Microstructure characterization of vacuum Brasing of metal-ceramic junctions of h-BN with Mo metal and Kovar alloy

• Grant number: 17/10464-5
• Support type: Scholarships in Brazil - Scientific Initiation
• Effective date (Start): October 01, 2017
• Effective date (End): July 31, 2018
• Field of knowledge: Engineering - Materials and Metallurgical Engineering
• Principal Investigator: Conrado Ramos Moreira Afonso
• Grantee: José Francisco Caldeira Maranho
• Home Institution: Centro de Ciências Exatas e de Tecnologia (CCET). Universidade Federal de São Carlos (UFSCAR). São Carlos , SP, Brazil
• Associated research grant: 13/05987-8 - Processing and characterization of amorphous, metastable and nano-structured metallic alloys, AP.TEM

Abstract

Actually, in addition to the high cost of using Ag as an alloying element, Ti acts as an activating element to promote interface reactions in the region of the brazing joint in commercial addition alloys, i.e. Ticusil® (Ag-Cu-4,5Ti). Technologically, it is necessary to produce brazed joints of h-BN/Kovar and h-BN/Mo in laboratory scale for the mechanical and microstructural characterization, in order to compare the performance of the alloys produced currently with the commercial alloy. The amorphous alloys are basically formed in deep eutectics, more precisely in near-eutectic compositions, in multicomponent alloys (3 or more elements). Recently, glass forming alloys such as the Cu-Zr and Ni-Nb binary systems have shown the formation of bulk metallic glasses (BMG) with diameter, Ø = 1 mm (copper mold cast cylinders). The glassy alloys exhibit Tg before the crystallization temperature, Tx (K), forming the supercooled liquid interval, DTx = Tx - Tg, which the larger the tendency to form a glassy phase, TFV (GFA - "Glass forming ability", and through cooling rates of 1 to 103 K / s. The first objective of this work is to develop a new route for the manufacture of addition alloys for brazing using alloy amorphization of the Cu-Zr and Ni-Nb binary systems, which contribute to increase the surface wettability of h-BN during the brazing process As an alternative to the use of commercial alloys of the Ag-Cu eutectic system. The characterization techniques used in this work will be X-ray diffraction (XRD), thermal analysis (DSC), scanning (SEM) and transmission electron microscopy (TEM) coupled to energy dispersive spectroscopy (EDS). Vicker microhardness measurements will be done as well along the tracks. This research will also be associated to a Thematic Project (Nº: 2013 / 05987-8) and PIPE FAPESP 2015/50110-2 which is responsible for the Laboratory of Amorphous and Nanocrystalline Alloys. (AU)