Correlation between thermal parameters, structures,dendritic spacing and corrosion behavior of Zn–Al alloys with columnar to equiaxed transition

A.E. ARES; L.M. GASSA; S.F. GUEIJMAN ; C. E. SCHVEZOV

JOURNAL OF CRYSTAL GROWTH

Elsevier

Lugar: Amsterdan; Año: 2008 vol. 310 p. 1351 - 1361

0022-0248

The columnar to equiaxed transition (CET) has been examined for many years and the significance of CET has been treated in severalarticles. Experimental observations in different alloy systems have shown that the position of the transition is dependent on parameterslike cooling rate, velocity of the liquidus and solidus fronts, local solidification time, temperature gradients and recalescence. Thedendritic structure in alloys results in microsegregation of solute species which affects significantly the mechanical properties of thematerial. The main parameters characterizing the microstructure and the length range of microsegregation is the spacing which isclassified as primary, secondary and tertiary. Properties like mechanical resistance and ductility are influenced by the dimensions andcontinuity of the primary branches, while the secondary and tertiary branches permit the isolation of interdendritic phases which candeteriorate the mechanical behavior of the material. Since the morphology and dimensions of the dendritic structure is related to thesolidification parameters mentioned above, for each type of alloy it is essential to correlate dimensions and solidification conditions inorder to control the structure. The objective of the present research consists on studying the influence of solidification thermal parameterswith the type of structure (columnar, equiaxial or with the CET); and with grain size and dendritic spacing (primary and secondary) inZn–Al (ZA) alloys (Zn—4 wt%Al, Zn—16 wt%Al and Zn—27 wt%Al, weight percent). Also, correlate the thermal parameters, type ofstructure, grain size and dendritic spacing with the corrosion resistance of these alloys.