Controlled Generation Of Ferromagnetic Martensite From Paramagnetic Austenite In Aisi 316l Austenitic Stainless Steel

摘要

The strain-induced austenite (γ) to martensite (α') transformation in AISI 316L austenitic stainless steel, either in powders or bulk specimens, has been investigated. The phase transformation is accomplished using either ball-milling processes (in powders)-dynamic approach-or by uniaxial compression procedures (in bulk specimens)-quasi-static approach. Remarkably, an increase in the loading rate causes opposite effects in each case: (ⅰ) it increases the amount of transformed α' in ball-milling procedures, but (ⅱ) it decreases the amount of α' in pressed samples. Both the microstructural changes (e.g., crystallite size refinement, microstrains, or type of stacking faults) in the parent γ phase and the role of the concomitant temperature rise during deformation seem to be responsible for these opposite trends. Furthermore, the results show the correlation between the γ → α' phase transformation and the development of magnetism and enhanced hardness.