Abstract
A new technique has been developed to make dispersion strengthened steels, i. e., oxide particles are sprayed into steel streams. The mechanical properties of the steel with dispersed aluminum oxide or zirconium oxide has been studied.
The main results obtained are summarized as follows:
(1) For fine dispersed aluminium oxide or zirconium oxide of less than 1200Å in particle size, the hardness of the steel increases with their volume fraction, but little change occurs in the hardness of the steel for the osides of 1700 to 2600Å in particle size.
(2) Both of the 0.2 pct. proof stress and tensile strength increase with a volume fraction for fine dispersed oxides of less than 1200Å in particle size.
(3) The increment of the 0.2 pct. proof stress is proportional to the reciprocal of the planar interparticle spacing in this case, and this fact supports Orowan's by passing mechanism. The work hardening behabior of this steel can be explained by the theory of Fisher-Hert-Pry or Ashby.
(4) An increase in transition temperature (Tr E) and a decrease in maximam absorbed energy are observed as a volume fraction of particles increases. By the observation of the fracture surface, it is obvious that the existence of finer particles has little effect on ductile fracture surface.
(5) From these results, it is found that the steels are strengthened by spray-dispersion of oxides of below 2 volume pct..
