The transverse rupture strength (TRS) or the three-point bending strength and the hardness of Mo2NiB2 alloys, as well as the density data, both reported values and measured ones in this work, were summarized in Table 1. It can be found that the maximum mechanical properties obtained in this work were comparable with the corresponding reported values. However, no strengthening additives were added in the current investigation.
Table 1
Mechanical properties of the obtained alloys compared with the reported values in literature.
The theoretical density was 8.92 g/cm3 calculated in accordance with the rule-of-mixtures and on the hypothesis that the raw powders reacted completely to form Mo2NiB2. The samples sintered at lower temperatures than1200℃ could not reach high relative densities. Consequently, the mechanical properties were not good, and they could be easily ground to powders. The density of the sample sintered at 1100 ℃was 5.09 g/cm3, which was only about 57.1% of the theoretical density.
The bending strength and HRA of the samples first increased and then decreased with the sintering temperature increase, and both of them achieved maximum values at 1250℃ for 40 min holding time. For the sample sintered at 1200℃, the bending strength was just 0.96 ± 0.18 GPa and the hardness was not good enough to be evaluated by HRA. Being sintered at 1250℃or 1300℃, the samples nearly reached the theoretical density and demonstrated high mechanical properties. The bending strength reached 1.85 ± 0.04 GPa and 1.55 ± 0.15 GPa, respectively. HRA reached 85.7 ± 0.1 and 83.6 ± 0.1, respectively. These values were comparable to those reported in literature. On the other hand, however, the optimum temperature for obtaining the maximum TRS and HRA was also lower in the present work. For the samples sintered at 1250℃, the effects of holding time on the mechanical properties were also studied. It was shown that 40 min was a good condition for the mechanical properties, and less or more time was not an advantage.
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