Filler metal

About: Filler metal is a research topic. Over the lifetime, 11152 publications have been published within this topic receiving 86590 citations.

Effect of welding speed on microstructural and mechanical properties of laser lap weld joints in dissimilar Al and Cu sheets

Abstract: Conventional fusion welding of aluminium and copper dissimilar materials is difficult because of poor weldability arising from the formation of brittle intermetallic compounds on the weld zone as well as different chemical, mechanical and thermal properties of welded joints. Joining of Al and Cu plates or sheets offers a metallurgical challenge due to unavoidable formation of brittle intermetallic compounds. Therefore, it is necessary to effectively suppress the formation and growth of Al–Cu intermetallic compounds. For welding of dissimilar Al and Cu sheets, no systematic work has been conducted to reduce these defects. Thus, this paper focuses on the effect of welding speed on the quality of a lap weld joint in the Al and Cu sheets with a single mode fibre laser. It was found that consequently sound strong weld joints could be produced by suppressing the formation of intermetallic compounds in the interface zone at extremely high speeds.

Active brazing carbon/carbon composite to TC4 with Cu and Mo composite interlayers

Abstract: Active filler metal (TiZrNiCu) was used to increase the wettability and Cu and Mo composite interlayers were added to release residual stress and increase the mechanical properties of TC4–C/C composite joints The mechanical properties of the brazed joints were measured by shear strength testing The effects of brazing parameters on the microstructures of the brazed joint were investigated by SEM, EDS and XRD It is shown that the maximum shear strength of the joints is 21 MPa brazed at 900 °C for 5 min, which is about 3 times greater than brazing alloy alone When the brazing temperature is low, the interface structure of C/C composite/Cu brazed joint is Cu/Cu 51 Zr 14 /Ti 2 (Cu,Ni) + Ti(Cu,Ni) + TiCu + Cu 2 TiZr/(Ti,Zr)C/C/C composite With the increased brazing temperature, Ti 2 (Cu,Ni), Ti(Cu,Ni), TiCu and Cu 2 TiZr reaction phases disappear Cu(ss) and Ti(Cu,Ni) 2 appear The thicknesses of Cu 51 Zr 14 and (Ti,Zr)C reaction layers increase When the brazing temperature is high, the interface structure change to Cu/Cu 51 Zr 14 /Cu(ss) + Ti(Cu,Ni) 2 /(Ti,Zr)C/C/C composite

The Mechanism of Ductility Dip Cracking in Nickel-Chromium Alloys : Subsolidus cracking results from global stresses produced during fusion welding and local stresses generated when coherent or partially coherent second phases form

Abstract: High-chromium (-30 wt-%) nickel-alloy filler metals are desirable for use in nuclear power systems due to their outstanding resistance to corrosion and stress corrosion cracking. However, these alloys are susceptible to welding defects, especially to subsolidus intergranular cracking commonly known as ductility dip cracking (DDC). In order to develop a high-chromium filler metal that is resistant to as-welded defects, a series of Ni-Cr alloys between 16 wt-% and 34 wt-% chromium were assessed for their susceptibility to cracking. Each alloy was evaluated by fabricating a restrained, multipass, automatic gas tungsten arc, V-groove weld, and counting the number of cracks per unit area observable at 50x. The type of cracking (subsolidus DDC or solidification cracking) was further differentiated via scanning electron microscopy. The results from these welds, coupled with microstructural characterization, chemical analyses, mechanical testing, microstructural modeling, and finite element modeling indicate that DDC in Ni-Cr alloys is caused by the combination of macroscopic thermal and solidification stresses induced during welding and local grain boundary stresses generated during precipitation of partially coherent (Cr,Fe) 23 C 6 carbides. Cracking can be mitigated by alloying to minimize (Cr,Fe) 23 C 6 precipitation (e.g., by Nb and Ti additions), lessening the misfit between the matrix and these precipitates (lowering the Cr and Fe concentration), and by minimizing welding-induced stresses. This mechanism of precipitation-induced cracking (PIC) via misfit stresses is consistent with subsolidus cracking in other alloy systems including superalloys, nickel-copper alloys, titanium alloys, and ferritic steels where ductility loss corresponds to the time/temperature regime where partially coherent or fully coherent second phases form.