Mengqi Cong

Indentation creep behaviors of Mg61Cu28Gd11 and (Mg61Cu28Gd11)99.5Sb0.5 bulk metallic glasses at room temperature

Abstract The room temperature creep behaviors of Mg 61 Cu 28 Gd 11 and (Mg 61 Cu 28 Gd 11 ) 99.5 Sb 0.5 bulk metallic glasses (BMGs) were revealed by means of nanoindentation technique. The creep mechanism was explored by characterization of creep rate sensitivity, creep compliance and retardation spectra. The results showed that the experimental creep curves could be well described by a generalized Kelvin model. The low creep rate sensitivity of both Mg-based BMGs indicated that their room temperature creep was dominated by localized shear flow. In addition, the (Mg 61 Cu 28 Gd 11 ) 99.5 Sb 0.5 glassy alloy exhibited lower creep rate sensitivity, creep compliance and milder retardation peak, indicating its higher creep-resistance and less relaxed state. Furthermore, the creep retardation spectrum consisted of two relatively separated peaks with the well defined characteristic relaxation times.

Effect of Gd on microstructure, mechanical properties and wear behavior of as-cast Mg–5Sn alloy

Effect of minor Gd addition on the microstructure, mechanical properties and wear behavior of as-cast Mg–5Sn-based alloy was investigated by means of OM, XRD, SEM, EDS, a super depth-of-field 3D system, standard high-temperature tensile testing and dry sliding wear testing. Minor Gd addition has strong effect on changing the morphology of the Mg–5Sn binary alloy. Gd addition benefits the grain refinement of the primary α-Mg phase, as well as the formation and homogeneous distribution of the secondary Mg2Sn phase. The mechanical properties of the Mg–5Sn alloys at ambient and elevated temperatures are significantly enhanced by Gd addition. The wear behavior of the Mg–5Sn alloy is also improved with minor Gd addition. The alloy with 0.8% Gd addition exhibits the best ultimate tensile strength and elongation as well as the optimal wear behavior. Additionally, the worn surface of the Mg–5Sn–Gd becomes smoother in higher Gd-containing alloys. The best wear behavior of alloy was exhibited when Gd addition was up to 0.8%, showing a much smoother worn surface than that of control sample. The improvement of tensile properties is mainly attributed to the refinement of microstructure and the increasing amount and uniform distribution of Mg2Sn phase. The larger amount of Mg2Sn phase uniformly distributed at the grain boundary of Mg–Sn–Gd alloys act as a lubrication during sliding, and combined with smaller grain size improve wear behavior of the binary alloy.

Crystallization kinetics and corrosion behaviors of Mg61Cu28Gd11 and (Mg0.61Cu0.28Gd0.11)99.5Sb0.5 amorphous alloys

Abstract 0.5% (molar fraction) Sb was added to Mg 61 Cu 28 Gd 11 glass forming alloy to improve its thermal stability and corrosion resistance. The crystallization kinetics of Mg 61 Cu 28 Gd 11 and (Mg 0.61 Cu 0.28 Gd 0.11 ) 99.5 Sb 0.5 amorphous alloys was investigated under continuous heating. The temperatures of glass transition, onset and peak crystallization for the two glasses exhibit strong heating-rate dependence. The activation energies for the onset and peak crystallization were determined based on the Oawza plots. Vogel-Fulcher-Tamman equation analysis shows that the larger strength parameter and much longer relaxation time are obtained due to the Sb addition. The corrosion properties of the two glassy alloys were studied by means of potentiodynamic and immersion tests. Compared with the parent alloy, (Mg 0.61 Cu 0.28 Gd 0.11 ) 99.5 Sb 0.5 glassy alloy exhibits a superior corrosion resistance in Cl − -containing alkaline solution, as indicated by the lower passive current density and corrosion rate. Based on the point defect model, the effect mechanism of Sb addition on corrosion resistance of Mg-Cu-Gd glassy alloy is carefully identified.