Abstract
This paper studies the weld interface microstructure and mechanical properties of AlMg6-stainless steel and AlMg6-titanium bimetals produced using explosive welding. The microhardness (HV), tear strength, and microstructure of the weld seams were evaluated. The interface of the weld zones had a flat profile. No structural disturbances or heterogeneity in the AlMg6-titanium weld interface were observed. On the other hand, the bimetal AlMg6-stainless steel had extensive zones of cast inclusions in the 10–30 µm range. SEM/energy-dispersive X-ray spectroscopy (EDS) analysis showed the presence of a hard and brittle intermetallic compound of Al and FeAl3 (with 770–800 HV). The microhardness of the AlMg6-titanium bimetal grew higher closer to the weld interface and reached 207 HV (for AlMg6) and 340 HV (for titanium). Both bimetals had average tear strength below 100 MPa. However, the tear strength of some specimens reached 186 and 154 MPa for AlMg6-titanium and AlMg6-stainless steel, respectively. It is also worth mentioning that heat treatment at 200 °C for one hour led to a uniform distribution of tear strength along the entire length of the bimetals. The study shows that one of the possible solutions to the problem of the formation of the brittle intermetallic compounds would be the use of intermediate layers of refractory metals.
Highlights
Aluminum and its alloys are widely used in marine construction and offshore structures [1].The use of aluminum alloys makes it possible to reduce the weight of various constructions [2,3].At present, bimetallic transition joints are used, which allow welding aluminum alloy parts and superstructures to the hulls of ships, railway wagons, or fuselages of aircraft [4]
These problems are mainly caused by the formation of brittle Fex Aly intermetallic compounds at the weld interface [6,7,8], the difference in the melting points of the two metals and their oxides, the difference in their physical properties, dissimilar thermal expansion, etc
The explosive welding (EW) of titanium to aluminum and aluminum alloys poses a number of problems caused by the formation of Al3 Ti and AlTi intermetallic compounds, the metastable phases of Al5 Ti3, amorphous structures, and solid solutions along the weld interface [22,23]
Summary
Aluminum and its alloys are widely used in marine construction and offshore structures [1]. The tear strength values of the seams lie within the 80–120 MPa range These interlayers are widely used both in EW and in rolling of metals and alloys that form brittle intermetallic compounds. EW causes the plastic deformation of the metal parts and the heating of the contact surfaces [19] This produces local pockets of intermetallic compounds, which during further heat treatment or fusion welding can grow several times in size and have a negative impact on the strength of the bimetal. The EW of titanium to aluminum and aluminum alloys poses a number of problems caused by the formation of Al3 Ti and AlTi intermetallic compounds, the metastable phases of Al5 Ti3 , amorphous structures, and solid solutions along the weld interface [22,23]. The results obtained in the paper serve as the basis for further studies in the field
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