been used to weld polycrystalline, This joining process is generally considered to be a completely solid-state joining process, 12 and like other friction-welding processes, it could eliminate problems associated with melting and resolidification of conventional fusion welding techniques.…”