Research of liquid structure

The aspect has two research directions:

ⅰ) Research on liquid structure of materials.

Most of materials processing begins with liquid, which is often regarded as the master state of materials. However, the understanding of liquid structure is much far behind that of solid and gas. Internationally at present, the research on liquid structure of materials mainly includes three aspects: direct measurement using X-ray or neutron diffraction, research on liquid physical properties of materials and research by computer simulation method.

At present in this research direction, the laboratory is equipped with the home-unique X-ray diffractometer for direct measurement of liquid structure (made in Ukraine); high-accuracy rotating oscillation viscometer for high temperature liquid (made in Japan) and surface tensiometer for the research on liquid physical properties; and imported from USA the large-scale softwares such as GAUSSION98 for liquid simulation calculation. These enhance the research work and breakthrough evolution has been obtained. In the structure and properties of liquid metals, the non-linear relationship has been revealed between melt structure and temperature of some high temperature metals, which provide the theoretical basis for melt treatment of metals; the relationship has been found between melt structure and glass formability, amorphous and quasicrystalline structure, which opens a novel way for the preparation of metallic glass and bulk amorphous alloys; the conception of thermal-rate treatment was first put forward at home, which founded the theoretical basis for design of thermal history of the melt.

ⅱ) Research on heredity property of materials

Taking advantages of the study results of liquid structure of materials and nano-sized powder, using the non-linear theory, chaos theory, information theory and rapidly developing computer technology, disclose and analysis the hereditary law of materials structure during the complex systematic process of solid-liquid-solid, nano-sized powder sintering and sintering transition, treat and use all kinds of structure information, thus enhance the advantageous structure and shape heredity and cut off the disadvantageous shape mutation; studying the reproductivity and the rational recycling of materials from the viewpoint of mutation, realize the non-pollution and sustainable development strategy during making use of materials; effectively performing the optimum design of heredity carrier, achieve breakthrough in the preparation technique of novel materials possessing special properties such as high-powered, multifunctional and intellectualized.

By way of experiment and computer simulation, reveal the essence of heredity of materials on the atomic level, namely, describe the movement law and characteristics of variation of heredity carrier, and display the whole process of material heredity. Establish the perfect hereditary theory of solid-liquid-solid and the sintering and sintering reaction system of nano-sized powder.

Base on the principle of heredity, a series of high effective master alloys such as Al-Ti-B, Al-Ti-C and Al-P have been produced:

Al-Ti-B and Al-Ti-C master alloys can be used to refine the α-Al grains since TiB2 or TiC ( about 1μm in diameter) can act as the nuclei of Al grains. When Al-Ti-B (or Al-Ti-C) master alloy is added into Al melt in amount of 0.1%, the grain size of the Al alloy will be less than 200mm. Use of the master alloy, especially Al-Ti-C master alloy can provide opportunities in other alloys for cost savings by improved cast or ingot quality and increased production.

Al-P master alloy can be used to refine the primary Si in eutectic and hyper-eutectic Al-Si alloys, since there are lots of AlP compounds in the master alloy and the AlP particles can nucleate primary Si. The larger primary Si will be refined if added less than 0.3% Al-P master alloy into this kind of Al-Si alloy.

As for the mechanical properties, intermetallic is intervenient between metals and ceramics, eliminating the disadvantage of the individual metals or ceramics. Comparing with other Ti-Al or Ni-Al intermetallics, Fe-Al intermetallics attract more attention due to low cost.There exist several intermetallic in Fe-Al system, e.g. Fe3Al, FeAl3, Fe2Al5, and Fe3Al have the excellent oxidation and sulfuration resistance. The liquid structure and heredity information are abundant. Based on the study of structure heredity, the relation of intermetallic structure, properties and raw material, processing is established. Fe-Al/Al2O3 composites, with bend strenth 694Mpa and KIC 8.35MPam1/2, was fabricated by mechanical alloying combining with heat treatment. The study on the field has been award with Provincial First Prize for Science and Technology Progress in 1999.It has conditions to attract internal or external scholars’ co-research.

The laboratory has bought above 100 thousand-yuan equipments worth totally up to 21.765 million yuan since 1995. In recent five years (1995-1999), 240 academic papers has been published, 23 and 53 of them indexed by SCI (Science Citation Index) and EI (Engineering Index), respectively. 4 monographs has been published, and 3 patents obtained. 32 achievements has received awards, including 5 national prizes, 27 provincial and ministerial prizes (2 first order prizes). The laboratory has taken or is taking on 74 research projects, obtains research funds of 14.49 million yuan, including 10 National Natural Science Foundations, 1 national project for tackling key problems, and 1 “863” project