Microstructure, interface and mechanical property of the DS NiAl/Cr(Mo,Hf) composite

Effect of growth rate on the tensile properties of DS NiAl/Cr(Mo) eutectic alloy produced by liquid metal cooling technique

“…With TEM examination of microstructures of DS10 alloy, as shown in Fig. 2, very fine Cr(Mo) phase could be observed to precipitate in NiAl phase, or vice versa which is similar to previous studies [6]. The preferential precipitation of primary dendritic NiAl phase in the DS10 indicates that the composition of the alloy falls out of the coupled zone under the more rapid solidification conditions.…”

“…1(b,d,f), microstructure of the longitudinal direction is characterized by a lamellar reinforcing morphology that is aligned parallel to the growth direction and embedded within a NiAl matrix. It should be noted that a needle-like Cr(Mo) phase can be observed in the center of most of the cells, which was also found in other research work [6]. The size of cells decreases with the increasing of withdrawal rates, besides the change in the size of cells, the lamellae also decreases with the increase in growth rate.…”

“…Some researches have shown that directional solidified NiAl-Cr(Mo) eutectic alloy exhibits a promising room temperature and high temperature properties [5]. Recently, Guo's group found that Hf-doped NiAl-Cr(Mo) eutectic alloy displays better creep strength due to solid solution and precipitation strengthening than Hf-free alloy [6], and rare earth elements can improve both the mechanical properties and oxidation resistance [7]. In the present work, a NiAl-Cr(Mo) eutectic alloy doped with both Hf and rare earth element holmium (Ho) is fabricated by directional solidification in order to improve the mechanical properties further.…”

Effect of withdrawal rate on the microstructure of directionally solidified NiAl–Cr(Mo) hypereutectic alloy

“…But the NiAl phase has almost no solubility for Mo [30,31], and it rejected huge amounts of Mo during the solidification process. Due to the small eutectic interlamellar spacing, Mo was laterally diffused to the front of Cr plates.…”

Effects of Hf additions on high-temperature mechanical properties of a directionally solidified NiAl/Cr(Mo) eutectic alloy

“…The withdrawal rate of the alloys was set to 300 mm/h. This fast rate is chosen for (1) that the directional solidification rates from 25.4 to 254 mm/h have no effect on mechanical properties of NiAl-31Cr-3Mo [15], and reducing the Si-contamination [16].…”