Late News Poster Session: On-Demand Poster Session: Light Metals
Program Organizers: TMS Administration
Monday 8:00 AM
March 14, 2022
Room: Light Metals
Location: On-Demand Poster Hall
Formation of Macroscopic Deformation Band in Porous Metals with Unidirectional Pores: Mahiro Sawada1; Shinsuke Suzuki1; 1Waseda University
Macroscopic deformation bands are often observed during the compression of porous metals. It should be suppressed since it leads to stress drop but where the bands form is yet to be clarified. The objective of this research was to predict the formation of deformation bands from initial pore structure in porous metals with unidirectional pores. A pore structure was prepared which had irregular pore alignment, pore diameter of 3 mm, edge length of 25 mm, and porosity of approx. 35 pct. Theoretical calculation of stress concentration factor in a plate with an infinite row of pores was employed to estimate stress concentration at each cell wall. The deformation band was considered to form at the horizontal stream of cell walls with a relatively high stress concentration factor. The formation was successfully confirmed in the numerical analysis as a continuation of the cell walls with relatively large equivalent plastic strain.
Ultrasonically-induced Microstructural Refinement during Casting of an Al-Si-Mg Alloy: Katherine Rader1; Jens Darsell1; Jon Helgeland1; Nathan Canfield1; Aashish Rohatgi1; 1Pacific Northwest National Laboratory
Ultrasonic melt processing of aluminum alloys is of interest to improve the mechanical properties of cast automotive components through local microstructural refinement. In this study, ultrasonic vibrations were applied during solidification to a commercial Al-Si-Mg alloy cast in a graphite mold. Optical microscopy and electron backscatter diffraction were used to characterize the resultant microstructures with respect to grain size and morphology. Material that was cast without ultrasonication has a coarse dendritic microstructure with a mean grain size of 155 µm and a mean secondary dendrite arm spacing of 23 µm. Material that was ultrasonically modified has a non-dendritic microstructure with two distinct morphologies: (1) globular grains with a mean grain size of 19 µm and (2) highly-refined grains with a mean grain size of 9 µm. These non-dendritic microstructures demonstrate the ability of ultrasound applied during solidification to both refine the microstructure and modify the conventional dendritic morphology.
Effect of Cooling Rate on EN AW 6082 Alloys: Tansu Guven1; Emrah Ozdogru1; Hilal Colak1; 1Tri Metallurgy
EN AW 6082 alloys are used in many different areas from construction to structural applications and from automotive to aerospace industry. Having the highest strength and corrosion resistance in the 6XXX group, EN AW 6082 also has greater weldability, formability and machinability. Since studies on this industrially important alloy the homogenization and cooling are limited. The cooling rate is one of the main factors determining the distribution and density of the precipitates in the grain. Billet samples homogenized for 3 hours at 550˚C and cooled at 50˚C h-1,100˚C h-1 250˚C h-1 500˚C h-1 and 1000˚C h-1 cooling rates, respectively. It is aimed to characterize the precipitates formed with different cooling rates and to observe their behavior. The microstructure difference between the cooling rates were determined. The amount of precipitate increases with decreasing cooling rate. On the contrary, a significant reduction of precipitation was observed at 1000˚C h-1 cooling rate.
Improved Room Temperature Formability of High Strength Al Sheets Using Friction Stir Processing: Hrishikesh Das1; Piyush Upadhyay1; Wahaz Nasim1; Mert Efe1; 1Pacific Northwest National Laboratory
Widespread application of high strength Al sheets is limited primarily due to their poor room temperature formability. Selective microstructural modification can enable formability improvements locally while retaining strength in other areas. Friction stir processing (FSP)method have shown promising results towards this goal. In this poster we will present current progress in local formability improvements using high speed friction stir processing in age hardened automotive Al sheets. Local formability improvements as high as 30% has been shown in 7085-T76 as measured by minimum bend radii (r/t) ratios established with V-bending tests. Comparable results in 7055-T6 alloys will also be presented.