Controlling Corrosion Resistance of a Biodegradable Mg–Y–Zn Alloy with LPSO Phases via Multi-pass ECAP Process

Abstract

Mg-RE (rear earth) alloys with long period stacking (LPSO) structures have great potential in biomedical applications. The present work focused on the microstructure and corrosion behaviors of Mg 98.5 Y 1 Zn 0.5 alloys with 18R LPSO structure after equal channel angular pressing (ECAP). The results showed that the ECAP process changed the grain size and the distribution of LPSO particles thus controlled the total corrosion rates of Mg 98.5 Y 1 Zn 0.5 alloys. During the ECAP process from 0p to 12p, the grain size reduced from 160-180 μm (as-cast) to 6-8 μm (12p). The LPSO structures became kinked (4p), then started to be broken into smaller pieces (8p), and at last comminuted to fine particles and redistributed uniformly inside the matrix (12p). The improvement in the corrosion resistance for ECAP samples was obtained from 0p to 8p, with the corrosion rate reduced from 3.24 mm/year (0p) to 2.35 mm/year (8p) in simulated body fluid, and the 12p ECAP alloy exhibited the highest corrosion rate of 4.54 mm/year.

Recent Advances in the Equal Channel Angular Pressing of Metallic Materials

“…However, for Mg alloys, it is difficult to refine the grain size to submicron grains with the increase of the pass. Wang et al showed that the grain size decreased from 160-180 µm to 6-8 µm after twelve passes at 380 • C for Mg alloys with long-period stacking structure [61], Jiang et al reported that ultrafine equiaxed grains of 2.5 µm were obtained after sixteen passes via route A at 603 K [62]. Ma et al found that the grain size of Mg alloys decreased from 80 µm to 1.5 µm after thirty-two passes at 603 K [63].…”

The Role of LPSO Structures in Corrosion Resistance of Mg-Y-Zn Alloys

“…It is worth mentioning that the method of production and its parameters also influence the corrosion resistance of Mg-LPSO alloys. As reported by Wang et al [24], the number of passes during equal channel angular pressing (ECAP) has a major effect on the corrosion resistance of Mg-1Y-0.5Zn; however, there is no straightforward dependence showing that with the increasing number of ECAP passes, the corrosion resistance increases.…”

Influence of pH on the Formation, Composition and Protectiveness of Fluoride Conversion Film Deposited on AZ31 Magnesium Alloy in KF Solution

“…Additionally, they also demonstrate superior abilities to accelerate the osseointegration rate, enhance bone healing and prevent the biofilm formation [1][2][3][4]. More importantly, they have outstanding biodegradability, and their degradation products can promote the growth of new bone [5][6][7][8][9][10][11][12][13][14]. Thereby, they are deemed as promising orthopedic alternatives to traditional metal implants, such as 316L stainless steels, Ti6Al4V alloys and cobalt-chromium-based alloys [1][2][3][4].…”