The effect of Ca and rare earths on compressive creep behavior of Mg-4Al alloy was investigated with a special apparatus. The microstructures were analyzed by OM, XRD, SEM and EDS before and after compressive creep test. The results reveal that a small amount of Ca was added into AE41 alloy in order to refine the crystalline structure and improve the creep resistance. Comparing with NdPr rare earths alloy, the creep resistance of LPC rare earths alloy decreases, but is still better than AE41 alloy. The as-cast microstructure of AE41 alloy is mainly composed of α-Mg matrix and Al11Nd3 phase. The acicular Al11Nd3 phase is prone to decompose at high temperature, which leads to the poor creep resistance of AE41 alloy. The acicular Al11RE3 phase is gradually replaced by Al2Ca and Al2RE with Ca addition into AE41. LPC rare-earth mixture is in cluster at grain boundaries so that the creep resistance is worse than that of alloy containing NdPr rare-earth mixture.

Reducing the weight of a vehicle, which helps to reduce fuel consumption and emissions by a large extent, has become a research focus in the automotive industry. Application of magnesium alloy lightweight materials is one of the most lightweight methods. This paper introduces the characteristics of magnesium alloys and reviews the application of magnesium alloys in automotive industry at present.

The compressive creep behavior of Mg-4Al-1RE-1Ca-0.2Sr (AECJ411002) alloy was investigated at temperatures in the range of 125~175°C and different compressive stress in the range of 88~112MPa with special apparatus. The results show that the creep deformation increases with the increasing of temperature and compressive stress. There is linear logarithmic relationship between the steady creep rate and all the temperature and stress used. The steady creep rate obeys an empirical equation. The stress exponents are similar at different temperatures and the appearance activation energies are not greatly different under different stresses. Their average value is respectively 6.19 and 39.05kJ/mol. Material constant A is 4.18×10-14. The steady creep rate is controlled by a dislocation climb led by grain boundary sliding. The creep resistance enhances because of the heat-resistant phases Al2Ca and Al4Sr distributing at grain boundary.