of the original manuscript:Vaidya, W.V.; Horstmann, M.; Ventzke, V.; Petrovski, B.; Kocak, M.; Kocik, R.; Tempus, G.: AbstractDissimilar welds of aluminium alloy AA6056 and titanium alloy Ti6Al4V were produced by a novel technique. AA6056 sheet was machined at one end to a U-slot shape, enabling the intake of the Ti6Al4V sheet. The Al-alloy U-slot was then butt welded by split laser beam without using a filling wire, thus making a weld by melting only the Al-alloy.Thereby the intermetallic brittle phase TiAl 3 formed at the weld interface and affected mechanical properties. As a continuation of the previous work, the joint design was modified by chamfering Ti6Al4V to reduce the formation of interfacial TiAl 3 . It is shown in this work how this seemingly insignificant joint modification has refined microstructure and increased hardness and strength. The most impressive feature was the improved resistance to fatigue crack propagation whereby the fracture type in the fusion zone of AA6056 adjacent to the weld interface changed from partially intercrystalline to completely transcrystalline. Possible metallurgical processes leading to the property improvements are discussed.

The experimental programme of the EC supported project (SMT 2070) SOTA aimed at addressing a technical and industrial need to provide guidelines for creep crack growth (CCG) testing and data analysis of weldments. Mechanical and creep properties were determined on two pressure vessel steels of P22 (2.25Cr1Mo) and P91 (9Cr1MoVNb). The specimens were taken from pipe welds for weld metal (WM) tests, and simulated heat affected zone (HAZ) material for the HAZ tests. Creep crack growth (CCG) tests were carried out on cross-weld compact tension (CT) specimens machined out from weldment of pipes. The tests were done at 550 °C and 600 °C on P22 and P91 materials, respectively. The CT specimens were notched using electrical discharge method (EDM), for a sharp starter crack. This method of initiating sharp starter crack was chosen to make sure that all partners will test specimens with starter crack location as specified in the work programme to study crack initiation and growth in WM, HAZ (both in the centre and type IV region). The CCG tests were carried out following the ASTM E1457-92 [Ref.1]. The partners assessed their data and sent both assessed and their raw data to be further assessed centrally. All the data from partners were analysed and compared with those of partners' own assessed data. The present paper reports on the analyses of CCG data obtained in the programme including six laboratories from six European countries. The programme addresses the differences and difficulties in testing and the assessment of weldments, and provides guidelines for harmonisation of testing procedures for reliable data production for remanent life assessment of plants with welded components.

Sheets of AA6056 and Ti6Al4V were butt-joined by inserting the Ti-sheet into the profiled Al-sheet and by melting the Al-alloy alone using a split beam Nd:YAG laser.To study microstructural effects on properties, the Al-alloy was used in two tempers; T4followed by post weld heat treatment T6, and in T6 followed by a defined duration of natural ageing at room temperature. As a basic step for fatigue and fracture investigations, local gradients in properties of this dissimilar joint are investigated using microscopy, hardness and tensile tests. Possible sites, from which fracture may initiate, have been then identified. All property changes are found to confine to the aluminiumside. An intermetallic layer, although very thin, is found to form on the interface. The changeovers, firstly between the fusion zone and the heat affected zone and secondly between the heat affected zone and the base material, are found to be associated with changes in microstructure, hardness and strength. These are identified as the possible critical sites in addition to the interface. Fig. 1 to follow) for further weight saving and economy, since a specific material can be chosen for a specific local requirement. However, dissimilar welds are a metallurgical challenge [4]. Local gradients in microstructure, chemistry and properties become inherent and need to be accounted for in design.Moreover, when a non-ferrous partner is involved, intermetallic phases formed tend to be brittle [4] and consequently properties of the weld are impaired. Residual stresses [5] at the interface and in the partners may complicate the matter further.With weight alone as the criterion, three base metals become interesting on the density basis; magnesium, aluminium and titanium. Magnesium is, however, yet to find acceptance for wide aerospace applications and so only Al-and Ti-alloys become relevant for dissimilar joints. Some physical properties collected from the literature [6] are shown in In the following, the terminology "welding" [25] has been retained, since at least one partner was melted (and thus it is not considered as brazing). The partners are also referred to synonymously by the respective side, e.g., AA6056 as the Al-side.Moreover, specimens from the laboratory coupons (and not the component in Fig. 1c) have been tested. Experimental procedureSheets of the precipitation hardenable AlMgSiCu type alloy, AA6056 (uniform thickness 2 mm) and Ti6Al4V (thickness 1.8 mm; mill annealed) were welded to coupons as shown in Figs. 1a,b using a split beam 4 kW Nd:YAG laser in the heat conduction mode at BIAS in Bremen, Germany, without using filler wire. The coupon had the dimensions 330 x 94 mm 2 . To study the effect of starting microstructure on properties two tempers were selected for AA6056:• welding in T4 followed by artificial ageing T6 (190 °C-4h/air); denoted also as "T4/T6" or "T4 followed by post weld heat treatment T6", and• welding in T6 and naturally aged (at least for 7 weeks) without any further artificial ageing; denoted also as "T6...

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High temperature deformation and crack resistance of low alloy ferritic grade P22 steel weldments applied in power plants are reported. The creep crack initiation (CCI) and creep crack growth (CCG) data were determined using compact type (C(T)) and C-Shape (CS(T)) fracture mechanics specimens at 550 °C. The deformation and crack growth behaviour of similar weldment zones and significance of CCI and CCG in defect assessment of components were addressed. The weldments with industrially relevant properties were produced in butt welded pipe joint from which test specimens are sampled. The studied material covers a spectrum of microstructures and ductility over the weldment zones to give representative for a welded component. The emphasis is placed on the measurement and particularly analysis of crack initiation for failure assessment in P22 steel weldments. The particular importance of construction of isochronous curves for time dependent failure assessment diagram (TDFAD) method is reported. It is aimed to contribute establishing guidelines for acceptable methodologies for testing, analysis and assessment of welded components using TDFAD for high temperature service.