Effects of heat treatment conditions on phase transformation, microstructure and thermal expansion coefficient (TEC) in MgO-Al 2 O 3 -SiO 2 system glass-ceramics were investigated by means of differential thermal analysis, X-ray diffraction and scanning electron microscopy. The magnesium aluminium titanate (MAT) precipitated firstly at 850uC and b-quartz solutions (b-QSS) formed at 950uC. Further increasing temperature to 1000uC, MAT disappeared and b-QSS became master phase, following little amount of a-cordierite, MgTi 2 O 5 , rutile and sapphirine. When glass was treated at 1050uC, b-QSS content decreased and a-cordierite became master phase. As temperature reached higher than 1100uC, b-QSS and sapphirine disappeared, and acordierite became master phase accompany with rutile and MgTi 2 O 5 as secondary phase. The microstructure transformed gradually from particle shape crystallites to slat shape network with the increase in heat treatment temperature. By controlling heat treatment condition, an ideal glass-ceramics with proper TEC for matching sealing to 4J29 alloy has been obtained.
Amorphous Zr 50 Al 15 Ni 10 Cu 25 alloy powders were fabricated by mechanical alloying technique with commercially pure element powders. The effects of small amount of C, Si 3 N 4 and SiC powders addition on the thermal stability and crystallisation behaviour of the Zr 50 Al 15 Ni 10 Cu 25 amorphous alloy were investigated. The blended powders were compacted into bars by oil hydraulic press, and were sintered in argon atmosphere at different temperatures and pressures. The samples before and after sintering were characterised by X-ray diffraction, scanning electron microscopy, differential scanning calorimetry and electron tensile testing machine. The results demonstrated that a proper addition of Si 3 N 4 powders to the amorphous matrix can improve the thermal stability of the matrix. Suitable additives can help to improve the density and mechanical properties of the matrix in sintering process.
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