Z phase in austenitic chromium-manganese steel containing nitrogen and niobium

The authors have devised a method of isolating and analyzing the Z phase in chromium-manganese steel alloyed with nitrogen and niobium having the following % composition: 0.06 - C; 17.6 - Cr; 17.8 - Mn; 0.34 - Si; 0.25-Nb; 0.14 - Mo; 0.4 - N. The presence of the Z phase was confirmed by electron diffraction and isolated electrochemically. X-ray patterns recorded after all the stages in the chemical treatment showed that the acid and alkali treatments dissolved the carbides while leaving the Z phase undissolved. The following mass % composition was thus found for the Z phase in this steel: 24.3 Cr; 11.0 Fe; 8.0 Mn; 52.8 Nb; 0.3 Mo; 2.8 N. By comparison with the average composition of the steel, the phase is enriched in chromium, niobium, and nitrogen, being a compound chromium-niobium carbide including other alloying elements.