Executive Summary : | The automobile industries are presently using Mg alloys owing to their high specific strength. The potential of Mg alloys in automobile use is the powertrain components subjected to 150-300 ºC. The materials for such application must exhibit good elevated temperature mechanical properties, especially creep resistance. The researchers developed many creep-resistant Mg alloys. Unfortunately, the most cost-effective Mg alloys have poor yield strength and poor creep resistance, and therefore, they cannot be employed at such a high temperature. AZ91 is still a workhorse alloy for automobile industries; however, this alloy has drawbacks of the drastic reduction in tensile properties and creep resistance above 130 °C. Less Al-containing alloys like Mg-Al-Si (AS) and Mg-Al-RE (AE) were developed to overcome this problem, and they exhibited improved high-temperature properties. However, AS alloys offer only borderline improvement in creep resistance, whereas AE alloys have cost disadvantages owing to the costly RE addition. Thus, several attempts were made to improve the creep resistance of the Mg-Al-based alloys by adding RE, Ca, Si, Sn, Sb and so on. In this effort, the Mg-Al-Ca alloys have shown great promise as they exhibit good creep resistance, good castability and are the most cost-effective. Ca is lighter than Mg, and it is less expensive than RE. Therefore, the Mg-Al-Ca alloys have the beneficial effect of retaining the low density of the component. Moreover, Ca reduces the burning tendency and prevents oxidation of Mg melt and reduces corrosion of Mg. Generally, 0.3Mn (wt.%) is added to Mg alloy to improve corrosion performance. It has been reported recently that the minor Mn addition improved the creep resistance of Mg alloys to a great extent. Thus, the other potential alloying element for developing low-cost Mg alloy is Mn. The Mg-Al-Ca alloys are suitable up to 190 °C. The application of the Mg-Al-Ca alloys in particular, and Mg alloys, in general, are restricted up to 200 °C. For powertrain components (above 200 °C), MMCs need to be developed. For reinforcement, long continuous fibres are ruled out because of high cost, and whiskers are not encouraged due to health hazards. The short fibre reinforced MMCs are also expensive and have anisotropic properties. The nanocomposite containing a small volume fraction of nanoparticles provides the optimum solution in terms of properties, anisotropy and cost. The additions of nanoparticles in Mg alloys exhibited improved tensile properties. However, the literature investigating the creep behaviour of the nanocomposites is very limited, and most of the studies were not on the creep-resistant Mg alloy. Therefore, it is not yet explored how far the creep resistance of the already developed creep-resistant Mg alloys can be improved by the addition of nanoparticles. Thus, the present proposal aims at initiating work on the creep and tensile behaviour of the SiC nanoparticles reinforced Mg-Al-Ca-Mn alloys. |