Advancements in Steel Structural Refinement: Advancements in Steel Structural Refinement
Sponsored by: AIST: Metallurgy—Processing, Products and Applications Technology Committee
Program Organizers: Charles Enloe, Steel Dynamics; Emmanuel De Moor, Colorado School of Mines; Jianfeng Wang, General Motors Global Research and Development; Jose Rodriguez-Ibabe, RIcon; Steven Jansto, Research and Development Resources
Monday 10:00 AM
October 18, 2021
Room: A211
Location: Greater Columbus Convention Center
10:00 AM
Maximizing Strengthening Mechanisms in Continuously-annealed HSLA Steel: Charles Enloe1; Fabio D'Aiuto2; Hardy Mohrbacher3; 1CBMM North America; 2CBMM Europe; 3NiobelCon bvba
Well-established practices exist for production of cold-rolled and continuously-annealed high strength low alloy (HSLA) steels as both coated and uncoated variants. Through utilization of standard processing techniques, the yield strength of cold-rolled HSLA steel is practically limited by numerous process and alloy design factors to 550 MPa and less. A production methodology is proposed to achieve greater strengths in cold-rolled and continuously annealed HSLA steels. This methodology utilizes both increased precipitation of microalloy carbides prior to continuous annealing and a subsequent annealing process in which recrystallization of ferrite is successfully suppressed prior to partial or full austenitizing. The resultant microstructure, as a consequence of enhanced precipitate and grain refinement strengthening, achieves greater strengths than those traditionally produced for automotive application of cold rolled HSLA steels. The implications of mass adoption of such enhanced cold-rolled HSLA steels are discussed - including the potential for partial replacement of intermediate strength AHSS.
10:30 AM
Microalloyed Steel Precipitate Characterization by Automated TEM Image and EDS Analysis: Roger Maddalena1; 1Thermo Fisher Scientific
Nanoscale precipitates in steel are known to affect properties by grain refinement and precipitation hardening. One of the challenges is to obtain a statistically meaningful distribution of their size, shape and composition as up to now this has only been possible with tedious, manual analysis. In this study an electron microscopy workflow is presented where the acquisition of images and chemical information is fully automated, even for overnight analysis on large area samples. Preparation techniques including carbon replica, electropolishing and focused ion beam will be compared, where the latter two methods create an electron transparent region that maintains orientation of precipitates relative to the grain boundaries.Instead of characterizing 20 or 30 precipitates per day manually, the automated TEM can process more than 500 precipitates per hour for a typical sample. The actual throughput depends on the number of particles per unit area.
11:00 AM
The Capability of Severe Plastic Deformation to Achieve High Strength and Toughness in Two High Strength Steel Alloys, Austenitic FeMnAl and Martensitic AF9628: Matthew Vaughan1; Sezer Picak1; Cafer Acemi1; Richard Harris2; Peyman Samimi1; Sean Gibbons2; Rachel Abrahams2; Robert Barber1; Ibrahim Karaman1; 1Texas A&M University; 2Air Force Research Laboratory
The effects of equal channel angular pressing (ECAP) to refine the microstructure in high strength steel alloys is explored. The alloys analyzed are FeMnAl, an austenitic steel alloy known for its high strength to weight ratio due to the addition of Al, which reduces weight and increases precipitation hardenability; and AF9628, which is a newly developed high strength low alloy (HSLA) martensitic steel alloy known for exceptional strength and toughness. Given the high strength of these materials, processing via ECAP could only be achieved at high temperatures (>900°C). However, despite high processing temperatures, these materials achieved significant strengthening after ECAP via microstructural refinement. Here, the number of imposed ECAP passes, the selected routes, and the selected temperatures of processing produced a variety of enhancements in mechanical properties for these materials, allowing for a fairly thorough exploration of the limits of the mechanical property space for FeMnAl and AF9628 steel alloys.