Effect of microstructural parameters and Al alloying on creep behavior, threshold stress and activation volumes of molybdenum disilicides

Mitra, Rahul; Sadananda, K.; Feng, C.R.

doi:10.1016/j.intermet.2004.02.033

Cited by 20 publications

(15 citation statements)

References 29 publications

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“…High temperature compressive yield stress follows a trend mostly similar to that observed in microhardness tests described above. 185,186,242,243 In compression tests of [0 15 1]-oriented single crystals between room temperature and 1500uC, Inui et al 185 have arrived at results similar to the trends in microhardness data up to 800uC for different alloying elements (Fig. 24).…”

Section: Effect Of Alloyingmentioning

confidence: 65%

“…The elevated temperature yield strengths of polycrystalline MoSi 2 depend on microstructural parameters such as grain size, 221,[234][235][236] SiO 2 content, 26,[221][222][223][224]235,236 alloying 128,146,185,186,[237][238][239][240][241][242][243] and presence of reinforcements, [24][25][26]154,236,244,245 as well as testing conditions [221][222][223][234][235][236] of temperature and strain rates. The high temperature hardness also depends on the grain size, SiO 2 content and methods of processing.…”

Section: Yielding and Flow Behaviourmentioning

confidence: 99%

“…Effects of alloying with W, Re, Cr, Nb, Zr, Ta, V and Al on hardness and yield strengths of both single and polycrystalline MoSi 2 have been reported in the literature. 104,130,131,144,[184][185][186][237][238][239][240][241][242][243] With the exception of Al substituting the Si site, all the above elements (5M) substitute Mo site to form a compound of the type (Mo (12x) M x )Si 2 . Interestingly, the microhardness measurements of polycrystalline MoSi 2 and its ternary alloys by Harada et al, 239 have demonstrated the hardness of only C11 b structured MoSi 2 -W or Re alloy to be higher that of unalloyed MoSi 2 .…”

Section: Effect Of Alloyingmentioning

confidence: 99%

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Mechanical behaviour and oxidation resistance of structural silicides

Mitra¹

2006

International Materials Reviews

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256

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The need for high performance materials in aerospace, automotive and industrial components operating at temperatures in the range of 1100-1500uC has led to a surge in the research and development of the refractory metal silicide based intermetallics, multiphase alloys and composites. The silicides of Mo, W, Ti, Nb and Cr are attractive for high melting points, strength retention and ductile behaviour, combined with reasonable to excellent oxidation resistance at elevated temperatures. The major limitation to the widespread use of structural silicides is their inherent brittleness and poor fracture toughness at room temperature, which may be improved further by suitable alloying or tailoring composite microstructures or use of innovative processing routes. The high temperature deformation behaviour of the structural silicides is complex, and depends on the composition and alloy content, crystal structure, character of bonding and orientation, microstructural constitution (nature of phases present and volume fraction), and grain size. Over the past decade, the basic character and role of dislocations involved in the deformation of single or polycrystalline samples at different temperatures and strain rates, including creep conditions, have been investigated in order to understand the operating mechanisms and decide on the strategies to further improve the mechanical properties. Oxidation behaviour in different structural silicides has been studied with emphasis on the constitution of the oxide scale and the kinetics of oxidation under different temperature regimes, which also involve pest disintegration at intermediate temperatures. The present study is a review with a comparative assessment of the known mechanisms of deformation, fracture and oxidation along with strategies to improve the properties to the targeted levels and some of the emerging applications of structural silicides.

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Section: Effect Of Alloyingmentioning

confidence: 65%

Section: Yielding and Flow Behaviourmentioning

confidence: 99%

Section: Effect Of Alloyingmentioning

confidence: 99%

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Mechanical behaviour and oxidation resistance of structural silicides

Mitra¹

2006

International Materials Reviews

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256

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“…Lothe [47] has shown that an interstitial impurity atmosphere creates a Peierls-type barrier for dislocation glide, which is also expected for a concentration of point defects around the dislocation core. Activation volumes calculated from the results of constant-load compression creep tests [48] at 1200 °C, performed by incrementing loads, have been found to be 2b 3 and 27b 3 , which further suggests that dislocations in both RHP and Starck MoSi 2 encounter a Peierls-type barrier. On the basis of dynamic in-situ TEM studies on deformation of ͗201͘-oriented single-crystal MoSi 2 samples at 990 °C, Messerschmidt et al [23] have reported that dislocations with b ϭ 1 ⁄2͗111͘ move either by shifting superkinks or by taking curved shapes.…”

Section: Serrated Plastic Flowmentioning

confidence: 87%

High-temperature deformation behavior of coarse- and fine-grained MoSi2 with different silica contents

Mitra

Prasad

Kumari

et al. 2003

Metall Mater Trans A

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The elevated-temperature deformation behavior of polycrystalline molybdenum disilicide (MoSi 2 ), in the range of 1000 °C to 1350 °C at the strain rates of 10 Ϫ3 , 5 ϫ 10 Ϫ4 , or 10 Ϫ4 s Ϫ1 , has been studied. The yield strength, post-yield flow behavior comprising strain hardening and serrations, as well as some of the deformation microstructures of reaction-hot-pressed (RHP) MoSi 2 samples, processed by hot pressing an elemental Mo ϩ Si powder mixture and having a grain size of 5 mm and oxygen content of 0.06 wt pct, have been compared with those of samples prepared by hot pressing of commercial-grade Starck MoSi 2 powder, with a grain size of 27 mm and oxygen content of 0.89 wt pct. While the fine-grained RHP MoSi 2 samples have shown higher yield strength at relatively lower temperatures and higher strain rates, the coarse-grained Starck MoSi 2 has a higher yield at decreasing strain rates and higher temperatures. The work-hardening or softening characteristics are dependent on grain size, temperature, and strain rate. Enhanced dislocation activity and dynamic recovery, accomplished by arrangement of dislocations in low-angle boundaries, characterize the deformation behavior of fine-grained RHP MoSi 2 at a temperature of 1200 °C and above and are responsible for increased uniform plastic strain with increasing temperature. The silica content appears to be less effective in degrading the high-temperature yield strength if the grain size is coarse, but leads to plastic-flow localization and strain softening in Starck MoSi 2 . Serrated plastic flow has also been observed in a large number of samples, mostly when deformed at specific combinations of strain rates and temperatures.

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“…As a result composite and alloying have been proposed as the efficient methods to overcome the problems [14][15][16][17][18]. It has been demonstrated that alloying of MoSi 2 with Al, which leads to formation of molybdenum aluminosilicide, not only improves the mechanical properties but also affects it's low temperature oxidation resistance significantly [12,14,[19][20][21].…”

Section: Introductionmentioning

confidence: 99%