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Aluminum–lithium alloys have been extensively used in the aviation and aerospace field. Now it is one of the critical materials for the production of large aircraft in China. Thermoplastic deformation is one of the key methods to solve the difficulty in the precise deformation of Al–Li alloy parts. The thermoplastic deforming behavior of the Al–Li alloys is characterized by a phenomenological model. The effects of deforming temperature, strain rate, and combining with strain are applied to fit and predict the flow stress in the model. However, the model does not explicitly explain the deformation mechanism. The physical constitutive model takes into account the physical parameters and the microstructure evolution of the material during deformation,such as dislocation density, grain size, and dynamic recrystallization, which is the development trend of the thermoplastic deforming constitutive relationship of Al–Li alloy. In this paper, the researches on the phenomenological constitutive models and physical constitutive models summarized commonly are adopted to characterize the thermoplastic deformation of Al–Li alloys. Besides, the characterization tendency is forecasted. [ABSTRACT FROM AUTHOR]

As more than 50% construction and demolition (C&D) wastes are composed of concrete debris in Hong Kong, recycling this debris into Recycled Aggregate (RA) for production of Recycled Aggregate Concrete (RAC) is an efficient way to alleviate the burden on landfill areas. Since RA is generated from concrete debris which has undergone years of services, the resulting RAC bears the weaknesses of lower density, higher water absorption, and higher porosity that limit them to lower-grade applications. Pinpointing to these weaknesses, Tam et al . [2005, Cement Concrete Res 35(6):1195–1203] developed the Two-Stage Mixing Approach (TSMA) for improving the strength of RAC, leading to the possibility in applying RAC for higher-grade applications. While the improvement in strength by TSMA has been proven in Tam et al.’s work [2005, Cement Concrete Res 35(6):1195–1203], the durability, in terms of deformation (shrinkage and creep) and permeability (water, air and chloride permeability), remains to be verified. In this paper, 0%, 20% and 100% of RA substitutions have been experimented to compare the durability performance of the Normal Mixing Approach (NMA) and the TSMA. Experiment results highlight that: (i) the higher the substitutions of RA, the weaker the performance of RAC; and (ii) the deformation and permeability of RAC can be enhanced when adopting TSMA. Therefore, it demonstrates that TSMA can help to improve the durability of RAC, on top of the previously verified strength improvement, and thus opening up wider applications of RAC. [ABSTRACT FROM AUTHOR]