| Magnesium alloys have attracted attentions for structural applications in aseries of fields including aerospace, automotive and other major industries becauseof their lightweight and high strength. However, poor thermal stability hasrestricted the development and application of magnesium alloys. The developmentof a new type of heat-resistant magnesium alloy is an important direction of thecurrent magnesium research.This work mainly utilises the mechanical milling method to prepare a newheat-resistant magnesium alloy. This experimental method is trying to find thevarious alloy composition and process method to improve the thermal stability ofmagnesium alloy. The contents include: (1) experiments of Mg-Ti mixed powdermilling with different components; (2) experiments of evolution in the Mg-Timilling process; (3) suppression performance and hardness test of Mg-Ti powdersby mechanical milling; (4) experiments of the thermal stability of Mg-Ti powder bymechanical milling.This paper compares the XRD results of different components and milling timeof Mg-Ti powder and analyzes lattice parameters of Mg-Ti powder with millingtime, and the powder grain size and microstrain of various components of Mg-Tiwith milling time were analyzed. Secondly, after obtaining the results of XRD, weconducted the SEM experiments of milled Mg-Ti powder to explore the particlemorphology and size evolution of the different components of Mg-Ti powder. Theenergy spectrum analysis of the experimental samples and the back scatteredelectron image analysis are to study the distribution, size and morphology change ofthe Ti phase in the magnesium matrix with the milling time. The suppressionperformance tests of different milled magnesium alloy powders were carried out.Finally, the annealing experiments were conducted to study the thermal stability ofthe milled Mg-Ti alloy. The annealing time and temperature are the two main factorswe considered in the experiments of thermal stability. In addition, we carried out thehardness test to explore the impact of annealing on hardness.The XRD results of Mg-Ti powders with different composition and millingtime show that the change of the lattice parameters of the magnesium powders ismainly decided by the trend of solid solution of titanium atoms into magnesiummatrix and the defects introduced by the intensive plastic deformation duringmilling process. The grain size of Mg-Ti powder was reduced with the increase ofthe milling time, and at the same time, the microstrain was increasing. We found that the titanium content influences both of the speed of grain refinement and theultimate powder grain size. The analysis of the experiment results of SEM showsthat the powder has experienced five phases in the milling process as follows,initiative powder phase, compressing phase, cold welding phase, powdermolding phase, stabilization phase. The increase of the titanium content results insmaller particle size after 60 hours of milling. By analyzing the backscatteredelectrons of the three components powder at different milling time, we can obtainthat the average particle size of titanium phase reduced with the increase of millingtime, and the refinement of the powder particle becomes faster with the highertitanium content,. Suppression of the powder results show that the density of theexperimental powder becomes lower under the same pressure with the increase ofmilling time. Hardness results shows that the higher hardness we can obtain with thelonger the milling time and the more titanium content. The powder annealed atdifferent times and different temperature, it can be analyzed in the annealingprocess, the thermal stability of magnesium alloy increased with the increase of thetitanium content. |
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