Papers by Keyword: Brazing

Abstract: This study aims to identify the effects caused by diffusion through heat treatment in diamonds, brazed components with metals and its effects on mechanical properties and microstructure. It will be used diamond films produced by CVD process, brazed by active filler metals with metallic substrate, using a high vacuum furnace at MAT / LNLS / CNPEM; the samples were heat treated in the atmosphere furnace at MAT too. The characterizations are carried out by hardness testing, vacuum sealing equipment at the MAT / LNLS / CNPEM facilities, and chemical and microstructural characterization will be performed using the scanning electron microscopes and EDS at LNNano / CNPEM.

Abstract: Microstructure evolution of a 3003 sheet cladded with 4004 brazing alloy is investigated during slow heating (1K/min) under secondary vacuum up to isothermal brazing temperature (590°C). Optical and scanning microscopies, EDS chemical analysis and EBSD orientation mapping are used. Experimental results are discussed in the light of thermodynamic calculations using Thermo-Calc. Comparisons show good agreement as long as Mg vaporization does not take place.

Abstract: This study focuses on understanding the effect of Ni and Co additions to filler metals on Ag-brazed joints of cemented carbide and martensitic stainless steel. Ni and Co added braze alloys were processed based on Ag-Cu-Zn ternary alloy, and joint strength and microstructure of the brazed layer has been investigated. The joint strength increased by the 2.0mass%Ni and 0.5mass%Co addition into braze alloy. This trend is remarkable in the Co added alloy, and the brazed joint increased by 141% compared to that in no-added alloy. The joint strength was closely related to the suppression effect of Co dissolution from cemented carbide into filler layer and Fe diffusion from the stainless steel to the brazed layer. In the brazed microstructure, Co-depleted zone caused by dissolution of Co in the cemented carbide was observed near the interface between the cemented carbide and the steel. Width of the Co-depleted zone significantly decreased in the Co added alloy. However, the joint strength decreased in the multiple addition compared to that in the single addition of Ni or Co.

Abstract: Present heat exchangers should ensure very good heat transfer while having as small size, high durability and the optimum performance at low prices. Thus to achieve these goals is used as base material, aluminum in various forms, of which can be made the heat exchangers energetic efficient. Realization of aluminum heat exchangers can be properly with present requirements using the brazing joint elements. Brazing achieved joining with temperature for two base materials using a filler metal with a melting point above 450°C. A properly brazed joint is performed with a metallurgical connection between two or more metals, which is generally as strong as or stronger than the base metal used.

Abstract: In this paper we propose to analyze drawing of bimetallic sheets joined by brazing. Drawing is the transformation of a plan workpiece to the drawn part or workpiece transformation with decreasing of depth corresponding transverse dimensions. The brazing process is based on the difference in the melting points of the base materials and filler metal. During the brazing process, the bimetallic sheets to be assembled are heated for at a temperature between the melting temperatures of the two alloys, this process tends to modify the geometry and the microstructure of the brazed sheets.

Abstract: Cu-Sn-Ti filler alloy was applied as brazing material to join UcBN grains onto the steel matrix using three different brazing temperatures (880, 900 and 920°C). The microstructure and properties of the UcBN-filler-steel joint and the compressive strength of UcBN grains were investigated respectively by means of scanning electron microscopy and energy dispersive X-ray spectroscopy and compressive test. The microstructural studies revealed an intermetallic interlayer of type TiN, TiB and TiB₂ at the joint interface, which grew with increasing brazing temperatures. The compressive force of UcBN grains with a maximum value of 79.3N was found when the brazing temperature was 900°C for 8 min. The wear process of brazed UcBN grains was a process transforming from abrasion wear to micro fracture mutually.

Abstract: The reaction process between Ti₂AlC and Ag-Cu filler alloy was mentioned in our previous study. However, the reaction mechanism between Ti₂AlC and filler alloy remained uncertain due to the existence of TiAl₂, which was widely distributed in the dual-phase Ti₂AlC substrate and exhibited intense reaction with Cu. In current research, pure-phase Ti₂AlC was brazed to Cu using Ag-Cu filler alloy respectively at 850°C and 900°C for 10 min. First of all, to investigate the influence of TiAl₂ on clarifying the reaction mechanism, Ti₂AlC substrates with different component (single phase and dual phase) were joined to Cu at 850°C for comparison. However, in these joints, it was difficult to find any other reactant except for AlCu₂Ti. Thus, the pure-phase Ti₂AlC was brazed to Cu at 900°C, aiming to intensify the interaction between substrates and filler alloy. For characterizing the microstructure evolution in the joint, the typical region of the joint that contained all the reactants was selected and sliced by focused ion beam technology. Combining with transmission electron microscopy, all the decomposition products (e.g. Ti₃AlC₂ and TiC) in the joint were identified. Then the decomposition mechanism of Ti₂AlC was clearly disclosed.

Abstract: In the present study, Cu-Sn-Ti filler alloy with different content of Sn was used to join Ti₂AlC ceramic and copper at 950 °C for 10 minutes. Effect of Sn content on the microstructure, mechanical property and electrical conductivity of the joints were investigated.The results indicate that the joint was comprised of five parts: copper substrate/ diffusion area in the copper substrate (Cu [Al, S solid solutions)/ brazing layer (Cu [Al, S+CuSn₃Ti₅)/ interaction area in the Ti₂AlC substrate (Ti₂AlC+ Cu [A+AlCu₂Ti+TiC)/ Ti₂AlC ceramic substrate.With the content of Sn element in the joint increasing, the filler alloy performed lower melting point and better fluidity during brazing. Thus partial filler alloy flowed out of the brazing seam, leading to the reduction of CuSn₃Ti₅ phases. Simultaneously, more Ti and Al diffused toward the Cu substrate, where a line of AlCu₂Ti phases was formed. The maximum shear strength 158.5 MPa was obtained by using Cu80Sn10Ti10 (at.%) filler alloy, at which the joint strength was 71% of that of the Ti₂AlC ceramic. The joint strength was deteriorated while the higher content of Sn was incorporated (>10 at.%), which was caused by the weak interfacial bonding between the substrates and the brazing layer. Besides, the electrical conductivity was decreased from 5.65×10⁶ s/m to 4.99×10⁶ s/m with increasing Sn content in the filler alloy.

Abstract: C/SiC composite and TC4 alloy were successfully brazed using 70Ag28Cu2Ti (wt. %) as filler metal at 820 °C~920 °C for 5 min ~30 min. The effects of brazing parameters on the microstructures, phase composition, shear strength of the brazed joints were investigated by SEM, XRD. The mechanical performances of the brazed joints were measured by a universal mechanical testing machine. The results show that successful joining of C/SiC composite and TC4 alloy owes to interfacial reactions between the brazing alloy and the parent materials, and resultantly produce TiC, Ti5Si3 and Ti-Cu serial compounds at the interfaces; the interfacial structure of the brazed joint is C/SiC composite / TiC / Ti5Si3 /Ag (s.s) +Cu (s.s) / TiCu2 / Ti3Cu4 / TiCu / Ti2Cu / TC4 from C/SiC composite side to TC4 alloy side; the maximum shear strength of the brazed joint is 53.3 MPa at 860°C for 10min.

Abstract: In order to achieve the composite of the AZ91 magnesium alloy and pure aluminum sheet, Zn-Sn-Al solder as compound agent, electric arc plating was employed to spray the brazing solder on the surface of AZ91 and pure Al sheets. The sheets were then subjected to heat treatment at 420 for 10min before rolling lamination at a reduction of 10%. The as-rolled sheets were annealed at 390 for 4hours. The microstructure, phase constitution and bonding strength of the composite interface were tested and analyzed by using SEM and energy dispersive scope (EDS), x-ray diffraction and tensile test. Experimental results showed that, under the atmospheric environment, AZ91/Al composite can be successfully fabricated with Zn-Sn-Al solder by brazing and hot-rolling, and the shearing strength can reach 22.46MPa. After annealing for 4 hours, a diffusion layer composed mainly of Al and Zn elements was formed near Al matrix, and the intermetallic phases were MgZn₂ and Mg₂Sn which was the same to the phases at the interface of AZ91/Al composite without annealing, but the amount was relatively higher. The interfacial fracture of composite was mainly due to the existence of intermetallic phases.