Synthesis and characterization of austenitic stainless steel by mechanical alloying

In the present study, an attempt on synthesis of austenitic stainless steel powder with nominal composition 70Fe-18Cr-8Ni (all in wt %) was milled by using planetary ball mill from 0 to 40 h. The 40 h milled powder was dispersed with 1.0 wt% nano-Y2O3 particles through blending and subsequently consolidated by conventional sintering at 1150°C for 1 h. The phase evolution and microstructure characterization at each stage of milling of 0h, 1h, 5h, 10h, 15h, 20h, 30h, 40h of the current alloys during milling were studied by using X-ray diffraction (XRD) and scanning electron microscope (SEM). The transformation of phase depends upon the milling time. With the increase of milling time, the intensity prominent peaks of XRD gradually decreases and peak broadening occurs. During the milling operation from 0h to 40h, the elements like Fe, Ni and Cr goes into the solid solution which increases the residual strain of the grains and decreases the crystal size of the particles. The crystallite size of austenitic stainless steel changes from 63.6ìm to 5.49ìm after 40 hours of milling. The sintering product, have been evaluated for determining different physical property (density and porosity) and mechanical property (hardness). It is found the hardness of alloy with dispersion of 1.0 wt% nano-Y2O3 particles was increased by 1.5 to 2 times higher than that of austenitic alloys