Odlewany kompozyt aluminiowy in situ umiacniany cząstkami borków tytanu

Przedstawiono syntezę borku tytanu TiB2 metodami: klasycznej syntezy SHS, syntezy SHSB oraz syntezy z soli. Umotywowano stosowanie cząstek borków tytanu jako fazy wzmacniającej w kompozytach. Przedstawiono struktury otrzymanych w ten sposób materiałów kompozytowych. Wykonano badania rentgenostrukturalne w celu identyfikacji faz tworzących się w osnowie aluminiowej po zajściu w niej wysokotemperaturowej reakcji syntezy borków tytanu.

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Mechanical properties of aluminium and its alloys can be improved by transformation of traditional material into a composite. This can be achieved by introducing to aluminium matrix the ceramic reinforcing particles, which gives material characterised by a high value of the strength/density ratio, specially at elevated temperatures. The reinforcing phase are mainly particles of SiC, TiC, Al2O3, and TiB2 - recently in wide application. From among various methods used for composite synthesis [4, 6, 7] the authors have chosen an in situ method. Among numerous materials which can be used as a reinforcement, the TiB2 particles are of particular interest as they are characterised by high hardness, high melting point and low density. From among various methods of the in situ synthesis, for TiB2 the authors have chosen the following variants: the TiB2 synthesis by traditional method of self-propagating high-temperature synthesis SHS, the TiB2 synthesis by self-propagating high-temperature synthesis in bath SHSB, the TiBi synthesis due to the reaction of exchange between the salt components. Due to the chemical reaction: m. K2TiF6 + 2n KBF4 = (m. + 2n) TiB2 + potassium fluorides. A titanium boride was formed which in the form of very fine suspension was transferred to aluminium matrix and settled in the interdendritic spaces. Conclusions: The self-propagating high-temperature synthesis of TiB2 takes place in a Ti-B-AI system resulting in the formation of a composite with the TiBi reinforcing phase. The crystals in this phase are relatively large (about 10 micrometers), while the composite material is porous. Applying the SHSB method and cooling of suspension in a die it is possible to produce a cast AI/TiB2 composite of the pre-assumed volume content of the reinforcing phase with particles rather small in size and amounting to 0.5 micrometers. From the studies it follows that the smallest particles of TiB2 of dimensions, are obtained in an AI/TiB2 composite due to the synthesis of these particles from a salt followed by a high cooling rate of the suspension.