Evolution of mechanical properties and room temperature corrosion resistance of Mg-3Nd and Mg-3Y alloys processed by equal channel angular pressing

Abstract

A single addition of the rare earth elements neodymium and yttrium have been made to magnesium alloys Mg-3Nd and Mg-3Y. Both alloys were proceeded by hot extrusion and equal channel angular pressing (ECAP) for up to 8 passes using route BC in order to investigate the microstructure evolution, work hardening processes and room temperature corrosion resistance.

The initial as-extruded grained structure of 20μm was effectively refined down to a sub-micrometer scale of an average grain size of ~ 600nm after 8 passes through ECAP. The refining effect of ECAP was more intensive in the case of Mg-3Y.

At the same time, further ECAP process leads to massive precipitation and fragmentation of intermetallic particles only in the Mg-3Nd alloy. Whereas in the alloy Mg-3Y distinct smaller volume fraction of equilibrium βe particles was observed.

The grain refinement with a combination of precipitation in the case of Mg-3Nd and solid solution hardening in the case of Mg-3Y strengthened alloys. The mechanical properties were detected by microhardness tests which increased up to 30% at 8 passes in both alloys, compared to the initial extruded condition.

The presence of the intermetallic phases in the magnesium matrix had an accelerating effect during the initial corrosion attackin the case of Mg-3Nd. However, in the case of Mg-3Y significant increase of corrosion resistance with the increasing number of ECAP passes was measured.