Ti-6Al-4V alloy with two kinds of open cellular structures of stochastic foam and reticulated mesh was fabricated by additive manufacturing (AM) using electron beam melting (EBM), and microstructure and mechanical properties of these samples with high porosity in the range of 62%∼92% were investigated. Optical observations found that the cell struts and ligaments consist of primary α' martensite. These cellular structures have comparable compressive strength (4∼113 MPa) and elastic modulus (0.2∼6.3 GPa) to those of trabecular and cortical bone. The regular mesh structures exhibit higher specific strength than other reported metallic foams under the condition of identical specific stiffness. During the compression, these EBM samples have a brittle response and undergo catastrophic failure after forming crush band at their peak loading. These bands have identical angle of ∼45° with compression axis for the regular reticulated meshes and such failure phenomenon was explained by considering the cell structure. Relative strength and density follow a linear relation as described by the well-known Gibson-Ashby model but its exponential factor is ∼2.2, which is relative higher than the idea value of 1.5 derived from the model.

Compression deformation behavior of Ti-6Al-4V alloy with cellular structures fabricated by electron beam melting

Effect of a copper filler metal on the microstructure and mechanical properties of electron beam welded titanium–stainless steel joint

High strength electron beam welded titanium–stainless steel joint with V/Cu based composite filler metals

Microstructure and tensile properties of laser beam welded Ti–22Al–27Nb alloys

Laser welding was applied to join 2.5 mm thick dissimilar metals of Ti–22Al–27Nb (at%) alloy and TC4 (Ti–6Al–4V, wt%) alloy. The microstructure characterization and the mechanical properties of the laser welded joints were investigated. The results show that a well-quality joint can be obtained using laser welding method. The B2 phase and a little residual coarse α2 phase are formed in heat affected zone (HAZ) of Ti–22Al–27Nb alloy. The heat affected zone of TC4 alloy mainly consists of a mixture of martensitic α′, acicular α, and primary α phase. The weld metal is mainly composed of B2 phase and martensitic α′ phase. The microhardness values of heat affected zone are higher than that of fusion zone (FZ) and the base metal. And the fusion zone exhibits the lowest microhardness values in the welded joint. The average tensile strength of the joints can reach about 92% of the TC4 parent metal, but the elongation of the joints is found to be less than 40% of the TC4 parent metal.

Microstructure and mechanical properties of laser welded Ti–22Al–27Nb/TC4 dissimilar alloys

Dissimilar weld joints in Ti3Al/TC4 were welded using the electron beam (EB) process. The microstructure evolution characterizations of the joints was investigated by means of OM, SEM, XRD, TEM and the tensile strengths of the joints were tested. The microstructure of the weld metal of every joint was identical. The structures were characterized by martensite, appearing coarse equiaxed grains. There existed grain coarsening and martensitic transformation in Ti3Al/HAZ and TC4/HAZ. With the increase of heat input, the grain size was significantly raised, yet the composition of the weld metal was independent of heat input. The highest tensile strength of the joints can reach 831 MPa, equaled almost to 92% of that of Ti3Al-based alloy.

Interfacial microstructure and strength of the dissimilar joint Ti3Al/TC4 welded by the electron beam process

An electronic beam welding method of Ti-Al alloy by adding transmission layer to generate intermetallic compound includes thermally treating the Ti-Al alloy to be welded for eliminating stress, chemically and physically cleaning the surfaces of TiAl alloy and metallic foil, filling the metallic foil in the seam to be welded, preheating by electronic beam, microalloying by electronic beam, and natural cooling.

Huiqiang Wu

Papers

Interfacial microstructure and strength of the dissimilar joint Ti3Al/TC4 welded by the electron beam process

Electron beam welding method of adding transition layer into compound between metals of titanium aluminium alloy