Papers by Author: Xing Zhang

Abstract: In the paper, the high-temperature compression test of BTi-62421S alloy was carried out in the temperature range from 850°C to 1050°C, strain rate range from 0.01 s ^-1 to 30 s ^-1, and the deformation of 70%. The results show that the flow stress of BTi-62421S alloy significantly increased with the decreasing of the temperature and the increasing of the strain rate. By calculating the activation energy of deformation and analyzing the stress-strain curve, it can be seen that the softening mechanism of hot deformation of BTi-62421S alloy is different near the （α+β）/β phase transforming temperature. The softening mechanism of hot deformation is mainly dynamic recrystallization in （α+β） area and it is mainly dynamic recovery above β phase transforming temperature. According to hyperbolic sine model, the alloy’s constitutive equation is established. Key word: BTi-62421S alloy; high temperature figuration; constitutive equation

Abstract: Aluminum (Al) coating was thermally sprayed on the surface of AZ80 magnesium (Mg) alloy. The Al-coating was deformed at 400°C with different deformation degrees of 15%, 30%, 45%, 60% and 80%. The corrosion properties of the AZ80 Mg alloys coated with Al-coatings were studied by potentiodynamic and galvanic tests in 3.5% NaCl solution; the adhesion strengths between Al-coatings and AZ80 substrate were also measured simultaneously by tensile test. The results showed that, Al-coating could decrease the corrosion rate of AZ80 Mg alloys, and the corrosion rate was related not only with the density of Al-coating but also with the adhesion strength of Al-coating. Before the formation of dense Al-coating, the corrosion rate of Al-coated AZ80 Mg alloys decreased with the increasing of bonding strength of Al-coating; after the formation of dense Al-coating, the corrosion rate of Al-coated AZ80 Mg was mainly determined by the structure of Al-coating. It was also revealed that with the increasing of deformation degree, the corrosion rate of the Al-coated AZ80 Mg alloys first decreased then increased, while the adhesion strength increased gradually. The corrosion rate of AZ80 Mg alloy coated with 60% deformed Al-coating was the lowest, which was only 19% of that of the AZ80 substrate.

Abstract: Thermal compression tests of AZ61 magnesium alloy was performed at deformation temperature 150-400°C and strain rates ranged from 0.01s-1 to 10s-1, and the microstructure were observed for deformation specimens. The result shows that dynamic recrystallization (DRX) was happened under the center warm deformation condition for AZ61 alloy. The values of stress peak decrease when the deformation temperature increase, the grain size grows up at the same time. On the other hand, the critical strain increase and the grain size get smaller with the strain ratio increasing. Therefore temperature and strain ratio can make a great effect on the microstructure and mechanical properties of AZ61 alloy, but temperature is a more important factor.

Abstract: Split Hopkinson Pressure Bars (SHPB) was applied to investigate shock resistance of magnesium alloy. The deformation behaviour was reported of ZK60 magnesium alloy at high strain rate, and the relationship was established between the dynamic properties and the impact velocity. Results indicate: with impact velocity improvement, much twinned crystal and fine grain can be obtianed, this made dynamic properties enhancement of ZK60 alloy.