s moradnezhad - M.Sc. Student of Imam Khomeini International University Qazvin, Iran
a razaghian - PhD. Imam Khomeini International University Qazvin, Iran,
m emamy - PhD. School of Metallurgy and Materials, College of Engineering, University of Tehran, Tehran, Iran,
r taghiabadi - PhD. Imam Khomeini International University Qazvin, Iran

This research work has been carried out to study the effect of different Ca contents (0.5, 1.0, 1.5, 2.0 and 3.0) on the microstructure and porosity content of ZK60 alloys. The samples were examined by the use of optical and scanning electron microscopy (SEM) to evaluate the modification efficiency of the alloy with different Ca concentrations. The cast specimens have been modified, homogenized and extruded at 350 °C at an extrusion ratio of 12:1. Experimental results showed that the addition of Ca brings about precipitation of a new phases and refines the as-cast grains. It was also found that the presence of Ca at higher concentrations (> 2 wt. %) results in the formation of hard Ca-rich intermetallics segregated in cell boundaries. Hot-extrusion was found to be powerful in breaking the eutectic network and changing the size and morphology of Ca-rich intermetallics phase. By applying the extrusion process and increasing the Ca concentration (up to 2.0 wt. %) porosity percentage decreased from 13.62% to 6.34% and 7.11% to 3.89% for ZK60 and ZK60+3%Ca alloys, respectively.

ZK60 alloy, Porosity, Ca addition, extrusion