a) Resultados experimentais para a deformação do nióbio demonstram a eficiente do projeto da matriz ECAP para o refinamento microestrutural em matrizes de 90° e 120°.
b) Amostras de nióbio foram deformadas por ECAP, nas matrizes de 90° e 120°, de 1 a 14 passes, e não apresentaram trincas e fissuras;
c) O processo de deformação ECAP apresentou eficiência no refino da microestrutura logo na primeira passagem, em boa parte da amostra deformada para as matrizes de 90° e 120°, com severidade mais acentuada para a matriz de 90°;
d) O estado estacionário de refinamento para o ângulo de 120° ocorreu em 8 passes e para o ângulo de 90° esse estágio foi observado em 6 passes. O estado estacionário depende do nível de deformação e como a matriz de 90° apresenta maior severidade, o estado estacionário foi observado em menor número de passes;
e) O estado estacionário de refinamento nas matrizes de 90° e 120°, analisados do ponto de vista da microestrutura, apresenta em ambos os casos, cristalitos em toda a amostra, e ausência de bandas de cisalhamento e zonas mortas;
f) Houve aumento significativo dos valores de dureza com o aumento do número de passes (1 – 14) em ambas as matrizes;
g) Na matriz de 120° com 14 passes, não foi obtida uma microestrutura formada de grãos equiaxiais direcionadas no sentido de extrusão, enquanto na matriz de 90°, entre 12 e 14 passes, foi observado o direcionamento de cristalitos;
h) A importância dos dados experimentais ECAP obtidos com nióbio validaram as matrizes projetadas e a variáveis de processo analisadas e as variáveis experimentais produziram informações que possibilitaram a realização de um novo projeto de matrizes. Os dados levantados estão sendo utilizados nesse momento no projeto de duas novas matrizes.
SUGESTÕES DE TRABALHOS FUTUROS
a) Realizar os ensaios de tração para avaliar a resistência à tração de materiais deformados por ECAP;
b) Mensurar os tamanhos de contornos de grãos com o aumento do número de passes;
c) Avaliar o efeito do número de passes na resistência à corrosão da liga por meio de técnicas de ensaios eletroquímicos;
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