Papers by Author: Nikolay A. Belov

Abstract: The structure and phase composition of dispersion-strengthened composite materials based on multicomponent aluminium alloys of the Al–Cu–Mg and Al–Si–Cu–Fe systems at various stages of mechanical alloying were studied by the methods of optical, scanning electron and ion microscopies, electron probe microanalysis and X-ray diffraction analysis. A possibility of the efficient use of commercial scrap of Al alloy chips and initially large strengthening ceramic particles as the base of composite materials was shown, as well as a possibility of synthesis of strengthening particles during the treatment. After mechanical alloying, these materials possessed a homogeneous and disperse structure, high hardness at room and elevated temperatures and a low linear thermal expansion coefficient.

Abstract: The formation of eutectics in Al–Zn–Mg–Ni and Al–Zn–Mg–Si systems is studied by means of metallography, DSC, EPMA, X-ray spectroscopy and thermodynamical calculations. Polythermal sections of the corresponding phase diagrams are constructed. The concentrations and temperatures of binary eutectic reactions L → (Al) + Al3Ni and L → (Al) + Mg2Si in quaternary alloys are determined. Nonequilibrium solidification in Al–7% Zn–3% Mg-based alloys ceases at approximately 480 °C. The alloys close by composition to binary eutectics have considerably improved casting properties as compared to the base Al–7% Zn–3% Mg composition. In particular, hot tearing susceptibility is much less in alloys with Al3Ni or Mg2Si. These results are corroborated by measurements of thermal contraction during solidification. The alloys containing binary eutectics exhibit much lower temperatures of contraction onset and less thermal strain is accumulated in the solidification range. Fine eutectic morphology enables fragmentation and spheroidization of intermetallic particles during annealing. The presence of Al3Ni and Mg2Si particles does not decrease the precipitation hardening effect associated with precipitation of the T′ (AlMgZn) phase. Improved casting properties and good mechanical properties of castings allow the application of Al–Zn–Mg alloys with binary eutectics formed by Al3Ni or Mg2Si as foundry alloys.

Abstract: Al–Cu–Ce alloys have been studied in the Al-rich corner using the microstructural (LM and SEM), thermal (direct and DSC), X-ray diffraction and electron probe microanalysis techniques. Three cross-sections were of particular interest: (a) at 20%Cu (up to 12.5%Ce), (b) at 14%Cu (up to 10%Cu) and (c) at a ratio Cu:Ce=2:1 (up to 10%Ce and 20%Cu). As-cast alloys and those after annealing at 540 and 590°C were studied. Boundaries of appearance of the Al8CeCu4 primary crystals and ternary eutectic involving the phase Al2Cu were determined. The radial cross section (Cu:Ce=2:1) is supposed to be of quasibinary type as ternary eutectic does not form. The temperature and concentrations of the eutectic reaction L–(Al)+CeCu4Al8 were found to be 610°C, 14%Cu and 7%Ce. This binary eutectic has fine microstructure and is capable to fragmentation and spheroidization during heating. The paper considers possibility of using the Al–Cu–Ce system for developing novel Al casting alloys with significantly improved casting properties (hot tearing and fluidity) in comparison with 2xx commercial alloys.