Effects of Gd/Nd ratio on the microstructures and tensile creep behavior of Mg–8Al–Gd–Nd alloys crept at 423K
Jiandong Yang, Wuxiao Wang, Min Zhang, Jian Liu, Shaoyong Qin, Zihe Qin, Lei Chen
Abstract
The specific Nd/Gd mass ratios were designed for optimizing the microstructure of the Mg–8Al–Nd–Gd alloys, and the strengthening mechanism of Al-Gd-Nd phase in the creep process was revealed. The Mg–8Al-1.0Gd-1.0Nd (T6) at Gd/Nd ratio of 1:1 exhibited excellent tensile creep resistance at 423 K/60 MPa, owing to the diffusely distributed Al 2 RE and the fine Al 11 Nd 3 particles, which hindered the motion of dislocations and grain boundary sliding . The stead-state creep rate and creep strain of the alloy were 1.03 × 10 −8 s −1 and 0.312%, respectively, which were superior to that of AZ91 alloy. It could be verified that Gd showed little aging precipitation strengthening effect, while it made the typical rod-like Al 11 Nd 3 evolved into dot-like phase. A TEM thin foil was extracted by focused ion beam (FIB), and the result showed that Nd occupied the Gd sites to form Al 2 (Nd + Gd) solid solution . The TEM bright-field image was taken along the B = [ 1 ¯ 1 ¯ 01 ] Mg zone axis with diffraction condition g = 10 1 ¯ 1 ¯ and Two-beam dark field image with diffraction condition g = 11 2 ¯ 0 , which demonstrated the activation of <a> and <a+c> dislocations during creep deformation.