In order to further improve the performance of the aluminum alloy, nano phase and nano intermetallic compound
dispersion strengthening alloy research has aroused the concern of the national technicians. A new type of alloy
nanoparticles toughening reinforcement, will greatly improve the strength of the material, and reduce the usage amount of
material. Nanoparticles toughening reinforcing material for its high strength, high toughness, low temperature
superplasticity, easy processing, low density, good performance, in the aircraft, spacecraft and automobile industry has a
good application prospect.
Due to the small size effect of nanometer materials and surface and interface effect caused by the increase of surface
atomic activity, so the material sintering is easier. It has the advantages of low sintering temperature, short sintering time,
sintered body with good sintering performance can be obtained. In general, small uniform microstructure and complete
densification is requirements of nanomaterials to achieve the best performance. Traditional molding, isostatic compaction,
extrusion, injection molding, explosive forming of powder metallurgy forming method can be used in nano powder
molding. Pressureless sintering process is simple and is low cost. Hot pressing (HP), isostatic pressing sintering (RS) and
reaction hot-pressing sintering compared with pressureless sintering, the sintering temperature is much lower and higher
density can be obtained.
Microwave sintering (MS), self-propagating high temperature synthesis (SHS), plasma sintering and electric spark
sintering is the latest sintering methods developed in recent years. But because nano powder is extremely fine, its apparent
density is very low, so will cause the compact density is uneven, so that the density of sintered body hard meet the
theoretical density. Although nano powder has great specific surface area, and high sintering activity. Nanoparticles still
grew rapidly at high temperature, and before that have not reached full densification, grain size will grow up to 100 nm.
And thus has method to make block nano materials with fully densification and grain size is less than 100 nm. Therefore,
the research emphasis of the preparation of nanometer materials is the control of grain growing up.
The study found that the heat forging technology can effectively overcome the lack of hot pressing. Such as 1100 ℃ can
make ZrO2-3% Y2O3 fully densification, the average grain size is 85 nm. In addition, the consecutive extrusion forming
and molding in instantaneous high pressure pulse can improve the compact density. Rapid sintering methods such as
microwave sintering, its temperature rising (500 ℃ / min) fast, short heating time (2 min), solved the problem of the
nanometer grain abnormal grew up. Sintered density, however, it is difficult to achieve theoretical density, so
nanomaterials is unlikely to achieve the best mechanical properties.
At present, because of price and technology, the application of powder metallurgy of high strength aluminum alloy is
mainly limited in the field of aviation, aerospace. Along with the advance of technology and development, raw material
costs will continue to decline, will be applied in the automotive industry massively.
