Forjamento da liga AA 2011 no estado semi-solido : estudo do processo e do produto

AUTOR(ES)

Maximino Manuel Montel Rovira

DATA DE PUBLICAÇÃO

2001

RESUMO

The work deals with the ana1ysis of the semi-solid technology applied to the thixoforming of AA 20011 aluminium alloy. Initially it was studied the influence of temperature in the quality of semi-solid raw material suitable for thixoforming (spheroidal morphology in the solid phase) when producing such material by partial melting of super-refined as-cast structures. Heat treatment at four differents temperatures (888, 893, 898 and 903 K) were carried out, to promote structure spheroidisation. Results show that perfect and equiaxial structure can be obtained in all tested conditions. Thixoforging tests at 893 K and 903 K, with maximum forces of 50, 100, 200 and 270 kN, were carried out in a specially designed die to impose severe flow conditions, in such a way that 100 % solid material would not be able to succeed. Forces were monitored during tests and their influence in the microstructure of the products was ana1ysed. Flow pattems and mechanical properties were ana1ysed. Results show that much more complex geometries can be achieved, in just one operation, when using semi-solid, globular structures. Good surface finishing and accuracy were obtained; required lower forces compared to those required for conventional forming (100 % solid) were observed when forging in the semi-solid state. Products with fine, equiaxial structure, were obtained by thixoforming. However, heterogeneous structure can be produced by liquid separation during processing. Mechanical properties of the thixoforging in the as thixoforged and after ageing treatment (T6) products were not substantially better than mechanical properties of the products obtained by conventional processes like extrusion and casting (with grain refiner). T6 treatment can improve, at certain extent, mechanical properties of the products

ASSUNTO(S)

conformação de aluminio fluidos não-newtonianos aluminio forjamento

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