CORRELATION OF THERMAL, TENSILE AND CORROSION PARAMETERS OF ZN-AL ALLOYS WITH COLUMNAR, EQUIAXED AND TRANSITION STRUCTURES

摘要

The columnar to equiaxed transition (CET) has been examined in different wrought and casting alloys for many years and the metallurgical significance of CET has been treated in several articles. Experimental observations in the literature have focused on thermal parameters like cooling rate, velocity of the liquidus and solidus fronts, local solidification time, temperature gradients and recalescence. The objective of the present research consist on studying the influence of solidification thermal parameters on the type of structure (columnar, equiaxial or with the CET) and on the secondary dendritic spacing in Zn-Al alloys (Zn-1%A1 and Zn-4wt%Al, weight percent). Also, correlate the thermal and structural parameters of these alloys with tensile and corrosion behavior. The results show that Zn-4wt%Al alloys are more resistant to the corrosion that Zn-lwt%Al, independently of the structure. Also, in both alloys the equiaxed structures presented a better tensile resistance than the columnar and CET zones.