not come in contact with the heater 3 and the sample 4 was maintained at 973 u00b0 c by thermal radiation heating by the heater 3 the conditions for an oxygen containing gas to be fed to the bell jar type tractor 1 and the plasma generating conditions in the reactor 1 were selected as shown in table 1 under these conditions the sample was subjected to selective oxidation treatment by oxygen containing plasma for 1 hour whereby an internal oxidized alloy was produced on these internal oxidized alloys the degree of internal oxidation was measured using an electron spectrocopy for chemical analysis 34 esca 750 34 manufactured by shimadzu corp and the tensile yield strength was measured using an autograph 34 dss 500 34 manufactured by shimadzu corp this autograph was one remodelled so as to enable high temperature heating by an infrared image furnace with respect to the results of the measurement by the electron spectroscopy for chemical analysis the percentage of internal oxidation of al was determined by 1 separating the peak of al 2s by wave analysis into a peak 1139 ev for non oxidized al and a peak 1136 ev for oxidized and chemically shifted al and 2 calculating the ratio of the respective peak areas the percentage of internal oxidation of cu was also determined using a peak 933 ev for cu 2p 3 2 prior to the measurement by the electron spectroscopy chemical analysis each of the internal oxidized.