Effect of Er and Zr on Hot Crack Resistance and Mechanical Properties of Al-Cu-Mn-Cd alloy

This work discusses the characterization of the hot cracking resistance and mechanical properties of Al-Cu-Mn-Cd (-Er-Zr) alloy using the "constrained rod casting" method and mechanical tensile testing. Analysis of the Al-Cu-Mn-Cd (-Er-Zr) alloy's microstructure was conducted using testing methods such as optical microscopy, scanning electron microscopy, transmission electron microscopy, and others. The results indicate that alloys with the addition of Er and Zr exhibit higher resistance to hot cracking compared to alloys without Er and Zr. The Er and Zr mainly refine the grain size by increasing the degree of ingredient supercooling, while simultaneously improving the alloy's resistance to hot cracking by increasing the proportion of eutectic structure. The addition of Er and Zr results in grain size refinement and a reduction in the secondary dendrite arm spacing. The average grain sizes of alloys containing Er and Zr, and alloys without Er and Zr, are 138.43 mu m and 151 mu m, respectively. The average spacing of secondary dendrite arms is 21 mu m and 31 mu m, respectively. The average tensile strengths of alloys treated with T6 heat treatment are 500 MPa and 474 MPa, respectively. During the heat treatment process of the alloy containing Er and Zr, the formation of the Al3(Er, Zr) phase provides non-uniform nucleation sites for the theta ' phase, thereby reducing the size of the theta ' phase and consequently enhancing the strength of the alloy.