Papers by Keyword: Bonding

Abstract: AZ91D magnesium alloy and Al metal were bonded successfully at 450 oC with load of 25 or 31 MPa by using Mg-Al eutectic alloy as the solder in atmosphere. The microstructure of the AZ91D/Al joints was characterized by SEM equipped with EDS, and the bond strength was measured through three-point bending test. It was revealed that reactive diffusion occurred obviously at the jointing part. The diffusion layers are composed of α-Mg + β-Mg17Al12, β-Mg17Al12, γ-Mg2Al3 and α-Al. The average bend strength of AZ91D/Al joints is 24 MPa with maximum value 28 MPa. To demonstrate the potential engineering application of this technology, AZ91D magnesium alloy plate was coated with Al foil and its corrosion resistance was tested. Electrochemical test results showed that the corrosion resistance of Al coated AZ91D magnesium alloy plate was greatly improved compared with the uncoated one.

Abstract: Joining nickel based superalloys to gamma-TiAl intermetallic alloys will contribute to a more efficient application of these advanced materials, particularly in extreme environments. In this study, Inconel alloy and gamma-TiAl are joined using as filler alternated nanolayer thin films deposited onto each base material. The nanolayers consisted in Ni/Al exothermic reactive multilayer thin films with periods of 5 and 14 nm deposited by d.c. magnetron sputtering in order to improve the adhesion to the substrates and to avoid the reaction between Ni and Al. Diffusion bonding experiments with multilayer coated alloys were performed under vacuum at 800°C by applying 50 MPa during 1h. Bonding was achieved in large areas of the centre of the joints where regions without cracks or pores were produced, especially when using multilayer thin films with a 14 nm modulation period.

Abstract: The optimization of CFC/Cu-interfaces for plasma facing divertor components in thermo-nuclear fusion reactors is proposed and demonstrated via an integrative numerical-experimental approach mainly comprising a macro-scale to micro-scale finite element modeling technique together with fracture mechanics tests. Results obtained by finite element analyses of real-scale CFC flat tile divertor components under high heat flux loading conditions are verified by the findings of tests in an ion beam high heat flux facility. From the macro-scale FE models of the full component the loading conditions are derived for micro-scale FE models that incorporate principal details of the micro-structured CFC/Cu-interface thus allowing to capture explicitly locally acting dissipative mechanisms which in turn at the macro-scale in fracture mechanics experiments increase the fracture toughness of the CFC/Cu-interface.

Abstract: The basic concept of an Aircraft Stuctural Integrity Program is to ensure that airframes are adequately managed to ensure safe operation without catastrophic failure, to maximise fleet availibilty and to minimise cost of ownership. In managing these three aspects, a number of conventional and advanced technologies are being adopted and applied within the RAAF. Composites and bonding technology has been developed and transitioned onto various RAAF aircraft over many years in the form of Bonded Patch Repairs to airframe structures (wing and fuselage). Based upon conventional heat treatment behaviour of aluminium alloys, Retrogressive Re-Ageing technology is being transitioned to minimise stress corrosion cracking. From structural mechanics and FEA technologies, Geometric Shape Optimisation methods have been applied to minimise peak stress thresholds within aged airframe structures. To manage structural degredation (fatigue and corrosion) a number sensor-based monitors are being developed and applied on RAAF aircraft. Finally, using the reliability methodology, a proactive management program to assess the extent of corrosion degradation within a whole aircraft is being instituted. This methodology is being articulated through a new paradigm known as “Environmental Degradation Management System – Tool Box” (EDMS-TB). Within RAAF it can be demonstrated that candidate technologies which are adopted have direct and in-direct positive influences within ASIPs to address the key structural integrity parameters of Safety, Availability and Cost of Ownership.

Abstract: We have proposed a novel bonding process using composite Ag nanoparticles composed of Ag metallo-organic nanoparticles and Ag2CO3 for an application to the assembly of electronic devices. In this research, the sintering mechanisms of the composite Ag nanoparticles are discussed based on the results of the observation of the sintering behaviors and the investigation of the thermal characteristics. Moreover, Cu specimens were bonded using the composite Ag nanoparticles for measuring the bonding strengths. Based on the results, the effects of the Ag2CO3 contents in the composite Ag nanoparticles and the bonding conditions on the bondability were evaluated. As a result, it was found that the composite Ag nanoparticles were sintered rapidly because of the interaction between the Ag metallo-organic nanoparticles and Ag2CO3. Thereby, the bondability was improved by optimizing the contents of Ag2CO3 in the composite Ag nanoparticles.

Abstract: In order to expand a market share of TiAl turbocharger a second generation TiAl turbocharger was newly developed. The characteristic of this turbocharger is its improved turbine wheel material with excellent creep strength and its low cost manufacturing processes. The usable temperature of this turbocharger is higher than Inconel713C turbocharger, and the cost is much reduced compared with current TiAl turbocharger.

Abstract: Pulsed electric current sintering (PECS) was applied to the bonding of W (tungsten) to Cu (copper) using Nb or Ni powder as an intermediate layer. The influence of the intermediate layer on the bond strength of the joint was investigated by observation of the microstructure. The bonding process was carried out at carbon-die temperatures of 1073 and 1173 K for 1.8 ks at a bonding pressure of 130 MPa. The bond strength of the joint with an intermediate layer of Ni powder was 250 MPa. This joint fractured in the Cu base during the tensile test. SEM observations of the joint with an intermediate layer of Ni revealed that a diffusion layer formed at the joint interface.

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Abstract: Robust bonding and integration technologies are critically needed for the successful implementation of silicon carbide based components and systems in a wide variety of aerospace and ground based applications. These technologies include bonding of silicon carbide to silicon carbide as well as silicon carbide to metallic systems. A diffusion bonding based approach has been utilized for joining of silicon carbide (SiC) to silicon carbide sub-elements for a micro-electro-mechanical systems lean direct injector (MEMS LDI) application. The objective is to join SiC sub-elements to from a leak-free injector that has complex internal passages for the flow and mixing of fuel and air. A previous bonding approach relied upon silica glass-based interlayers that were non-uniform and not leak free. In the newly developed joining approach, titanium foils and physically vapor deposited titanium coatings were used to form diffusion bonds between SiC materials using hot pressing. Microscopy results show the formation of well adhered diffusion bonds. Initial tests show that the bond strength is much higher than required for the component system. Benefits of the joining technology are fabrication of leak free joints with high temperature and mechanical capability.

Abstract: Application of magnesium alloy is restricted by its bad formability and low corrosion resistance. In order to resolve these problems, rolling-bonding has been tried as a new method. Pre-heating, rolling and annealing were used in the process of bonding, and aluminum cladding magnesium alloys obtained. The effects of many parameters in the processes of pre-heating, rolling and heat-treatment on bonding strength have been analyzed, and the mechanism of rolling-bonding been studied. It was found that intermediate phase played an important role in the bonding. Good bonding of aluminum cladding magnesium alloys achieved after annealing at 200oC for 1 hour.