Abstract

Shape memory effect is a peculiar property exhibited by certain alloy system in the β-phase fields, with chemical compositions, which is characterized by the recoverability of two certain shapes of material at different temperatures.  These alloys possess two unique abilities: the capacity to recover large strains and to generate internal forces during their activation. This phenomenon is initiated with thermal and mechanical treatments on cooling and deformation, and performed thermally on heating and cooling, with which shape of material cycles between original and deformed shapes in reversible way. Therefore, this behavior can be called Thermoelasticity.

The basis of this phenomenon is result of the stimulus-induced structural phase transformations, thermal and stress induced martensitic transformations, which govern the remarkable changes in internal crystalline structure and properties of the materials. Thermal induced martensitic transformation occurs on cooling, with cooperative movement of atoms in <110 > -type directions on the {110} - type planes of austenite matrix, along with lattice twinning and ordered parent phase structures turn into twinned martensite structures. The twinned structures turn into detwinned structures by means of stress induced transformation with deformation. Martensitic transformations are diffusionless transformations, and movements of   atoms are confined into the neighbour atom distances. This is plastic deformation, due to the soft character of these alloy in low temperature condition. Strain energy is stored in the material with deformation and released upon heating, by recovering the original shape.

Prof. Ying Yu

Central China Normal University

Assoc. Prof  Dhanesh G. Mohan

Zhengzhou Research Institute, Harbin Institute of Technology, Zhengzhou, Henan, China

Additive Manufacturing of Nickel-Based Superalloys

The capability to produce components out of high-performance metals through additive manufacturing technologies attracts manufacturers to develop more complex parts but require parts to maintain their structural reliability in required operating environments. At ambient and elevated temperatures, nickel-based superalloys have excellent mechanical, creep, wear, and oxidation properties. However, the relationship between process parameters and the resulting microstructure is still poorly understood. Control of the microstructure, particularly the precipitation of secondary phases, is critical to the performance of nickel-based superalloys. The additive manufacturing methods used to process nickel-based superalloys and the influence of the process parameters on mechanical and microstructure properties are portrayed here.

Rational Design of Mutifunctional Nano-structures toward Sustainable Chemical Resource and Beyond 

Mutifunctional nano-structured materials with novel properties, e.g., magnetism, optics, electricity, and catalysis have received enormous attention from the entire world, which largely depend on their precise tailored structures and chemical compositions. In this talk, various carbon and spinel-structured materials with controlled fabrications and green conversions and solar harvesting and beyond are initially reviewed, the composition and structure of spinels will be briefly introduced and illustrated.Secondly, some of the recent advances in the preparation and characterization of mutifunctional nano-structured materials are accordingly summarized, and new strategies are specifically highlighted. The physico-chemical characteristics of mutifunctional nano-structured materials such as their interfacial structures, richful morphologies and derived  defects have been rationally regulated through various approaches, which could 

incur them with improved catalytic conversion to fine chemicals and energetic utilization as well as conversion shall also be discussed in terms of the tailored surface-interface structures of the afore-mentioned nnaocomposite materials.