Influence of heat treatment and microstructure on the corrosion of magnesium alloy Mg-10Gd-3Y-0.4Zr

Abstract

The corrosion of Mg alloy Mg-10Gd-3Y-0.4Zr, in the as-cast (F), solution treated (T4) and aged (T6) conditions, was investigated in 5% NaCl solution by immersion tests and potentiodynamic polarization measurements. The as-cast (F) condition had the highest corrosion rate due to micro-galvanic corrosion of the a-Mg matrix by the eutectic. Solution treatment led to the lowest corrosion rate, attributed to the absence of any second phase and a relatively compact protective surface film. Ageing at 250°C increased the corrosion rate with increasing ageing time to 193 h attributed to increasing micro-galvanic corrosion acceleration of the Mg matrix by increasing amounts of the precipitates. Ageing for longer periods caused a decrease in the corrosion rate attributed to some barrier effect by a nearly continuous second-phase network. Electrochemical measurements did not give accurate evaluation of the corrosion rate in agreement with the immersion tests.

Microstructure, mechanical and corrosion properties of Mg–Dy–Gd–Zr alloys for medical applications

“…Moreover, in Mg-Gd-Y alloys Mg 5 (Gd+Y) intermetallics act as cathode and form galvanic corrosion couples with α-Mg matrix, accelerating corrosion [48,49]. Therefore, it can be deduced that the second phase particles in Mg-Dy-Gd-Zr also form galvanic corrosion cells with α-Mg matrix and this is consistent with the corrosion morphology (Fig.…”

Influence of Nd and Y additions on the corrosion behaviour of extruded Mg-Zn-Zr alloys

“…However, their poor corrosion resistance in comparison with other metals has greatly retarded further applications. Many intensive and extensive fundamental investigations and evaluations about the corrosion problem of magnesium alloys have been carried out during the past decade [1][2][3][4][5]. However, most of these investigations devoted their research work to the as-cast alloys, such as AZ91D and AM50.…”

The role of β1′ precipitates in the bio-corrosion performance of Mg–3Zn in simulated body fluid

“…It is well known that microstructure plays an important role in the corrosion performance of materials [5][6][7][8]. For instance, variation of the morphology, volume fraction and distribution of secondary phases can change the corrosion resistance [9,10].…”

“…Liang [12] found that the presence of basecentred orthorhombic b 0 precipitates after ageing results in the decreased corrosion resistance of Mg-7Gd-3Y-0.4Zr. Ageing decreases the corrosion resistance with increasing ageing time to 193 h, due to the formation of precipitates (b 00 (DO 19 ), b 0 (cbco) and b 1 (fcc)) in Mg-10Gd-3Y-0.4Zr alloy [8]. Precipitates of different sizes may have different effects on the corrosion resistance of the alloy system.…”

“…For instance, the small second phase with different types or precipitation sequences accelerates the corrosion as a galvanic cathode. However, the corrosion resistance of Mg-10Gd-3Y-0.4Zr alloy increases after a long time ageing (500 h), because the large precipitates formed in a type of continuous network acted as corrosion barriers [8]. There is however no clear relationship identified between bio-corrosion resistance and microstructure of Mg-Zn alloys.…”