Guan Shaokang

Age Hardening of AlCrMoNiTi High Entropy Alloy Prepared by Powder Metallurgy

Abstract The AlCrMoNiTi high entropy alloy was prepared by powder metallurgy process. Its microstructure and hardness of as-cast and annealed state were studied. The results show that the as-cast alloy exhibits a mixture of the dendrite (Cr, Mo)-rich bcc phase and the interdendrite (Al, Ni, Ti)-rich fcc phase. The aged alloy can obtain a peak hardness HV of 6150 MPa at 900 °C, and then anneal softening occurs at 1000 °C, but its hardness HV still maintained at a high level of 5160 MPa. This shows that the AlCrMoNiTi alloy exhibits a good high-temperature age hardening performance. Age hardening of the alloy is mainly attributed to the grain refinement strengthening at 800 °C and the precipitation hardening of the second phase (bcc2) at 900 °C. The disappeared second phase and grain coarsening are the main reasons for the softening anneal at 1000 °C.

EBSD Study on the Superplastic Deformation of Mg-7.0Al-0.4Zn Magnesium Alloy

Abstract The superplastic deformation mechanism of Mg-7.0Al-0.4Zn alloy was studied by EBSD technology. Results indicate that with increasing of strain amount, the texture of {0002}//ED is strengthened obviously, and intragranular sliding plays a main role during the accommodated deformation. Twins have started at the medium and the final deformation stages; when approaching to failure, intragranular sliding vanishes, and twins replace it to play a main role. But the contribution of twins to deformation is relatively small.

Superplasticity and Deformation Mechanism of Mg-7.0Al-0.2Zn Alloys

Abstract Superplasticity and deformation mechanism of Mg-7.0Al-0.2Zn (AZ70) alloys without typical fine-grained structure was investigated. It is indicated that the AZ70 alloy exhibits superior superplasticity and the maximum elongation of 191.5% was obtained at 380 °C and 1×10 −3 s −1 . It is worth mentioned that high-strain-rate ( =1×10 −2 s −1 ) superplasticity with elongation of 161.5% was achieved at 380 °C. The mean grain sizes increase with temperature increasing and strain rate decreasing. The grain boundary sliding (GBS) is the dominant deformation mode of the superplasticity, which is verified by grains remaining equiaxial during deformation. Cavities form and grow up along grain boundary. And then the growth and connection of cavities results in the final failure. SEM morphology of the failure surface shows typical tenacity failure characteristics with quantities of uniform dimples.

A binder phase of TiO based cermets

A binder phase of TiO based cermets, a kind of imitated gold materials, was developed by adding active element Si to Fe-Cr alloy, and the related mechanisms were studied. The wettability, matching in thermodynamics and interfacial strength were investigated by the high temperature sessile drop method and element area scanning. The linear expansion coefficients of the materials were measured using TAH100 thermal analyzer. The results show that the wettability of Fe-Cr alloy on TiO are small, with a wetting angle about 90°. After adding some Si in Fe-Cr alloy, its wetting angle can be decreased to about 25°, the interfacial reactions can be prevented effectively and high interface binding can be formed. Fe-25%Cr-1.5%Si matches the thermal expansion coefficient of TiO, so it is a kind of relatively perfect binder for TiO based cermets imitated gold.