MATERIALS TRANSACTIONS
Online ISSN : 1347-5320
Print ISSN : 1345-9678
ISSN-L : 1345-9678
Mechanical Properties of Fine-Grained, Sintered Molybdenum Alloys with Dispersed Particles Developed by Mechanical Alloying
Tomohiro TakidaHiroaki KurishitaMamoru MabuchiTadashi IgarashiYoshiharu DoiTakekazu Nagae
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2004 Volume 45 Issue 1 Pages 143-148

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Abstract

In order to develop Mo alloys with improved mechanical properties of low-temperature toughness and room- and high-temperature strengths without any plastic working after consolidation, fine-grained, particle-dispersed Mo alloys were fabricated by hot isostatic pressing (HIP) or spark plasma sintering (SPS) of mechanically alloyed powders of Mo and 0.8 mol% ZrC or TaC (designated as ZRC08 and TAC08). The fabricated Mo alloys were subjected to high-temperature annealing for 3.6 ks up to 2470 K, three-point impact bending tests at temperatures from 270 to 470 K at 5 m s-1 and static tensile tests at temperatures from 300 to 1970 K at initial strain rates from 4.2 × 10-5 to 8.3 × 10-2 s-1. The fabricated alloys exhibited no significant grain growth even after annealing at 2470 K for 3.6 ks due to the pinning effect of the particles against grain boundary migration. The ductile-to-brittle transition temperatures (DBTT) assessed by impact bending were lower and the tensile strengths up to 1770 K were higher for the fabricated alloys than for recrystallized pure Mo. In particular, HIPed TAC08 was superior in low-temperature toughness having the DBTT lower by 30-40 K than recrystallized Mo-La2O3 (TEM) with an elongated coarse-grained microstructure. HIP- or SPS-treated ZRC08 was superior in room- and high-temperature strengths, respectively. Furthermore, HIPed ZRC08 showed a large elongation of 551% at 1770 K. These excellent mechanical properties of the fabricated Mo alloys were obtained for the first time in the as-consolidated state without subsequent plastic working, and are attributable to fine-grained microstructure and grain-boundary strengthening by the fine particles.

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© 2004 The Japan Institute of Metals and Materials
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