Production of Functional Nanocrystalline Materials in Hydrogen

On the example of KS25 and KS37 samarium–cobalt-base commercial alloys and LaNi_4.5Al_0.5 alloy, we show the possibility, in principle, of obtaining functional materials in the nanocrystalline state with the help of a planetary mill in hydrogen medium. Milling with a rotational speed of 600 rpm during 24 h leads to the disproportionation of KS25 and KS37 alloys into samarium hydride and iron–cobalt (cobalt) and of LaNi_4.5Al_0.5 into Ni₃Al and amorphous products. After vacuum annealing up to 1181 K, the main phases of samarium–cobalt materials are recombined. The crystallite sizes after annealing are 58–72 and 70 nm for KS25 and KS37, respectively. We established that LaNi_4.5Al_0.5 alloy is not recombined in vacuum, and the nanocrystalline state in it can be reached by milling up to 30 min. The crystallite sizes constitute 45–78 nm.     

Stiffness of Monolithic Reinforced-Concrete Slab Structures

Materials Science - It is shown that the numerical analyses of slab reinforced concrete structures are, as a rule, based on the classical theory of bending of elastic plates. According to the...     

Circular Disk with Radial Internal Crack Under the Action of Model Contact Loads

Materials Science - We solve the plane problem of the theory of elasticity for a circular disk weakened by an arbitrarily located internal radial crack subjected to the action of a model contact...