The nanocrystalline alloys: the structures and properties

摘要

We were interested in studying the strength and, plasticity, the structure of nanograins and their boundaries for nanocrystalline polyphases alloys. We have investigated nanocrystalline, Fe_(73.5)Nb_3Cu_1Si_(13.5)B_9, Fe_(73)Ni_(0.5)Nb_3Cu_1Si_(13.5)B_9, Fe_5Co_(70)Si_(15)B_(10), Pd_(77.5)Cu_6Si_(16.5) and Pd_(81)Cu_7Si_(12) ribbons produced by superfast quenching from the melt followed by fast heating to 723-923K, in vacuum. The annealing time was from 10s to 1 h. The alloy Pd_(81)Cu_7Si_(12) was producedby rapid quenching of melt and crystallized during creep tests in the temperature's range between 623 and 823 K and the stresses between 0.7 and 39 MPa. Under creep at 723 K at stress of 2.1 MPa, the resulting alloy had a nanocrystalline structure with a grain size of <10 nm. Under these conditi-ons the alloy exhibited an elevated plasticity. Also reported are the results of dynamic experiments on teh compaction with temperature of nanocrystalline TiN and Al_2O_3 powder in die ranging 573-873K. Phase composition and the microstructure of alloys were studied using the transmission electron microscopy method. The microstructure of the nanocrystalline Fe_(73.5)Nb_3Cu_1Si_(13.5)B_9 alloy was studied in situ at different stages of crystallization of the amorphous ribbons in the column of an electron microscopy. High-resolution transmission electron mocroscoopy (HRTEM) was used to study the structure of nanophase crystals and their interfaces in nanophase alloys. It was shown that the interfaces between chemically similar nanophases may have different structure. The rensile strength of the alloys was determined by stretching ribbon specimens to failure at a rate of 1.6x10~(-3) - 7x10~(-5) s~(-1) at 293-723K.