Microstructural Evolution and Mechanical Properties of Nano-Yttria Dispersed 316 L Austenitic Stainless Steel by Mechanical Alloying and Sintering

Abstract

Composite powders of pre-alloyed 316 L austenitic stainless steel with yttria (Y2O3) powder in various compositions (0.3, 1.0, 1.5 and 2 wt%) were synthesized by mechanical alloying using a high energy ball mill. The 25-h milled powder has shown no changes other than exhibiting an austenite phase of FCC (a = 3.54 Å) structure. Milled powders were found to contain nano-yttria dispersed in the austenitic stainless steel matrix of nano-crystallite size and with high lattice strain. Milled powders were cold pressed and sintered at 1100 °C (1373 K) in a controlled atmosphere. It can be inferred that nano-yttria dispersion restricts grain growth of matrix even during conventional sintering. The present yittria dispersed austenitic alloy showed the low physical density and increase in compressive strength (194–374 MPa) and hardness (477–528 HV). The compressive strength and hardness enhancement can be attributed primarily to the dispersoids of nano-yttria in the austenitic matrix by dispersion strengthening/hardening mechanisms. © 2021, The Indian Institute of Metals - IIM.