Advances in Multi-Principal Elements Alloys X: Alloy Development and Properties: On-Demand Poster Session
Sponsored by: TMS Functional Materials Division, TMS Structural Materials Division, TMS: Alloy Phases Committee, TMS: Mechanical Behavior of Materials Committee
Program Organizers: Peter Liaw, University of Tennessee; Michael Gao, National Energy Technology Laboratory; E-Wen Huang, National Chiao Tung University; Jennifer Carter, Case Western Reserve University; Srivatsan Tirumalai; Xie Xie, FCA US LLC; Gongyao Wang, Globus Medical

Monday 8:00 AM
March 14, 2022
Room: Advanced Materials
Location: On-Demand Poster Hall

Micro-mechanical Properties and Plastic Deformation Behavior of Refractory Low-to-High-entropy Alloys at Different Temperatures: Ping-Hsu Ko1; Yuan-Tao Hsu1; Chi-Huan Tung1; Shou-Yi Chang1; 1National Tsing Hua University
    For application to aerospace industry, refractory high-entropy alloys have been intensively developed. Their microscale mechanical properties and plastic deformation behavior at different temperatures are worth further investigations for understanding the defect activities and mechanical reliability in severe operation conditions. Hence in this study, the mechanical properties and plastic deformation of refractory low-entropy W, medium-entropy WTaMo and high-entropy WTaMoNbV alloys were examined by using single-grain (100 and 111 oriented) nanoindentation and micropillar (100 oriented) compression at 80 to 300C. The hardness and yield strength of the alloys decreased with increasing temperature, while the high-entropy alloy was much softening resistant. The low- and medium-entropy alloys exhibited obvious plastic anisotropy with varied hardness in different orientations and clear long dislocation slips. By contrast, the high-entropy alloy deformed much uniformly with small slips and a high work hardening rate owing to the short-range motion and active double cross slips of small dislocation loops.

Plastic Deformation and Defect Recovery of NiTi-based B2-phase High-entropy Intermetallic Compounds: Ya-Jing Lee1; Ting-Ying Shih1; Cheng-Yuan Tsai1; Chi-Huan Tung1; Shou-Yi Chang1; 1National Tsing Hua University
    High-entropy intermetallic compounds have been developed in recent years to overcome the strength-ductility trade-off of engineering alloys. However, the activities of defects in high-entropy intermetallic compounds remain unclear because of their complex configurations and lattice distortions. In this study, the mechanical properties, plastic deformation and defect recovery of NiTi-based, ordered B2-phase high-entropy intermetallic compound were hence investigated by using nanoindentation and micropillar compression. Experimental results indicated that a higher temperature led to a lower hardness/yield strength and more long dislocation bursts/slips, whereas a lower strain rate caused a lower hardness/yield strength but more short dislocation bursts/slips owing to strain rate sensitivity (0.006 at room temperature and 0.017 at 300°C). At a high temperature and a low strain rate, as well as verified by cyclic micropillar compression tests, defect recovery (rejuvenation) was found to cause a dropped yield stress, a reduced strain hardening rate and improved plasticity.

Study of the Nitriding Behavior of an Austenitic High Entropy Alloy Powder: Mathieu Traversier1; Emmanuel Rigal2; Pierre-Eric Frayssines2; Xavier Boulnat3; Franck Tancret4; Jean Dhers5; Anna Fraczkiewicz1; 1CNRS Lgf Umr5307 Mines Saint-Etienne; 2CEA/LITEN; 3INSA Lyon, MATEIS; 4Université de Nantes, IMN; 5FRAMATOME
     Austenitic single phase HEA from CoCrFeMnNi family usually have low yield strength. Among the numerous ways of strengthening the matrix, nitrogen alloying seems to be promising as it does not only improve the mechanical properties but also enhances the FCC phase stability. In this study, nitriding of gas-atomised powders was studied and two alloys were investigated: the so-called Y3 HEA (CrFeMnNi family) and 304L steel, as the reference material. Nitriding kinetics was monitored by Thermo-Gravimetric Analysis. The evolution of the microstructure during the experiment was investigated through SEM, TEM and XRD analysis.Massive amount of nitrogen (up to 4 wt. %) can be introduced in those alloys. Two families of precipitates, Cr2N and CrN, have been identified, as predicted by thermodynamic simulations. Nitriding kinetics seems to be solely dependent on the powder’s size. HIP densification was also performed to characterise the final mechanical properties of those alloys.

Friction Stir Processing of Non Equiatomic High Entropy Alloy: Neelam Meena1; Satya Dommati2; Vinay Deshmukh2; Nithyanand Prabhu1; 1IIT BOMBAY; 2Naval Materials Research Labroatory
     It has been shown recently that by suitably tuning the composition and designing the microstructure, it is possible to incorporate multiple strengthening mechanisms in a single alloy. Friction stir processing is a severe plastic deformation method. Depending on the process parameters and the thickness of the processed sheet, different grain sizes may be obtained. In the present work, the recently developed TWIP-TRIP assisted dual phaseFe49.5Mn30Co10Cr10C0.5 high entropy alloy is subjected to onep-pass and multi-pass friction stir processing. The friction stir processed samples are tensile tested at different temperatures & strain rates. The obtained results are analysed and compared with that of a sample subjected to cold reduction. A two-fold increase in the yield strength and ductility can be mainly attributed to increased grain boundary/ twin boundary area per unit volume contributing to the Hall-Petch effect and enhanced strain hardening.

Effect of Fe Contents on Plane Stress Fracture Toughness of Fex(CoCrMnNi)100-x High Entropy Alloys at Cryogenic Temperature: Sangeun Park1; Nokeun Park2; Im Doo Jung3; Jae Bok Seol1; Jung Gi Kim1; Hyokyung Sung1; 1Gyeongsang National University; 2Yeungnam University; 3Ulsan National Institute of Science and Technology
    Fe addition and light-weight design is highly effective to expand the application field of high entropy alloys (HEAs). Meanwhile, stacking fault energy is decreased with increasing Fe contents, thus governing deformation mechanism is changed from twinning induced plasticity (TWIP) to transformation induced plasticity (TRIP). As the thickness of HEAs decreases, plane stress fracture toughness test is necessarily required to evaluate the properties of thin plate. In this study, plane stress fracture toughness of Fex(CoCrMnNi)100-x (x = 20, 40, 60 wt.%) alloys are evaluated at cryogenic temperature. In the Fe40 specimen, crack growth is blocked by the twins as well as ε-martensite. While in the Fe60 specimen, a large amount of α'-martensite is transformed, cracks cannot propagate through α'-martensite. The deformation twin and transformed martensite in front of crack tip aid to interrupt crack growth in HEAs leading to severe crack blunting at cryogenic temperature.