Crystalline characteristics of a dual-phase precipitation hardening stainless steel in quenched solid solution and aging treatments

Abstract

This study investigated the development of the microstructures and aging reactions in a new dual-phase (allotriomorphic 8 + gamma) 17-4 precipitation-hardened (PH) stainless steel (SS) alloy. The 17-4 PH alloy, a martensitic stainless steel containing Cu (3-5 wt.%), was subjected to solid solution treatment followed by quenching using oil, H2O, or liquid N2. The microstructures of the steel specimens were primarily composed of lath martensite and allotriomorphic 8-ferrite. X-ray diffraction analysis indicated that the structures consisted entirely of bcc phase peaks. During aging at 560 and 600 degrees C, the local microstrain was released because of the tempering of the lath martensite and the formation of reverted austenite, resulting in a shift in the kernel's average misorientation distribution toward lower angles. The misorientation associated with the martensite boundaries ranged from 10 degrees to 20 degrees and from 47 degrees to 57 degrees in the packets. In the blocks, it ranged from 50 degrees to 60 degrees. The F1-ferrite approximately followed the Kurdjumov-Sachs orientation relationship with A1-austenite and A2-austenite.