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Publication
Ligação heterogénea de titânio e magnésio por friction stir spot welding
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Abstract(s)
Friction Stir Spot Welding (FSSW) oferece novas oportunidades para unir materiais diferentes, como ligas de Magnésio a ligas de Titânio. A produção destas ligações permite a combinação da baixa densidade do Magnésio com a resistência específica e a resistência à corrosão do Titânio. Trata-se de uma combinação inovadora e pouco explorada na literatura, mas que pode revolucionar determinados setores industriais, através do aparecimento de soluções de Engenharia especialmente disruptivas. Neste sentido, o presente trabalho teve por objetivo produzir e caracterizar morfológica, microestrutural e mecanicamente soldaduras heterogéneas de Titânio e Magnésio por FSSW. Testaram-se diferentes valores de velocidade de rotação, profundidade de penetração e tempo de soldadura. Para o efeito, foi utilizada microscopia ótica, microscopia eletrónica de varrimento, espectroscopia por dispersão de energia, ensaios de dureza e ensaios de tração-corte. Este processo permitiu unir ligas de Mg e Ti, usando o Mg como chapa superior, com o objetivo de minimizar o desgaste da ferramenta. Todas as ligações apresentaram semelhanças na sua morfologia global, apesar das várias condições testadas. Todos os parâmetros testados tiveram grande impacto nas temperaturas e na sua evolução ao longo do processo. Por sua vez, a velocidade de rotação apresentou o maior impacto nas condições de soldadura, sendo o principal responsável pela união, ou não, dos materiais. Para velocidades de rotação de 870 rpm, não houve união. Relativamente à macro e microestrutura das ligações, a união dos materiais não se processou através do estabelecimento de mecanismos de macro e microancoragem, o que se deveu, seguramente, à geometria da ferramenta e à diferença nas propriedades mecânicas dos materiais. As ligações bem sucedidas apresentaram resultados de resistência muito promissores. Verificou-se que as ligações produzidas com maior velocidade de rotação e tempo de soldadura apresentam maior resistência mecânica, o que resulta da maior largura de ligação na interface.
Abstract Friction Stir Spot Welding (FSSW) offers new opportunities for joining different materials, such as magnesium alloys to titanium alloys. The production of these joints allows the low density of magnesium to be combined with the specific strength and corrosion resistance of titanium. This is an innovative combination that has been little explored in the literature, but which could revolutionise certain industrial sectors, through the emergence of particularly disruptive engineering solutions. The aim of this study was to produce and morphologically, microstructurally and mechanically characterise dissimilar Titanium-Magnesium FSS welds. Different values of rotation speed, penetration depth and welding time were tested. Optical microscopy, scanning electron microscopy, energy dispersive spectroscopy, hardness tests and tensile shear tests were used to analyse the welds. This process made it possible to join Mg and Ti alloys, using Mg as the top plate, with the aim of minimising tool wear. All the welds showed similarities in their overall morphology, despite the various conditions tested. All the parameters tested had a major impact on the temperatures and their evolution throughout the process. In turn, the rotation speed had the greatest impact on the welding conditions, being the main factor responsible for the joining or not of the materials. For rotation speeds of 870 rpm, there was no bonding. With regard to the macro and microstructure of the joints, the materials were not joined through the establishment of macro and micro interlocking mechanisms, which was certainly due to the geometry of the tool and the difference in the mechanical properties of the materials. The successful joints showed very promising strength results. It was found that the joints produced with a higher rotation speed and welding time have greater mechanical strength, which results from the greater bonding width at the interface.
Abstract Friction Stir Spot Welding (FSSW) offers new opportunities for joining different materials, such as magnesium alloys to titanium alloys. The production of these joints allows the low density of magnesium to be combined with the specific strength and corrosion resistance of titanium. This is an innovative combination that has been little explored in the literature, but which could revolutionise certain industrial sectors, through the emergence of particularly disruptive engineering solutions. The aim of this study was to produce and morphologically, microstructurally and mechanically characterise dissimilar Titanium-Magnesium FSS welds. Different values of rotation speed, penetration depth and welding time were tested. Optical microscopy, scanning electron microscopy, energy dispersive spectroscopy, hardness tests and tensile shear tests were used to analyse the welds. This process made it possible to join Mg and Ti alloys, using Mg as the top plate, with the aim of minimising tool wear. All the welds showed similarities in their overall morphology, despite the various conditions tested. All the parameters tested had a major impact on the temperatures and their evolution throughout the process. In turn, the rotation speed had the greatest impact on the welding conditions, being the main factor responsible for the joining or not of the materials. For rotation speeds of 870 rpm, there was no bonding. With regard to the macro and microstructure of the joints, the materials were not joined through the establishment of macro and micro interlocking mechanisms, which was certainly due to the geometry of the tool and the difference in the mechanical properties of the materials. The successful joints showed very promising strength results. It was found that the joints produced with a higher rotation speed and welding time have greater mechanical strength, which results from the greater bonding width at the interface.
Description
Dissertação para obtenção do grau de Mestre em Engenharia Mecânica, na Área de Especialização de Manutenção e Produção
Keywords
Friction stir spot welding Magnésio Titânio Interface Junta dissimilar Magnesium Titanium Dissimilar joint
Citation
VIEIRA, António José de Melo e Castro – Ligação heterogénea de titânio e magnésio por friction stir spot welding. Lisboa: Instituto Superior de Engenharia de Lisboa. 2024. Dissertação de Mestrado.