Processing, Microstructure, and Properties of Multiphase Mo Silicide Alloys

Abstract

--Q Wi !.< Multiphase Mo silicide alloys containing T2 (Mo#iBz), Mo$i and Mo phases were prep~d by'b oth melting & casting (M&C) and powder meta.hrgical (PM) processes. GIassy phases we observed in PM materiais but not in M&C materials. Microstructural studies indicate that the primary phase is Me-rich solid solution in alloys containing <(9.4Si+13.8B, at. %) and T2 in alloys with 2(9.8Si+14.6B). An eutectic composition is estimated to be close to Mo-9.6Si-14.2B. The mechanical properties of muhiphase silicide alloys were determined by hardness, tensile and bending tests at room temperature. .The multiphase alloy MSB-1 8 (Mo-9.4Si-13.8B) possesses a flexure strength distinctly higher than that of MoSi2 and other Mo#i~silicide alloys containing no Mo particles. Also, MSB-18 is tougher than MoSi2 by a factor of 4.

Microstructure and mechanical behaviour of reaction hot pressed multiphase Mo–Si–B and Mo–Si–B–Al intermetallic alloys

“…Through WDS analysis, the a-Mo has been found to contain 2 at.% Si in solid solution. The concentration of B in solid solution determined indirectly, from the difference between unity and sum of atom fractions of Mo and Si, to be 1 at.% is at best approximate, and is close to that mentioned by Liu et al [13]. Error also arises due to the possibility of presence of small concentration of O in solid solution, originating in Mo powders used as raw material (Table 1).…”

Influence of Vanadium Additions on the Performance of Mo&lt;sub&gt;3&lt;/sub&gt;Si

“…Alloys surfaces without cracking were obtained in all range of compositions. Using the IPA software, morphological analyses reveals an average grain size of 195, 260 and 380 µm respectively for the above mentioned alloys; evidently these grain sizes are produced due to the annealing treatment and the presence of the second phases that precipitate along the grain boundaries [3] [4] [5] as was mentioned in the area fraction analyses.…”

“…X-ray diffraction patterns of the alloys are shown in Figure 2, where it can be observed for the case of the alloys with low vanadium content the apparition of the Mo 5 Si 3 as secondary phase together with the Mo 3 Si (main phase), while the sample with 53 at.% V presents the apparition of the V 5 Si as secondary phase, being V 3 Si the primary phase. The presence of the observed second phases can be attributed mainly to the silicon evaporation [5] heat treatment processes where the absence of silicon atoms generate the A15 structure transformation and for consequence formation of secondary phases [7] [8].…”

“…Alloys produced from molybdenum and silicon have been studied for many years, especially because the resultant intermetallic compounds present good properties under extreme conditions [1] [2]. In particular, good mechanical properties are absent in A-15 structured materials [3] [4] [5], for such reason some authors [6] [7] [8] have investigated this type of intermetallics compounds, evaluating their mechanical properties at room and high temperature as well the room temperature fracture toughness and hardness looking for a possible improvement [9]. Mechanical properties in V 3 Si single crystals at high temperature have been investigated with interesting results showing the effect of the internal defects in crystal lattice [10].…”

Processing, Microstructure and Creep Behavior of Mo-Si-B-Based Intermetallic Alloys for Very High Temperature Structural Applications

“…The mechanical properties of this class of alloys have also been studied [11][12][13][14][15][16][17][18][19][20][21][22][23]. The Mo3Si and T2 intermetallic phases retain high strengths up to 1400°C [13][14][15][16], but are extremely brittle, with room temperature fracture toughness values on the order of 3 MPa-√m [13].…”