The Pilling-Bedworth Ratio of Oxides Formed From the Precipitated Phases in Magnesium Alloys

Abstract

The Pilling-Bedworth ratio of oxides preferentially formed from the precipitated phases in magnesium alloys were calculated. The results showed that the PBR value of Nd2O3 preferentially formed from Mg12Nd was 1.0584, and the PBR value of Y2O3 preferentially formed from Mg24Y5 was 1.1923. Both the Nd2O3 and Y2O3 would provide a good protection to the Mg matrix. The Gd2O3 preferentially formed from Mg3Gd, whereas the MgO preferentially formed from MgNi2. The PBR value of these two oxides were both larger than 2. The corresponding oxides formed from the common precipitated phases Mg17Al12, MgZn2, MgCu2, Mg2Ca, Mg12Ce, and MgAg were all less than 1. The oxide films formed on surfaces of pure Mg and Mg-xY (x = 3, 5, 7 wt.%) alloys at high temperatures were analyzed. The results showed that the oxide films were composed of a Y2O3/MgO outer layer and an inner layer rich with Y2O3. The formation of Y2O3 was mainly caused by the oxidation of Mg24Y5. The more Y2O3 existed in the composite oxidation film, the better corrosion resistance of the Mg-Y samples.

Thermal Stability of Mg2Si0.6Sn0.4 under Oxidation Conditions

“…52 In recent works, a binary alloy is considered as the source of the metal which will be oxidized for the calculation of the PBR. 53,54 Applied to Mg 2 Si and Mg 2 Sn, which are the "binary border alloys" of Mg 2 Si 1−x Sn x , the PBR values are included in the range 0.73−0.88. This interval frames the value calculated only from the volume of MgO and pure Mg (0.81).…”

Method for Benchmarking Li Metal Anodes: A Mandatory Step toward Reliable Lithium Metal Batteries

“…However, for some metals such as lithium, the oxide layer cannot protect the metal. In corrosion, this feature is well known and can be anticipated by calculating the so-called Pilling-Bedworth ratio (PBR) value of the oxide film [16]. Essentially, a PBR ratio >2 does not protect the surface of the metal because the oxide layer chips off (such is the case for iron, for instance).…”

Enhanced Mechanical Properties, Corrosion Resistance, Cytocompatibility, Osteogenesis, and Antibacterial Performance of Biodegradable Mg–2Zn–0.5Ca–0.5Sr/Zr Alloys for Bone‐Implant Application

“…[8] However, Mg has the lowest standard electrode potential compared to iron and zinc (Zn), indicating that Mg is chemically reactive and forms magnesia (MgO) products on its surface, which are soluble in water and thus ineffective in protecting its substrate. [9,10] Therefore, the complete degradation cycle of Mg alloy implants is generally shorter than the time required for bone healing at the damaged site, which is normally more than 18 weeks, thus showing inadequate mechanical stability. [11] In general, Mg alloy implants can only provide a stable mechanical environment at the initial stage of fracture healing and there is still no effective and sustained stress stimulation in the middle and late stages, resulting in local osteoporosis and refracturing.…”