The effects of postweld heat treatment (PWHT) on 3.2-mm-and 5.1-mm-thick Ti-6Al-4V butt joints welded using a continuous wave (CW) 4-kW Nd:YAG laser welding machine were investigated in terms of microstructural transformations, welding defects, and hardness, as well as global and local tensile properties. Two postweld heat treatments, i.e., stress-relief annealing (SRA) and solution heat treatment followed by aging (STA), were performed and the weld qualities were compared with the as-welded condition. A digital image correlation technique was used to determine the global tensile behavior for the transverse welding samples. The local tensile properties including yield strength and maximum strain were determined, for the first time, for the laser-welded Ti-6Al-4V. The mechanical properties, including hardness and the global and local tensile properties, were correlated to the microstructure and defects in the as-welded, SRA, and STA conditions.
The mechanical properties and microstructural evolution of WASPALOY joined by linear friction welding (LFW) were investigated in this study. In-situ temperature measurements using thermocouple probes indicated exposure of the weld area to a temperature of at least 1400 K (1126°C). Based on electron backscatter diffraction (EBSD) mapping of the weldments, up to 50 pct reduction in c grain size occurred within 0.9 mm of the weld interface as a result of dynamic recrystallization (DRX). Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) studies revealed that progressive dissolution of c¢ precipitates took place from the base metal to the weld interface, where almost no c¢ precipitates were observed. Within 3.3 mm of the weld interface, the c¢ dissolution significantly influenced the hardness profile measured across the extended thermomechanically affected zones (TMAZs). Investigation of strain distributions during tensile testing using the optical Aramis system revealed weak bonding at the edge of the weld due to oxidation. To extrude out oxide layers into the flash, increasing the axial shortening to higher than 1.2 mm is recommended.
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...
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