Development in Light Weight Alloys and Composites: Microstructure and Mechanical Properties
Sponsored by: TMS Composite Materials Committee, TMS Materials Characterization Committee
Program Organizers: Ramasis Goswami, Naval Research Laboratory; Nikhil Gupta, New York University; Aashish Rohatgi, Pacific Northwest National Laboratory; Tanjore Jayaraman, United States Air Force Academy

Wednesday 8:00 AM
October 12, 2022
Room: 403
Location: David L. Lawrence Convention Center

Session Chair: Ramachandra Canumalla, Weldaloy Specialty Processing; Nikhil Gupta, NYU


8:00 AM  Invited
Friction Stir Processing Based Local Microstructure Modification to Improve High-cycle Fatigue Properties of High-pressure Die-cast Aluminum Alloy: Avik Samanta1; Hrishikesh Das1; Glenn Grant1; Saumyadeep Jana1; 1Pacific Northwest National Laboratory
    High-pressure die-cast (HPDC) aluminum alloys can provide a prospective pathway for lightweighting in vehicle industries by replacing structural components with large, thin wall and complex-shaped castings. However, microstructural defects such as shrinkage and gas porosity, entrapped oxide inclusions, etc., in HPDC material results in limited fatigue properties, affecting its prospect as a structural material. Friction stir processing (FSP) has emerged as an efficient technique to locally modify microstructure through severe plastic deformation. In this work, we report enhancement of high cycle fatigue life of HPDC A380 alloy through local FSP induced microstructure modification. High cycle fatigue property is evaluated in a 4-point bending mode configuration at stress ratios of R = 0.1 on through-thickness specimens. A 10-fold improvement in fatigue life is observed over the parent HPDC material after FSP modification. Considering the improvement, mechanisms of fatigue crack initiation and propagation are investigated.

8:30 AM  
Development of Hierarchical Aluminum-based Metal Matrix Composites Using Friction Extrusion: Rajib Kalsar1; Benjamin Schuessler1; Xiaolong Ma1; Jens Darsell1; Tianhao Wang1; Sridhar Niverty1; Lei Li1; Ayoub Soulami1; Vineet Joshi1; 1Pacific Northwest National Laboratory
    Friction extrusion process is a newly developed solid phase processing method and emerging as a potential energy efficient processing method for microstructural modifications to improve various properties, such as mechanical, corrosion and functional. Friction extrusion process has been utilized to develop hierarchical metal matrix composite (MMC) microstructures in Al alloys to improve strength and ductility simultaneously. Ceramic particles (Al2O3) with 5 - 25 vol% were extruded in the form of 5 mm diameter rod to get Al-MMC microstructures. A unique hierarchical composite microstructure is achieved using the process. Quantitative microstructural characterizations were performed using scanning electron microscopy (SEM), back-scatter electron microscopy (EBSD) and transmission electron microscopy (TEM) to understand the distribution of the ceramic particles in the Al-matrix as well as ceramic particle and matrix interactions. Mechanical properties of MMCs were evaluated by performing tensile tests of the extruded rods.

8:50 AM  
Designing Al-Cu Alloy to Improve the Mechanical Properties and Thermal Stability via Micro-alloying with Cr Solute: Gihoon Moon1; Eunkyung Lee1; 1National Korea Maritime and Ocean University
    The refinement and thermal stability of metastable θ' precipitates are critical in the development of new high-performance Al-Cu alloys for elevated temperature applications. In this work, the micro-alloying influences of Cr on the aging behavior and thermal stability of Al-Cu alloy were systematically studied. The results showed that the addition of Cr can increase the strength during artificial aging and effectively improved the thermal stability of θ’ during prolonged thermal exposure. This is because the enhanced precipitation kinetic and microstructural stabilization arise from the segregation mechanism of Cr at the Al/ θ' semi-coherent interfaces. Especially, the Cr-segregation at the interface is essential to improve the coarsening resistance of θ' by acting as a kinetic diffusion barrier. This study reveals how the micro-alloying of Cr solute can work in concert to a stabilization mechanism, and the results provide insights that can be contributed to the design of high-temperature alloy.

9:10 AM  
Development of Functionally Graded Al Metal Matrix Hybrid Composite Reinforced with CNT ,Y2O3 & SiC through PM Route: Rajat Gupta1; Kausik Chattopadhyay1; Nilay Mukhopadhyay1; 1IIT BHU
    In the present study light-weight high strength hybrid reinforced Al metal matrix composite (MMC) is fabricated through powder metallurgy. Effect of CNT ,Y2O3 & SiC reinforcements in Al matrix has been studied to investigate their influence on the structure, morphology, phase composition, thermal stability and mechanical properties. Continuous variation of CNT and Y2O3 (0-2.5 wt%) were done simultaneously to prepare a graded structure upon consolidation. Characterizations were done through XRD, TEM, SEM-EDS and indentation. The milling time of more than 20 hrs leads to uniform distribution of CNT and further cryomilling (CM) with ball to powder ratio of 100:1 reduced its agglomeration along with effective cleaving of nanotubes and reducing the entanglements. XRD analysis shows feasible reaction products that were formed during processing. The CM of MMCs effectively helps in overcoming the problem associated with agglomeration and hybrid graded structure significantly reduces the CTE issues with existing Al based MMCs.

9:30 AM  
Understanding the Influence of Yield Asymmetry on Sheet Metal Bendability of Magnesium Alloys: Sourav Mishra1; Sushanta Panigrahi1; 1Indian Institute of Technology, Madras
    Magnesium and its alloys have a great potential in sheet metal structural components due to their light weighting properties. However, most magnesium sheet metal manufacturing routes involve various extents of bending; wherein the presence of yield asymmetry causes undesirable shifts in neutral axis leading to unpredictable spring back. In the current study, a magnesium alloy was subjected to material processing under several conditions to alter the yield asymmetry properties. The bendability of the processed sheet metals was evaluated by V-Bending forming process and coefficient of neutral axis was derived after the V-Bending operation. The extent of shift in the neutral axis in the Magnesium sheet metals during bending was correlated to the amount of spring-back encountered. The microstructural changes were captured during the V-Bending operation and after the spring-back. The trends in spring back, the shift of neutral axis, and yield asymmetry in processed Mg sheet metal products were established.

9:50 AM Break

10:10 AM  
Recent Developments in Flux-Free Brazing of Aluminum Alloys: Andreas Kulovits1; Harry Zonker1; Michael Danz1; Marvin Goins1; 1Arconic
    Aluminum brazing is a joining technology that uses a low melting point aluminum alloy filler metal that is metallurgically bonded to a higher melting point substrate alloy. During brazing, materials are heated above the melting temperature of the filler metal. Joint formation occurs by capillary action. Challenges during brazing of aluminum alloys constitute the native grown Al2O3 and the wetting behavior of liquid Al. Mass production of heat exchangers in controlled atmosphere brazing furnaces uses a flux to remove Al2O3 and enable surface wetting which degrades internal cleanliness. Drives to electrification of automotive vehicles and fuel cells, require ultraclean cooling systems to avoid performance detriment. Efforts are being undertaken to minimize flux. We will explain requirements for brazing in inert atmosphere with residual oxygen without flux. We introduce the concept of alloying additions to brazing sheet that enable flux-free brazing. The, remaining scientific and engineering challenges will be discussed.

10:30 AM  
Solute Synergy Improved Thermal Stability of Nanotwinned Al Alloys: Nick Richter1; Yifan Zhang2; Mingyu Gong3; Tongjun Niu1; Bo Yang1; Sichuang Xue4; Jian Wang3; Xinghang Zhang1; 1Purdue University; 2Los Alamos National Laboratory; 3University of Nebraska-Lincoln; 4Pacific Northwest National Laboratory
    Nanocrystalline Aluminum (Al) alloys have various engineering applications. However, they often suffer from poor thermal stability due to the large driving force for grain coarsening. In this study, we implement a strategy of solute synergy to simultaneously bolster mechanical strength and thermal stability. Using in-situ micropillar compression testing, it is shown that Zr additions can largely improve the flow stress of nanotwinned Al-Co alloys to 1.3 GPa, while maintaining significant deformability. Zr solutes also promote microstructural and mechanical stability even when annealing up to 400 °C (0.72Tm of Al). Density functional theory calculations uncover the role of Co-Zr solute pairs in pinning and stabilizing incoherent twin boundaries. This work highlights the possibilities for improvement of mechanical strength and thermal stability of nanocrystalline Al alloys when combining solute pairs that possess these synergistic effect.