Aluminum Alloys, Processing and Characterization: Solidification Microstructure and Processing
Sponsored by: TMS Light Metals Division, TMS: Aluminum Committee
Program Organizers: Andre Phillion, McMaster University; Dmitry Eskin, Brunel University
Tuesday 8:00 AM
March 1, 2022
Room: 208B
Location: Anaheim Convention Center
Session Chair: Jiawei Mi, University of Hull
8:00 AM
Understanding Pre-solidified Grains in Structural Castings of Nemalloy HE700 Experiments: Talha Aziz1; Andre Phillion1; Sumanth Shankar1; Kumar Sadayappan2; 1McMaster University; 2CanmetMaterials
A new family of cast Al-Fe based eutectic alloy system with Zn and Mg as strengtheners through precipitation has been developed and validated for use in structural automotive applications. High vacuum high pressure die casting (HV-HPDC) was used in the casting of structural plates using the Nemalloy HE700 alloy. Typically, HPDC cast components exhibit anomalously large grains in the cast microstructure termed as pre-solidified grains (PSG). These PSG did not present themselves as a critical defect until structural castings were manufactured with this process route. The PSGs in the as-cast microstructure shall be characterized through quantitative metallography and the effects of varying shot interval delays shall be presented.
8:25 AM
High Speed Observations of Ultrasonic Fragmentation and De-agglomeration Process of Free-floating Intermetallics and Oxide Particles: Abhinav Priyadarshi1; Tungky Subroto2; Koulis Pericleous3; Dmitry Eskin2; John Durodola1; Iakovos Tzanakis1; 1Oxford Brookes University; 2Brunel University London; 3University of Greenwich
The need for lightweight and high-strength advance materials in the form of metal-matrix composites with micron-sized particulate reinforcements has received considerable attention within automotive and aerospace industry. Ultrasonic melt treatment of Al-alloys offers a sustainable and eco-friendly approach to produce structural refinement through enhanced heterogeneous nucleation obtained from combined effect of sono-fragmentation of primary intermetallic/dendrites and de-agglomeration of non-metallic oxides/inclusions. However, owing to complexity of the process, understanding of the underlying mechanisms behind these effects is still rudimentary and lacks experimental evidences. In this paper, we shed light to the governing mechanism of fragmentation and de-agglomeration of Al3Zr and MgO particles, respectively in water. Real-time high-speed imaging was performed to discern the dynamic interaction of cavitation with free-floating particles in a controlled ultrasonic environment. In-situ observations revealed that intermetallic breakage primarily occurs due to propagating shock waves, whereas the oxide de-agglomeration happens through microbubble cluster collapses close to the agglomerate.
8:50 AM Invited
Machine Learning Enhanced Synchrotron X-ray Tomography Analysis of the Convoluted 3D Fe-rich Intermetallic Phases in a Recycled Al Alloy: Zhiguo Zhang1; Ling Qin1; Jiawei Mi1; 1University of Hull
Fe-rich intermetallic phases in Al alloys often exhibit complex and 3D convoluted structures and morphologies. In this study, we used synchrotron X-ray tomography to study the true 3D morphologies of the Fe-rich phases in an as-cast recycled Al alloy. Machine learning based image processing approach was used to recognize and segment the different phases in the 3D tomography image stacks. In the studied condition, the β-Al9Fe2Si2 and ω-Al7Cu2 are found to be the main Fe-rich intermetallic phases. The β-Al9Fe2Si2 phases exhibit a spatially connected 3D network structure and morphology which in turn control the 3D spatial distribution of the Al2Cu phases and the shrinkage cavities. The Al3Fe phases formed at the early stage of solidification affects the structure and morphology of the subsequently formed Fe-rich intermetallic phases. The machine learning method has been demonstrated as a powerful tool for processing big datasets in multidimensional imaging-based materials characterization work
9:15 AM Break
9:30 AM
Al-Mg2Si-Mg Alloys: Microstructure and Mechanical Properties from High Pressure Die Casting to Additive Manufacturing: Hailin Yang1; Jianying Wang1; Xixi Dong2; Shouxun Ji2; Eric Nyberg3; 1Central South University; 2Brunel University London; 3Kaiser Aluminum Trentwood
The requirements of light-weighting structures in automotive industry and other transport applications drive the improvement of mechanical properties of aluminium alloys in different manufacturing processes. The present study uses a comparison approach to investigate the microstructure and mechanical properties of an Al–Mg2Si–Mg alloy processed by HPDC and SLM 3D printing. The processing condition, alloy composition, microstructure characterization and mechanical properties under as-cast condition and under as-SLMed condition were introduced in the paper. The strengthening mechanism and the improvement of mechanical properties in comparison with the conventional cast Al-Si-Mg alloys are discussed in association with defect formation.
9:55 AM
Phase Transformation and Microstructure Evolution of Al-Mn Alloy Made by Laser Additive Manufacturing: Qingyu Pan1; Monica Kapoor2; Sean Mileski2; John Carsley2; Xiaoyuan Lou1; 1Auburn University; 2Novelis Global Research and Technology Center
While additive manufacturing (AM) provides opportunities to produce net-shape components for Al alloys, the microstructural evolution and phase transformation during AM and post-AM heat treatment was still not fully identified. In the present work, AA3104 alloy was fabricated by laser direct energy deposition (DED). The fast cooling and repeated thermal cycle during deposition resulted in different phase transformation behavior as compared to conventional DC-cast alloys. The nucleation and growth of constituent phase particles during AM were both sensitive to AM parameters (laser power, scan speed, hatch space, layer thickness) and the thermal property of substrate. In-process thermal history, mainly the reheating effect caused by subsequent layer fabrication, dominated the constituent particle phase transformation and distribution, resulting in a larger amount of α-Al (Fe,Mn)-Si particles in as-built material as compared to as-cast counterpart. Epitaxial grain growth by laser solidification promoted large columnar grains (a few hundred micrometers) along the build direction.
10:20 AM Cancelled
Growth Morphology of Nodular Primary Silicon in Hypereutectic Al-Si Alloy and Growth Mechanism: Ruyao Wang1; Weihua Lu1; 1Institute of Materials Science and Engineering, Donghua University,
Microstructure of nodular primary silicon crystal in hypereutectic Al-Si alloy has been metallographically studied. Etched growth traces were used to investigate the growth mechanism of nodular silicon crystal. Silicon nodule as an equiaxed polyhedron faced with different high index facets grew in concentric growth mode with almost equal growth rate of growth facets. However, the unequal growth rates between two neighboring facets caused the new high index facet to appear, making Si crystal more roundish. The reason for the formation of nodular silicon crystal with multifacets is discussed in terms of the discrepancy of diffusion rate of silicon atoms in melt and crystallization rate of silicon grain with changes in temperature. In current study the high cooling rate in freezing of Al-14wt%Si alloy casting treated by the designed modifier consisting of P, Ti, B and mischmetal (RE) near the chill mould promotes the occurrence of silicon nodule.