Effect of gadolinium on aged hardening behavior, microstructure and mechanical properties of Mg-Nd-Zn-Zr alloy

• Published in: Transactions of Nonferrous Metals Society of China 2008-12, Vol.18 (Special 1), p.s27-s32
• Main Authors: LI, Jie-hua, JIE, Wan-qi, YANG, Guang-yu
• Format: Article
• Language: English
• Subjects: mechanical properties; Mg-Nd-Zn-Zr alloy; microstructure; precipitates; TEM
• ISSN: 1003-6326
• DOI: 10.1016/S1003-6326(10)60169-0

Mg-3.4Nd-0.1Zn-0.40Zr alloy samples with and without containing gadolinium (0.6%, mass fraction) were prepared by sand casting. The aged hardening behavior, solidification microstructures and mechanical properties of the alloys were investigated by using the analysis methods of OM, XRD, TEM, hardness tests and mechanical property tests. The main research results are as follows. 1) Compared with the alloy without the addition of gadolinium, the alloys with the addition of gadolinium shows the more remarkable age-hardening response. 2) The as-cast microstructure of the alloy with and without containing gadolinium consists of α-Mg grains with Mg 12Nd phase on the grain boundary. After solution heat-treatment, Mg 12Nd phase of the alloy without containing gadolinium is dissolved in the matrix, however, there is still discontinued Mg 12Nd phase at grain boundary of the alloy with containing gadolinium. The more finely dispersed precipitates in Mg matrix are formed in the alloy with containing gadolinium during age-treatment. 3) The room temperature and high temperature mechanical properties of the alloy are satisfactory, with σ b=280 MPa, σ 0.2=165 MPa at RT and σ b=215 MPa, σ 0.2=155 MPa at 250 °C. The high temperature mechanical properties decrease slightly with the increase of temperature.