NiAl matrix composites modified by ceramic particles addition
Dariusz Kaliński*, Marcin Chmielewski&+*, Mirosław Kozłowski** *Instytut Technologii Materiałów Elektronicznych, ul. Wólczyńska 133, 01-919 Warszawa **Przemysłowy Instytut Elektroniki, ul. Długa 44/50, 00-241 Warszawa Instytut Fizyki PAN, al. Lotników 32/46, 02-668 Warszawa
Quarterly No. 3, 2005 pages 97-102
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abstract NiAl matrix composites with Al2O3, TiC and Cr3C2 particles (Tab. 1) were studied. Composite powders produced by the mechanical alloying technique (Fig. 1) were hot pressed at 1623 K/40 MPa/120 min in argon atmosphere (Fig. 2). As a result almost fully dense materials (98% TD) were obtained (Tab. 2). The porosity of obtained composites was 0.5, 1.0 and 1.8% for NiAl/Al2O3, NiAl/Cr3C2 and NiAl/ TiC, respectively. Addition of TiC leads to 12% increase of the bending strength (664 MPa) in comparison to pure NiAl matrix (595 MPa - tab. 3). However, 24÷28% decrease of bending strength for composites with Al2O3 (429 MPa) and Cr3C2 (452 MPa) particles was found (Tab. 3). The increase of the bending strength is related with the grain size in the sintered materials - NiAl/TiC composites were characterised by small grain size and the homogeneous structure, and due to this reason they have the highest bending strength. Addition of ceramic particles resulted in increasing of the hardness of the composites in comparison with the pure NiAl phase. Significant increase of hardness for all composites with ceramic particles was observed (e.g. in the case of TiC particles almost 85% - Table 3). Results of the density, porosity and bending strength investigations well correspond to microstructure analyses. The microstructure investigations included: optical microscopy, scanning electron microscopy, phase analyses and surface distribution of elements. Microstructure analyses (Figs 3 and 4) showed that mechanical properties of composites studied depend on both: microstructure of composites and properties of ceramic particles used. X-ray analysis did not show any new phases, formed during the sintering process (Fig. 5). High homogeneity of composites was confirmed by WDS technique (Figs 6 and 7). Key words: NiAl intermetallic matrix composite, sintering under pressure, bending strength, hardness