TY - JOUR
AU - Hanada, Shuji
AB - To improve the high-temperature strength of Nb-Mo-Ti-Si in-situ composites, alloying with W and a directional solidification technique were employed. The alloy composition of Nb-xMo-10Ti-18Si (x=10 or 20) was used as the base, and Nb was further replaced by 0, 5, 10 and 15 mol pct W. For samples without W, the as-cast microstructure was a eutectic mixture of fine Nb solid solution (Nb
SS
) and (Nb, Me)5 Si3 silicide (Me = Mo, W, or Ti), while large primary Nb
SS
 particles appeared besides the eutectic mixture as a result of replacing Nb by W. The directionally solidified samples consisted of coarse Nb
SS
 and (Nb,Me)5 Si3 silicides, and the microstructure showed a slight orientation in the direction of growth. The maximum compressive ductility (ɛ
max) at room temperature decreased with increasing W content and was in the range of 0.8 to 2.3 pct, in contrast to the Vickers hardness (HV), which increased with W content. The 0.2 pct yield compressive strength (σ
0.2) and the specific 0.2 pct yield compressive strength (σ
0.2S
) (σ
0.2 divided by the density of sample) at elevated temperatures were markedly improved by the W addition. The directionally solidified samples always showed higher σ
0.2 and σ
0.2S
 values than the as-cast samples. At elevated temperatures, the directionally solidified sample with 10 mol pct Mo and 15 mol pct W had the highest σ
0.2 and σ
0.2S
 values; even at 1770 K, σ
0.2 was as high as 650 MPa. The directionally solidified materials alloyed with W exhibited excellent compressive creep performance. The sample with 10 mol pct Mo and 15 mol pct W had a minimum creep rate 

$$(\dot \varepsilon _m )$$

 of 1.4×10−7s−1 and retained steady creep deformation at 1670 K and an initial stress of 200 MPa. Under compression, the damage and failure of these in-situ composites were dominated by decohesion of interfaces between the Nb
SS
 and silicide matrix.
TI - Mechanical properties of As-cast and directionally solidified Nb-Mo-W-Ti-Si in-situ composites at high temperatures
JF - Metallurgical and Materials Transactions A
DO - 10.1007/s11661-003-0210-1
DA - 2003-03-30
UR - https://www.deepdyve.com/lp/springer-journals/mechanical-properties-of-as-cast-and-directionally-solidified-nb-mo-w-QyCBffkOFT
SP - 85
EP - 94
VL - 34
IS - 1
DP - DeepDyve
ER -