Compound Behavior Between Reinforcement And Braze Metal Research On Semisolid Stirring Brazing

This paper study the compound behavior between reinforcement and braze metalunder the semi-solid stirring brazing which is based on1st stirring brazing that use fluxlessand non-vacuum semisolid process to join SiCp/A356aluminum matrix composites withZn73Al27filler metal. The brazing mechanical performance was tested by electronic typeuniversal test machine (WD.100KE), microstructure of brazing joint and elementdistribution in the interface was analyzed by State smart digital universal opticalmicroscope (XJP-6A), SEM, EDX and EPMA. The compound behavior betweenreinforcement and braze metal under the semi-solid stirring brazing was discussed.The results show that2nd stirring brazing which based on1st semi-solid stirringbrazing continues to heat up, and explores the influence on the welded joint structure of2nd stirring brazing which is affected by process parameters (2nd brazing temperature,stirrer diameter, stirrer rotating speed). As rising of II times temperature, base metal existsa certain width dissolved layer, the joint has influence on stirrer diameter: as stirrerdiameter increases, brazing seam organization by branches crystal becomes sphericalCrystal, SiC particles into brazing seam by less to more, and wetting braze metal, thenformed composite brazing seam which improves mechanical performance of brazing seam,but as rising temperature and increasing stirrer diameter, the void of brazing seam alsoincreased, therefore research was did under II times stirring brazing with large stirrer ofdifferent rotating speed at the high temperature. The results found that forming quality ofparticles enhanced reinforcement and braze metal composite could be improved at lowrotating speed in II times stirring brazing, while stirring with suitable diameter, brazingseam interface and center of brazing seam had high mechanical performance, for65r/minsecondary stirring brazing with2.4mm diameter stirrer in530℃, shear strength of thecentre joint is236.5MPa, shear strength of brazed seam interfacial is212.25MPa.Study the compound behavior between SiC particles and braze metal based onexperimental. It can be found that as stirring speed increased, SiC particle of dissolutionbase metal progressively entered into the brazing seam process using fixed-point stirringtest, and established the compound behavior between SiC particles and braze metal at2ndstirring brazing on a trial basis. In the initial state, under dissolved materials without force,there was no SiC particles in the braze joint. In the early stirring, dissolved material has partial liquefaction phenomenon, there are mutual diffusion of elements, forming a liquidphase channel, dissolving the SiC particles can be migrated to the braze joints under thestirring action, while braze joints metal diffusion spread to the base metal, it can be foundthat the metal to fill the stirrer around. In the stirring medium, SiC particles of dissolvinglayers mixed with braze metal further while dissolved materials in the stirring force withthe increase stirring speed. At the same time, SiC particle of base metal dissolution wasreducing, forming a composite seam while migrated to the braze joints. Later in the stirring,SiC particles of dissolving layers mixed with braze metal more uniform, the oval shapewas showed around the stir-welding head while filled with alloy, forming a full of SiCparticle reinforced composite SiC particle reinforcement and braze metal.