Fatigue Behavior of Laser-Cut Sheet Metal Parts with Brazed-on Elements

Laser cutting is used in the production of formed sheet metal components. However, the cyclic load capacity is reduced compared to other subtractive processes. Laser cutting results in a significant loss of fatigue strength; however, thermal joining has its own effect on the cyclic load capacity. Accordingly, brazing causes a significant reduction in the mechanical strength. However, the open question is what consequences a combination of both processes may have on the overall fatigue strength of sheet metals. Laser-cut samples of AISI 304 with and without a brazed-on element were investigated for their microstructure and mechanical properties. The brazing process was found to have an annealing effect on the microstructure. It was further observed that the fatigue behavior of brazed specimens is dominated by inhomogeneities at the surface of the filler metal fillet located in the geometric notch of the brazed joint. Fatigue strength decreased by almost 50% compared to as-cut specimens. As long as no shared diffusion zone is formed between the laser-cut and the brazed joint, the use of laser cutting for the production of such components appears to be reasonable and does not further contribute to the loss of cyclic strength.

Gas brazing of thin-sheet galvanized steel with aluminum solders

. In this work, the first stage of experimental research was carried out to estimate the main physicochemical processes that determine the qualitative characteristics of a brazed joint made of thin sheet galvanized steel during gas brazing with aluminum solder systems. In particular, an estimation was made of the ability of spreading and wetting of aluminum solders (AlSi5, AlSi12) on the surface of thin sheet galvanized steel ( DX56D + Z of 0.4 mm thick and zinc-coated layer of 45–65 microns) at a step-by-step increase in the heating area of the base metal in the presence and absence of flux (Al-Flux 726). The aluminum alloys was heated “not directly,” but through the base metal to maximize the preservation of the anticorrosive zinc coating at the interface between the liquid solder and the base material.

Brazing of Porous Copper Foam with Copper Sheet Using CuNiSnP Amorphous Filler Metal

This research studies effects of the brazing time on interfacial microstructure of brazed joint between the porous copper foam (PCF) and Cu substrate using CuNiSnP amorphous filler metal. To examine the interfacial microstructure and its properties, an assessment of PCF/CuNiSnP/Cu brazed joints was conducted after electric furnace brazing under hydrogen (H2) atmosphere. The results showed that the interfacial microstructure was thick for short brazing time specimens and thin for prolonged brazing time specimens. The interfacial microstructures consisted of Cu-rich solid solution, (Cu, Ni)3P, and Cu3P as a eutectic structure discovered in the brazing region at different brazing times of 5, 10, and 20 min. Only the Cu-rich solid solution and (Cu, Ni)3P were found in the specimen with brazing time of 30 min. indicating that different brazing times affected interfacial microstructures and therefore reliability of the brazed joints.

Microstructure and Physical Properties of Alloy Brazed with Filler by Mapping Scanning Analysis and Wettability Test

In this paper, a new type of AlSiMgCuNiAg filler metal was developed. The solidus temperature of the filler metal is 509.1°C and the liquidus temperature is 531.3°C. The filler metal has a good wetting and spreading effect on the surface of 6061 aluminum alloy. The CuAl2 phase in the brazing seam was greatly aggregated after brazed, while the CuAl2 phase was reduced and Mg2Si strengthening phase was formed when the brazed joints with heat treatment. The average shear strength of the brazed joint without heat treatment was 47.1MPa, and the average shear strength of the brazed joint with heat treatment reached to 108.7Mpa. The strength of the brazed joint with heat treatment was increased by about 131% relative to the strength of the brazed joint without heat treatment.

Dissimilar Brazing of Ti–15Mo–5Zr–3Al and Commercially Pure Titanium Using Ti–Cu–Ni Foil

Dissimilar brazing of Ti–15Mo–5Zr–3Al (Ti-1553) to commercially pure titanium (CP-Ti) using Ti–15Cu–15Ni foil was performed in this work. The microstructures in different sites of the brazed joint showed distinct morphologies, which resulted from the distributions of Mo, Cu, and Ni. In the brazed zone adhered to the Ti-1553 substrate, the partitioning of Mo from the Ti-1553 into the molten braze caused the formation of stabilized β-Ti without Ti2Cu/Ti2Ni precipitates. In the CP-Ti side, the brazed joint displayed a predominantly lamellar structure, composed of the elongated primary α-Ti and β-transformed eutectoid. The decrease in the Mo concentration in the brazed zone caused the eutectoid transformation of β-Ti to Ti2Cu + α-Ti in that zone. The diffusion of Cu and Ni from the molten braze into the CP-Ti accounted for the precipitation of Ti2Cu/Ti2Ni in the transformed zone therein. The variation in the shear strength of the joints was related to the amount and distribution of brittle Ti2Ni compounds. Prolonging the brazing time, the wider transformed zone, consisting of coarse elongated CP-Ti interspersed with sparse Ti2Ni precipitates, was responsible for the improved shear strength of the joint.

Study on the Residual Stress Relieving Mechanism of C/C Composite-Nb Brazed Joint by Employing a Structurally Optimized Graphene Reinforced Cu Foam Interlayer

Cu foam has previously been investigated and verified to be an excellent interlayer candidate for relieving high residual stress within C/C composite-Nb brazed joints. However, the optimized geometric structure of Cu foam for brazing has never been properly investigated since it was always employed as a reactant for acquiring homogeneous distribution of the interfacial structures in the brazed joints. In this work, graphene reinforced Cu foam composite (G-Cuf) interlayers were used for brazing C/C composite and Nb. Through the protection effect of graphene on the Cu foam substrate, the impact of porosity and thickness of a structurally intact Cu foam on the joint structure and properties were investigated by finite elemental analysis as well as through experimental studies. By introducing a G-Cuf interlayer with an optimized porosity of 90% and thickness of 0.15 mm, the shear strength of the C/C composite-Nb brazed joint reached 45 MPa, which is 3.5 times higher than that of the joint brazed directly without an interlayer. The strain energy of the brazed joint assisted by G-Cuf interlayer reduced from as high as 10.98 × 10–6 J to 6.90 × 10–6 J, suggesting that the residual stress was effectively mitigated.

Effect of In and Pr on the Microstructure and Properties of Low-Silver Filler Metal

The novel low-silver 12AgCuZnSn filler metals containing In and Pr were used for flame brazing of copper and 304 stainless steel in this study. The effects of In and Pr content on the melting temperature, wettability, mechanical properties and microstructure of 12AgCuZnSn filler metal were analyzed. The results indicate that the solidus and liquidus temperatures of filler metals decrease with the addition of In. Trace amounts of Pr have little impact on the melting temperature of the low-silver filler metals. In addition, the spreading area of filler metals on copper and 304 stainless steel is improved. The highest shear strength of brazed joint is 427 MPa when the content of In and Pr are 2 wt.% and 0.15 wt.%, respectively. Moreover, it is observed that the trace amount of Pr significantly refines the microstructure of brazed joint matrix. A bright Pr3Cu4Sn4 phase is found in filler metal and brazing seam when the contents of In and Pr are 5 wt.% and 0.5 wt.%, respectively.