A novel sandwich-structured interlayer enabled high-performance GH4169D TLP bonded joint

This work designed a new mortise structure on the to-be-welded side of TC4 titanium alloy sheet and successfully obtained MIG-welded joint of TC4 titanium alloy (TC4) to 316 L stainless steel (316 L) with high strength and toughness through the synergy of mortise structure and metallurgical bonding. The effect of mortise structure on the interfacial microstructure, mechanical properties and fracture behaviour of dissimilar joints was investigated. Various intermetallic compounds, like Ti2Cu, Ti2Cu + TiCu, and AlCu2Ti phases, formed in Ti/Cu reaction interface. The Ti/Cu interfacial layer perpendicular to the horizontal direction was generated in the mortise structure on Ti side, and the Ti-Cu phases in the inner layer of mortise sidewall evolved from coarse columnar to spherical morphology. The results showed that the mortise structure significantly improved the strength of joints. The joint with mortise structure had a maximum tensile strength of 549 MPa, which was 93.8% of the strength of the stainless steel substrate. Simultaneously, the joint with mortise structure deformed significantly before failure, and the fracture surface revealed numerous dimples on the 316 L side.

The effect of surface morphologies of Al insert, including smooth surface (SS), straight knurling (SK) and hatching knurling (HK) on interfacial microstructure, mechanical properties and fracture behaviour of Al/Mg bimetallic composites by a novel compound casting was studied in this work. The thicknesses of the interface layers of the SK-s and HK-s bimetallic composites, respectively, increased by 11.5% and 4.8% than that of the SS’s composite. The interfacial phase compositions were similar for all the bimetallic composites, mainly consisting of eutectic layer (EU) and intermetallic compound layer (IMC). Therein, the proportion of the EU layer in the entire interface layer for the SK’s and HK’s bimetallic composites was larger than that of the SS’s sample. The EU layer had a lower hardness than the IMC layer. The shear strengths of the SK’s and HK’s bimetallic composites increased by 34.2% and 50.2%, respectively, compared to that of the SS’s bimetallic composite.

Interfacial microstructure and property of 6061 aluminium alloy/stainless steel hybrid inertia friction welded joint with different steel surface roughness

Mechanical properties degradation of Sn 37Pb solder joints caused by interfacial microstructure evolution under cryogenic temperature storage

Effect of SiC nanowires addition on the interfacial microstructure and mechanical properties of the Cf-SiCNWs/AZ91D composite

The short carbon fiber reinforced 2024 Al composites were fabricated through powder metallurgy. The effect of short carbon fiber content on the interfacial microstructure and fracture behavior of the composites at different temperatures were investigated. The results showed that the dislocation accumulation was formed in the aluminum matrix due to the thermal expansion mismatch between carbon fiber and aluminum matrix. With the testing temperature increasing, the size of interfacial product Al4C3 and precipitates Al2Cu became larger, and the segregation of Al2Cu was found coarsening around Al4C3. The addition of short carbon fiber improved the hardness and modulus of the aluminum matrix in the vicinity of the interface between carbon fiber and aluminum matrix. Compared to the matrix 2024 Al, the yield strength and ultimate tensile strength of the composites first increased and then decreased with increasing short carbon fiber content at room temperature 423 Kand 523 K. The fracture surface of the composites at room temperature was characterized by shear failure of fiber, while the interface debonding and fiber pulled-out became predominant fracture morphologies for the fracture surface at increased temperatures.

The synergistic influence of cerium addition and ultrasonic vibration on the interfacial microstructures, mechanical properties and fracture behaviors of Al/Mg bimetals by compound casting

The present study highlighted the effect of alloying elements in Al alloy on the interfacial microstructure, and the corresponding fracture behaviour of the Al alloy/steel inertia friction welded joint by selectively adopting two types of Al alloys. A strong texture of <111>//radial direction was formed on the Al alloy side in both types of joints, while no obvious changes were identified on the steel side. Different types of intermetallic compounds (IMCs) were formed at the weld interface. In the Al-Mg-Si alloy/steel joint produced at a low heat input, the interfacial microstructure was composed of a nanoscale amorphous layer and partially crystallised layer, while it turned into a fully crystallised Fe2Al5 phase with Si enriched when the heat input was enhanced. In the Al-Cu alloy/steel joint, Cu was enriched at the weld interface, with the possible formation of Fe-Al-Cu based IMCs. Moreover, a two-layered structure of IMC with different compositions of Cu appeared when the joint was prepared at a high heat input. Such distinct interfacial microstructure caused different fracture behaviours of joints. An interfacial reaction layer less than 130 nm thick led to the failure of Al alloy rather than the weld interface which easily happened at a thicker IMC.

High strength diffusion bonding of Ti2AlNb to GH4169 with (TiZrHfNb)95Al5 high entropy interlayer

Effect of post weld heat treatment on the microstructure and corrosion behavior of AA2219 aluminum alloy joints welded by variable polarity tungsten inert gas welding

Auxetics and Other Systems of Anomalous Characteristics

Inhibition of interfacial reaction and enhancement of mechanical properties of CF/Al composite

Dissimilar metal welding of Q235 low carbon steel and 5052 aluminum alloy was carried out by a single/dual-beam laser in a steel-on-aluminum overlap configuration with a copper interlayer. The weld appearance, microstructure, and fracture behavior of the joints made by the single/dual-beam laser welding were investigated comparatively. The results showed that dual-beam laser welding, compared with single-beam laser welding, had better process stability which made better weld appearance and bigger effective joining width which enhanced tensile capacity. With a copper interlayer, a contact reaction zone appeared between the copper interlayer and aluminum matrix, which enlarged effective joining zone. The microstructures of the welding joint welded by a single/dual-beam laser were composed of the ligulate fusion zone with Fe-Al interface and the contact reaction brazing zone with Al-Cu interface. The Fe-Al interface mainly consisted of α-Al and Al2Cu eutectic structure, FeAl, FeAl2, and a certain amount of Al-Cu intermetallics, Fe2Al5 and FeAl3. The Al-Cu interface mainly consisted of eutectic phase Al2Cu and metastable phase of Al-Cu intermetallics. The tensile property was enhanced by a dual-beam laser, and the addition of the copper-foil interlayer might improve the metallurgical reaction of interfacial reaction region and promote the load-carrying ability of weld joint. An ideal joint with fewer defects could be obtained when the welding speed is 0.9–1.25 m/min of dual-beam laser welding and 1.5–1.75 m/min of single-beam laser welding.

The interface microstructure, mechanical properties and corrosion resistance of dissimilar joints during multipass laser welding for nuclear power plants

In order to discuss the effects of Cu-cored solder with pure Ni coating and joint height on the interfacial microstructure and mechanical properties of joints, Cu/Sn-3.0Ag0.5Cu (SAC305)/Cu and Cu/Cu-cored + SAC305/Cu sandwich solder joints were prepared using a reflow process. The interfacial microstructure of the solder joints was investigated by scanning electron microscope with energy-dispersive x-ray spectroscopy. The results showed that, at as-reflowed joints, an intermetallic compound (IMC) of scallop-like Cu6Sn5 was formed at the Cu wire/solder interface, and a plane-like (Cux, &!nbsp;Ni1−x)6Sn5 IMC was formed at the Cu core/solder interface. Compared with SAC305 solder joints, Cu-cored solder joints showed more interface layers, a thicker Cu6Sn5 IMC layer, and higher tensile strength. With increasing joint height, the thickness of the IMC at the two interfaces decreased, and the tensile strength also decreased for Cu-cored solder joints. Mixed brittle/ductile fracture appeared in SAC305 and Cu-cored solder joints with height of 600 μm, but were suppressed and transformed into ductile fractures with increasing height of the solder joints.