Meta1 matrix composites based on an aluminium alloys were produced by powder metallurgy route, involved unidirectionally hot pressing under 500 MPa for 15 minutes at temperature about 0.95 Ts [Solidus Temperature]. Metal matrix contains different weight percents of SiC, αAl2O3, WC and Si3N4 with different particle size. Wear and mechanical tests have been carried out on composites, and it was found that about 90% of wear reduction occured in composite with 30% SiC compared with pressed matrix

The influence of buoyancy-driven convection on the lamellar spacing of an Al-Zn cutectic was studied under conditions of oriented crystallization. The convection due to huoyancy was affected by the mold position respective to thc direction of action of the force of gravity. It has been found that the buoyancy-driven convection does not oxcrt, any direct effect on the lamellar spacing. Rather, it only affects the rate of advance of tho crystallization front. The lamellar spacing 1 of the Al-Zn eutectic can be described as function of this rate of advance V by the relation 2 = I.'-0.46. 9.0

A study was made of the buoyancy convection of melt provoked by temperature gradient of an orientation identical to that of the gravity vector. The convection was assessed on the basis of temperature fluctuations in the melt. The critical Rayleigh numbers for periodic and turbulent flow were determined. Both periodic and turbulent flow gives rise to transverse "bands" in the structure of the eutection obtained by directional solidification. The intensity of unstable flow affects the number of eutectic crystallites in the sample. B pa6OMe HCCJIeAOBaHHa rpaBHTaUHOHHaR IEOHBeKUUR BbI3aHa rPPAHeHTOM TeMIlepa-TPbI OpHeHTHpOBaHHbIM COrJIaCHO C QaBPiTaUHea. ~OHBeKUHR 6b1na 0UeHHBaHa C no-'IHHLI qHCJIa Rayleigh AnFI B03HHkHOBeHHR IIepHOHHqeCKOrO I4 Typ6yJleHTHOrO ABHMfEeIlHFI paCIlJlaBa. H e c~a 6~n b~o e ABHmeHHe B PaCnJlaBe IlpH HaIIPaBJleHHOg KpHCTaJlJlH3aUHCi CIIOCO6CTByeT B03HHHHOBeHHlU nOIll2pC?sHbIX i'lIOJIOCbI'' €3 CTpykiType 3BTeHTHfFM. r/lHTeHCHB-HOCTb HeCTa6HJlbHOl' O HBHWeHHH PaCIIJlaBa BJIHHeT Ha qHCJI0 3BTeKTH9eCKHX HpHCTaJlJlOB Mouwo @JrloKTyaL@i TeMnepaTypbI B pacnaaee. BLIJIH ycTaHonneHLi KpHTnqecme nem-B o6pa3ue.

A study has been made of the temperature field in an AlZn eutectic melt for a Bridgman-Stockbarger arrangement of the experiment. The influence of the sizes of the ampoules and corundum inserts for the temperature measurements on the final temperature field in the specimen has been studied for different angles a contained by the gravity and the axial temperature field gradient vectors in the specimen. It has been found that an axially located corundum insert increases the convection intensity to a maximum at angles a between 45 and 60". An influence ofthe insert for a = 0" IS almost negligible. Wccnenosanocb TeMnepaTypHoe none B pacnnase ~B T~K T U K BAlZn npa pacnonoxeHuu s~cnepa-Mema E i p u n r~a~-C~o u~6 a p r e p a .Rsy~anocb Bnumne p a s~e p a aMnynbI n pawepa KopyHnoeoro B o6pa3qe npu pa3nar~brx yrnax a ~e x n y s e~r o p o~ rpasu~aqmi a B~KTOPOM a~c a a n b~o r o r p a n a e~r a BHyTpeHHerO YCTpOkCTBa nnX U3MepeHUR TeMnepaTypbI H a pe3yJIbTHpyWUee TeMnepaTypHOe nOJK TeMnepaTypbl B 06pasue. EblnO OnpeneneHO, YTO aKCUaJbH0 paCllOJlOXeHHOe KOpyHnOBOe BHyTpeHHee YCTPOkCTBO IIOBbIWaeT HHTeHCIlBHOCTb KOHBeKUIiH 6onbme ECWO B YrJIaX a = 45 -60". BJIliRHUeM BHYTpeHHerO JfCTpOkCTBa npki GL = 0" MOXHO npeHe6peYb.

The directional solidification of an AlZn eutectic based on the Bridgman method has been carri_ed out on the Earth and in orbit on the Russian orbital station in microgravity conditions on a CSK-1 apparatus developed at the Institute of Physics, Czech Academy of Sciences in Prague.From the conditions of growthfurnace rate 0.1 mm/min, axial temperature gradient in the melt approx. 5 K/cmthe study of the microstructure and the measurements of interlamellar spacing, lamellae thickness ai, hardness HK and the anisotropy of linear thermal expansion it follows, that the microstructure of the specimens prepared in outer space shows an overall lower degree of directionality compared with specimens prepared in analogous terrestrial conditions.