Formation of nickel aluminides by mechanical alloying and thermodynamics of interaction

Formation of NiAl intermetallic by gradual and explosive exothermic reaction mechanism during ball milling

“…Intermetallic compounds based NiAl are being recognized as potential high temperature structural materials because of their low density (5.86 g/cm 3 ), high melting point (1911 K) and excellent oxidation resistance up to 1573 K, as well as good thermal conductivity [1,2]. These properties have made NiAl a suitable material for structural application such as gas turbine engine rotor blades and stator vanes.…”

Effects of processing and powder size on microstructure and reactivity in arrested reactive milled Al+Ni

“…The variation in the measured composition of powders is less than 1%, which should not prohibit the intermetallic reaction since it may take place above or below its stoichiometric ratio [9]. The measured mass of the grinding media and powders are given along with the temperature change, measured as the relative height of the temperature spike from the thermocouples shown by the peak with a height of 24 ˚C around 9500s in Fig.…”

“…The powder is processed through repeated impacts of a "grinding" media usually made from elastically deforming spherical balls enclosed in a sealed container that produces materials with highly refined microstructures, enhanced strength or meta-stable phases [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16]. This technique has been shown to synthesize intermetallic compounds resulting from gradual and explosive formation at the grain level [3,4,6,[9][10][11][12][13]. A self-sustained hightemperature synthesis (SHS) of intermetallics may release large amounts of heat during intermetallic phase formation on the order of that released by explosives [17].…”

“…A self-sustained hightemperature synthesis (SHS) of intermetallics may release large amounts of heat during intermetallic phase formation on the order of that released by explosives [17]. The gasless reaction from reactive milled (RM) experiments forming nickel-aluminides [3,4,6,[8][9][10]12,15,16,18], titanium-based alloys [5] and combustion reactions in metal-metal-oxides [11,13,14] in a ball-mill are several examples of materials that exhibit SHS.…”

Amorphisation and intermetallic nanophase formation in ball-milled Al–Ti–Si studied through positron lifetime spectroscopy

“…It is first noted that the contribution of the change in entropy to the Gibbs free energies of formation in these cases is negligible and the change in enthalpy in the temperature range from 300 to 400 K provide the necessary driving force for the phase changes. The final product of mechanical alloying is always the phase or phase mixture which has the minimum Gibbs free energy among those of the competing phases at a given alloy composition [23]. The heat of formation of different products-crystalline or amorphous solid solution, intermetallic phase or compound-of a binary system can be calculated using the model proposed by Miedema et al [24,25].…”