Karlík Miroslav, Průša Filip, Kratochvíl Petr, Thürlová Hana, Strakošová Angelina, Čech Jaroslav, Čapek Jiří, Vronka Marek, Cabibbo Marcello, Ekrt Ondřej
Faculty of Nuclear Sciences and Physical Engineering, Czech Technical University in Prague, Trojanova 13, 120 00 Prague, Czech Republic.
Department of Metals and Corrosion Engineering, University of Chemistry and Technology, Technická 5, 166 28 Prague, Czech Republic.
Materials (Basel). 2023 Mar 21;16(6):2491. doi: 10.3390/ma16062491.
Three mechanically alloyed (MA) and spark plasma sintered (SPS) CoCrFeNiNbX (X = 5, 20, and 35 at.%) alloys with an addition of 5 at.% of SiC were investigated. The face-centered cubic (FCC) high-entropy solid solution, NbC carbides, and hexagonal Laves phase already developed during MA. In addition, the SPS compacting led to the formation of oxide particles in all alloys, and the CrC carbides in the Nb5 alloy. The fraction of the FCC solid solution decreased with increasing Nb concentration at the expense of the NbC carbide and the Laves phase. Long-term annealing at 800 °C led to the disappearance of the CrC carbide in the Nb5 alloy, and new oxides-NiNbO, CrO, and CrNbO-were formed. At laboratory temperature, the Nb5 alloy, containing only the FCC matrix and carbide particles, was relatively strong and very ductile. At a higher Nb content (Nb20 and Nb35), the alloys became brittle. After annealing for 100 h at 800 °C, the Nb5 alloy conserved its plasticity and the Nb20 and Nb35 alloys maintained or even increased their brittleness. When tested at 800 °C, the Nb5 and Nb20 alloys deformed almost identically (CYS ~450 MPa, UTS ~500 MPa, plasticity ~18%), whereas the Nb35 alloy was much stronger (CYS of 1695 MPa, UCS of 1817 MPa) and preserved comparable plasticity.
研究了三种机械合金化（MA）和放电等离子烧结（SPS）的CoCrFeNiNbX（X = 5、20和35原子百分比）合金，其中添加了5原子百分比的SiC。面心立方（FCC）高熵固溶体、NbC碳化物和六方Laves相在机械合金化过程中就已形成。此外，放电等离子烧结致密化导致所有合金中形成氧化物颗粒，以及Nb5合金中形成CrC碳化物。FCC固溶体的比例随着Nb浓度的增加而降低，代价是NbC碳化物和Laves相。在800℃下长期退火导致Nb5合金中的CrC碳化物消失，并形成了新的氧化物——NiNbO、CrO和CrNbO。在实验室温度下，仅含有FCC基体和碳化物颗粒的Nb5合金相对强度较高且韧性很好。在较高的Nb含量（Nb20和Nb35）下，合金变得脆性。在800℃退火100小时后，Nb5合金保持其塑性，而Nb20和Nb35合金保持甚至增加了它们的脆性。在800℃进行测试时，Nb5和Nb20合金的变形几乎相同（屈服强度450MPa，抗拉强度500MPa，塑性~18%），而Nb35合金强度更高（屈服强度为1695MPa，抗压强度为1817MPa）且保持了相当的塑性。
