Crystallographic characterization and indentation mechanical properties of LaB₆-ZrB₂directionally solidified eutectics

Fabrication, microstructure and properties of in situ synthesized B4C^|^ndash;NbB2 eutectic composites by spark plasma sintering

“…In case of studies on B 4 CNbB 2 eutectics Paderno et al 13) noted that indents made with a load of 150 g did not result in the formation of cracks, which is consistent with the findings of the present investigation (only small cracks were observed at loads of 300 and 500 g). In the present study, increasing the indentation load to 1 and 2 kg resulted in extensive crack growth, 25), 26) enabling the evaluation of K IC . The crack-microstructure interactions for eutectic composite with 35 mol.% NbB 2 are illustrated in Fig.…”

Microstructure and fracture of anomalous eutectic silicon-disilicide composites

“…Unfortunately, there are several significant physical roadblocks to the design of eutectic brittle composites with optimum fracture toughness; in many cases there are limitations imposed by the system thermodynamics or by the processing techniques required to produce them. For example, most in situ ceramic composites are based on binary oxide [7e13], boride [3,4,14,15], and carbide [16e19] eutectic systems. Binary systems provide only narrow composition ranges in which a desirable eutectic structure can be achieved, thereby limiting control over the volume fraction of the minor (i.e., reinforcing) phase.…”

Mechanism of nucleation and growth of directionally crystallized alloys of the B4C–MeB2 system

“…The nature of the outstanding mechanical properties as well as the structure evolution of the directionally crystallized ceramic materials has not been sufficiently studied [1,2]. This limits the choice of chemical composition and processing techniques for fabrication of the high-strength and high-toughness ceramics.…”

“…This is explained by widening of the eutectic region in the multicomponent systems [11]. The change in the interatomic distances of both hexaboride and diboride phases during the crystallization from melt alters the morphology of the eutectic structure [1].…”

“…Simultaneous growth of eutectic grains in the LaB 6 -Me IV B 2 systems within identical supercooling conditions is realized when both phases grow at similar rates [1,2]. The formation mechanism of regular structure in directionally crystallized eutectic LaB 6 alloys is based on the minimum supercooling principle [2,19], i.e., the main contribution into the crystallization comes from the constitutional supercooling of transitional metal atoms at the crystallization front of the LaB 6 matrix [2].…”