Layered Double Hydroxide Growth on Equal Channel Angular Pressing-Processed AZ31 Alloy

The high corrosion rate of magnesium alloys in body fluids represents a serious drawback for biomedical applications. Grain refinement through of equal channel angular pressing (ECAP) processing seems to be quite promising to overcome this issue. This work investigates the conditions for depositing layered double hydroxides (LDHs) coatings through coprecipitation and hydrothermal treatment on AZ31 alloy subjected to 1, 2, and 4 ECAP passes. Owing to their tunable structure and ion-exchange capacity, LDHs have the capability to load and release drugs. Synthesis is made by using two distinct synthesis times (30 min and 12 h) and then the samples are examined by light microscopy, scanning electron microscopy, and X-ray diffraction. The results show that LDH deposition is strongly affected by the substrate microstructure. LDH nucleation occurs on screw dislocations emerging at the surface of substrate: fine and homogeneous distribution of LDH crystals is achieved if, in addition to homogeneous nuclei distribution, surface diffusion occurs. This condition is favored by the 0002-texture component. The deposition on AZ31 alloy subjected to 1 ECAP pass with a synthesis time of 30 min gives rise to a complete surface coating and a crystal morphology that seems suitable for medical and biomedical applications.