Papers by Author: Zhi Guo Chen

Abstract: The microstructures of Al-0.2Sc and Al-0.2Sc-0.12Zr alloys have been investigated.The results show that Al3Sc and Al3(Sc1-xZrx) dispersoids exist in as-rolled Al-0.2Sc and Al-0.2Sc-0.12Zr alloy respectively, and their orientation is (001)α║(001)dispersoid, [010]α║[010]dispersoid.The Al3Sc particles in as-rolled Al-0.2Sc were precipitated from hot rolling process, while the larger Al3(Sc1-xZrx) particles in as-rolled Al-0.2Sc-0.12Zr from the solidification, and the small particles also from hot rolling process. There is segregation of Sc and Zr in the Al3(Sc1-xZrx) dispersoid, and Sc is rich in the outside shell while Zr rich in the core of the particles. It is believed that the grain and subgrain boundaries can be pinned by the Al3Sc particles when annealed after cold-rolling, and this may lead to restricting the recrystallization of the Sc-containing alloys.And it’s not until the dissolution of Al3Sc that the recrystallization can happen in this kind of alloys.

Abstract: The effects of trace Ce, Ag on the microstructure and mechanical properties of Al-Cu-Li alloy after thermal exposure have been investigated. It’s found that the addition of Ce may lead to a slight increase in mechanical properties after thermal exposure at 107  . The stability of T1 phase is enhanced by independent Ag addition and the combined additions of Ag and Ce,which results in higher strength compared with Ag-free alloy at 150  thermal exposure. However, at 200  exposure, a great number of q¢ precipitates at the expense of T1 may be responsible for higher tensile strength in the Ag-free alloy than that of the independent addition of Ag and combined additions of Ag and Ce alloys.

Abstract: The hot deformation behaviors and microstructure in Al-Cu-Li alloy containing small amount of Ag and Mg were investigated by transmission electron microscopy and isothermal compression tests.When the strain rate is 0.1, 0.01 and 0.001s-1(the deformation temperature within the range of 360-520􀀀 ) and 1 s-1(deformation temperature 520 􀀀 )respectively, the flow stress decreases after a peak value, showing dynamic recrystallization,while the steady-state flow characteristics exist on the other deformation conditions. The flow stress of Al-Cu-Li-Mg-Ag alloy during hot deformation can be expressed by a Zener-Hollomon parameter in the hyperbolic-sine function with the hot deformation activation energyDH of 250.45kJ/mol. The dislocations may climb with support from many vacancies generated during hot deformation, thus forming lots of helical dislocations. The dynamic precipitation and successive dynamic particles coarsening during hot compression have been assumed to be responsible for further flow softening when deformed at low strain rates.