Dissimilar friction welding of 6061-T6 aluminum and AISI 1018 steel: Properties and microstructural characterization

The joining of a 6-mm thickness Al 6061 to AISI 1018 steel has been performed by the combined effects of fusion and solid state welding. The process is derived from friction stir welding (FSW) but with an adjustable offset of the probe location with respect to the butt line. Metallographic studies by optical microscopy, electron probe microscopy, and the utilization of the X-ray diffraction technique have been conducted. It was found that the intermetallic phases Al13Fe4 and Al5Fe2 exist in the weld zone. The tool was significantly worn during welding and is broken after traveling 100 mm at a rotational speed of 917 rpm. The wear of the tool significantly affects the structure of the weld, and the tool breakage was detected by the incorporated acoustic emission (AE) sensors. It appears that the joining of an Al 6061 alloy to AISI 1018 steel with a sound heterogeneous weld microstructure is feasible using this process, and the tool breakage can be detected by the AE sensing technique.

Joining of Al 6061 alloy to AISI 1018 steel by combined effects of fusion and solid state welding

Interfacial reaction in steel–aluminum joints made by friction stir welding

Dissimilar metal friction welding of austenitic–ferritic stainless steels

Friction welding (FW) is a high quality, nominally solid-state joining process, which produces welds of high structural integrity. Rotary friction welding (RFW) is the most commonly used form of FW, while linear friction welding (LFW) is a relatively new method being used mainly for the production of integrally bladed disc (blisk) assemblies in the aircraft engine industry. Numerous similar and dissimilar joints of structural metallic materials have been welded with RFW and LFW. In this review, the current state of understanding and development of RFW and LFW is presented. Particular emphasis is placed on the process parameters, joint microstructure, residual stresses, mechanical properties and their relationships. Finally, opportunities for further research and development of the RFW and LFW processes are identified.

Linear and rotary friction welding review

Type 5052 aluminium alloy was joined to type 304 austenitic stainless steel via a continuous drive friction welding process. The joint strength increased, and then decreased after reaching a maximum value, with increasing friction time. Joint strength depended on the size and shape of the tensile testpiece. Friction weldability could be estimated by electrical resistmetry. The process of friction welding between the aluminium alloy and the stainless steel is proposed to evolve as follows: welding progresses from the outer to the inner region; an unbonded region is retained at the centre of the weld interface with shorter friction time; longer friction time causes the formation of an intermetallic reaction layer at the weld interface; and the reaction layer grows as the friction time increases. When the thickness of the reaction layer increased above a critical value, the joint was brittle and fractured at the weld interface. The joint was sound when there was no unbonded region and a thin reaction...

Friction welding process of 5052 aluminium alloy to 304 stainless steel

Amorphization by friction welding between 5052 aluminum alloy and 304 stainless steel

A type 1050 commercial aluminium was bonded to a type 304 austenitic stainless steel using a continuous drive friction welding process. The bonding interface conditions were evaluated by means of mechanical tests, to measure tensile and bending properties, and ultrasound microscopic observation. The tensile strength of the joints increased as the frictional time increased. High strength joints could be obtained at a frictional time greater than 0.2 s. However, ultrasound microscopy clearly showed that bonding progress occurred from the peripheral region towards the centre of the faying surface and, furthermore, that the frictional time of 0.2 s was not sufficient for complete bonding and much more frictional time was necessary. It is thus difficult to exactly evaluate the joint strength of a soft-hard metal combination by tensile and bending tests alone. Therefore, ultrasound microscopic observation together with mechanical testing is recommended as a convenient method to evaluate such a joint.

Evaluation of friction weld interface of aluminium to austenitic stainless steel joint

Type 1050 aluminium was bonded to type 304 stainless steel by a friction welding procedure. The aluminium was greatly deformed, and the grains were elongated and refined near the weld interface. The stainless steel was slightly deformed and partly transformed at the faying surface from austenite to martensite owing to hard friction. As a result, the hardness of both materials in the vicinity of the weld interface was higher than that of the base metals. Constituent elements of both materials had interdiffused through the weld interface, and some intermetal1ic compounds, Fe2Al5, FeAl, and Fe3Al, were formed at the weld interface. It was presumed by estimating with metallographic observation that the welding temperature was lower than the lowest eutectic temperature in the metal system. So the friction welding mechanism of this system was based on interdiffusion of each constituent in the solid state.

Microstructure of friction weld interface of 1050 aluminium to austenitic stainless steel

The microstructures of commercial purity aluminium near the friction weld interface were observed by transmission electron microscopy. Large plastic deformation of aluminium occurred near the weld interface and the microstructure of the aluminium was oriented from the centre to the periphery of the weld nugget. The aluminium grains were refined, and there were many recrystallised grains which were almost dislocation free. The refined grains, which were of size ~ 1 νm, formed very near the weld interface. The grain boundary was estimated to be a large angle tilt boundary. The refined grains were mainly formed by dynamic recrystallisation during the upset stage of the welding cycle. A large amount of shear strain and heat were introduced during the friction stage, and dynamic recrystallisation started during the upset stage. Grain growth occurred during air cooling after the upset stage. The grain size was larger in the central region than in the periphery owing to the variation in temperature. The...

T. Tomita

Papers

Friction welding process of 5052 aluminium alloy to 304 stainless steel

Amorphization by friction welding between 5052 aluminum alloy and 304 stainless steel

Evaluation of friction weld interface of aluminium to austenitic stainless steel joint

Microstructure of friction weld interface of 1050 aluminium to austenitic stainless steel

Dynamic recrystallisation phenomena of commercial purity aluminium during friction welding