Steels and High Entropy alloys

Project Description

Steels and high entropy alloys are very important engineering materials. Understanding the phase separation and seggregation mechanisms in these alloys is extremely complex. And controlling them is even more challenging. However, it is critical to evaluate and understand the thermodynamics of these alloys. In this project, we have designed several thermo-mechanical treatments and characterization routines to understand the influence of various material defects and their interactions with wide range of alloying elements used in these materials.

Related Publications

• "Current Challenges and Opportunities in Microstructure-Related Properties of Advanced High-Strength Steels" - Metallurgical and Materials Transactions A Sept 2020. View Publication
  This viewpoint paper reviews recent advances in understanding the microstructure–property relationships of advanced high-strength steels (AHSS), focusing on Mn-containing alloys with complex deformation mechanisms like twinning, transformation, and nanoprecipitation. It critically examines their microstructures, mechanical performance, and resistance to damage such as hydrogen embrittlement. The paper also highlights progress in characterization, modeling, and emerging fields like machine learning and additive manufacturing.
• "Dislocation exhaustion and ultra-hardening of nanograined metals by phase transformation at grain boundaries." - Nature Communication Jan. 2022. View Publication
  This study demonstrates that nanograined Fe-Ni metals with grain sizes in the tens of nanometers can achieve ultra-high strength through dislocation exhaustion, rivaling even finer-grained metals. Intergranular Ni enrichment triggers grain boundary phase transformations at low temperatures, which deplete lattice dislocations. As a result, plasticity is governed by grain boundary dislocation sources, enabling an ultra-hardening effect. This offers a new strategy for designing strong nanometals via grain boundary engineering.
• "Grain boundary segregation induced precipitation in a non equiatomic nanocrystalline CoCuFeMnNi compositionally complex alloy" - Acta Materialia Nov. 2021. View Publication
  This study investigates phase evolution in a non-equiatomic nanocrystalline CoCuFeMnNi alloy using in-situ TEM heating, ACOM, EFTEM, and APT. It reveals a complex sequence of grain boundary segregation and depletion, leading to FeCo-rich B2 precipitate formation with specific orientation relationships. Cu, Ni, and Co segregate early, while Fe and Mn deplete, followed by Mn segregation after precipitation onset. The high grain boundary density in the nanocrystalline state plays a critical role in enabling these transformations, unlike in coarse-grained counterparts.