The Effects of Al and C Content on the Microstructure, Ms Temperature and the Mechanical Properties in 17Cr-7Ni Stainless Steel

Abstract

In order to make clear the roles of Al and C in 17Cr-7Ni stainless steel, the microstructural features, Ms temperature, and mechanical properties were investigated for the steels containing variable amounts of Al and C. The results obtained are as follows:
(1) The quantity of δ-ferrite in matrix increased with the increase of Al content, or the decrease of C content. No δ-ferrite is observed in the range of Al content less than about 0.7%, but the phase of δ-ferrite is nearly 10 and 50% in matrix for steels containing about 1 and 2% Al, respectively. Furthermore, for the steels containing about 0.01 and 0.07% C, the phase of δ-ferrite exists in 45 and 10% in matrix, respectively. And also when C content in steel is more than 1%, the δ-ferrite can not be observed.
(2) According to our experiments, it seems that the Ms temperature is raised in rate of 20°C per 1% Al, and is dropped down about 14°C per 0.01% C in content.
(3) It is confirmed that the microstructural features and the Ms temperature are affected sensitively with Al and C content.
(4) The best mechanical properties is obtained for the steel containing about 1.2% Al and 0.07% C. Also it can be recognized that the age hardenability are increased with the increase of Al content, and with the decrease of C content.