Session Overview |
Thursday, May 23 |
10:30 |
Machine learning design of biodegradable Zn alloys and topological design of Zn scaffolds
* Lu-Ning Wang, University of Science and Technology Beijing, China (People's Republic of) Zhang-Zhi Shi Shi, University of Science and Technology Beijing, China (People's Republic of) Yageng Li, University of Science and Technology Beijing, China (People's Republic of) A machine learning model is established to predict properties of biodegradable Zn alloys. A series of Zn alloys with ultimate tensile strengths over 400 MPa and immersion corrosion rates at 50'100 'm/year are designed with high efficiency, with prediction error below 10%. Effects of topological designs on mechanical properties and degradation profile of Zn scaffolds are investigated through both experimental and computational approaches. The results underscore the potential of topological design as a compelling strategy for tailoring performance of additively manufactured Zn scaffolds, thereby advancing their suitability as precise bone substitutes. |
11:00 |
Resorbable PLA-coated Zn-1.5Mg scaffolds - Processing
* Heinz Palkowski, TU Clausthal, Germany Mitja Petri, University of Ljubljana, Slovenia Primo Mrvar, University of Ljubljana, Slovenia Stephane Mery, TU Université de Strasbourg, France Adele Carradó, Université de Strasbourg, France This study deals with casting and forming of open structured Zn-1.5Mg scaffold alloys, coated and filled with polylactic acid (PLA), for their potential application in tissue engineering scaffolds. By changing the ratio between metal and polymer triggering the corrosion rate of such biocompatible compounds should be possible. Open porous Zn-1.5Mg alloy rod scaffolds of size approx. 200 x 25 mmØ were vacuum cast in combination with a salt leaching technique. To produce the NaCl structure, crystals of size 1 – 1.5 mm were sintered first with a sufficient gap size to be filled with the alloy afterwards. This quite big size has to be used to be able to infiltrate the alloy in a sufficient and complete way with the drawback of the need to reduce the rod diameter finally to a size of few mm. Forming tests at RT and under elevated temperatures stated the possibility to reduce the size of the rod - with the salt or the polymer inside - to some mm without fracture of the alloy bridges, so to produce samples in wire dimension or even as flat parts. Tests necessary to determine the boundary conditions concerning infiltration limits or deformation limits for PLA-filled samples are pending. This study underscores the feasibility of shaping PLA-coated Zn-1.5Mg scaffolds. The brittle structure of NaCl at the surface makes necessary a metallic coat to avoid breakouts of the salt and therewith early fracture of the alloy. This close metallic cover is detrimental to the process of removing the salt as well as filling with the polymer. |
11:15 |
Effect of alloying and PMMA grafting on the biodegradation performance of Zn-Mg hypoeutectic alloys
Alia A. Diaa, Design and Production Engineering Department, Faculty of Engineering, Ain Shams University, Cairo 11517 Nahed El-Mahallawy, Design and Production Engineering Department, Faculty of Engineering, Ain Shams University, * Adele Carrado, CNRS IPCMS, France Extruded pure zinc (Zn) and two hypoeutectic Zn-Mg alloys, with 0.68 and 1.89 wt.% Mg content, were prepared. A polymethyl methacrylate (PMMA) layer of about 2.1 ± 0.4 µm thick was applied to the alloys by the "grafting-from” technique to mitigate the alloys’ in-vitro biodegradation rate. The potentio-dynamic corrosion test showed that the corrosion current density of pure Zn increases with alloying and continues to increase as the Mg content increases. PMMA grafting was capable of decreasing the corrosion current density of Zn-0.68 Mg to a value lower than that of pure Zn, while this did not work for the Zn-1.89 Mg alloy. The immersion test was carried out to assert the effect of alloying and PMMA grafting. |
11:30 |
Understanding microstructure-texture-property relationships in low-alloyed zinc - key to controlling biodegradability
* Magdalena Bieda-Niemiec, Institute of Metallurgy and Materials Science of Polish Academy of Sciences, Krakow, Poland, Poland Magdalena Gieleciak, Institute of Metallurgy and Materials Science of Polish Academy of Sciences, Krakow, Poland Anna Jarzebska, Institute of Metallurgy and Materials Science of Polish Academy of Sciences, Krakow, Poland Weronika Gozdur, Institute of Metallurgy and Materials Science of Polish Academy of Sciences, Krakow, Poland Elwira Rusinek, Institute of Metallurgy and Materials Science of Polish Academy of Sciences, Krakow, Poland Lukasz Maj, Institute of Metallurgy and Materials Science of Polish Academy of Sciences, Krakow, Poland Lukasz Rogal, Institute of Metallurgy and Materials Science of Polish Academy of Sciences, Krakow, Poland Mariusz Kulczyk, Institute of Metallurgy and Materials Science of Polish Academy of Sciences, Krakow, Poland * Jacek Skiba, Institute of Metallurgy and Materials Science of Polish Academy of Sciences, Krakow, Poland Bioabsorbable metals such as magnesium, iron, zinc and lately molybdenum have been investigated intensively in the last decades as an excellent alternative for permanent implants produced from titanium, stainless steel, etc. An important question that needs to be addressed in the development of metallic biodegradable implants is how the changes in microstructure influence the other important factors i.e.: mechanical properties and corrosion rate. Providing the appropriate combination of properties is critical. Lately, zinc has gained attention for its optimal corrosion rate and biocompatibility, making it a promising candidate for various implant applications. However, pure zinc has a low melting point and low mechanical properties. Zinc possesses HCP (hexagonal closed packed) crystal structure and a limited number of slip systems and twinning possibilities it is difficult to improve its properties using classical plastic deformation methods. Moreover, pure zinc recrystallizes at room temperature, which influence the stability of the deformed structure and provokes strong dynamic recrystallization processes during deformation. In the literature, many investigations are focusing on adding different alloying elements and using different deformation methods in order to meet the requirements. Most of them are not optimal, there are several issues concerning mechanical properties that are worth noticing like e.g.: work softening , static recrystallization and aging at room temperatures. Most of the researchers focus on the characterization of the new material. Nevertheless, there is a lack of fundamental studies which are describing the influence of microstructure on the mechanical and corrosion behavior for zinc and its alloys. To fill that gap, investigations of the low alloyed zinc after plastic deformation were performed. It was shown that a proper combination of grain size, texture and distribution of second phase particles could provide uniform biocorrosion and good mechanical properties of the zinc alloys. The innovative approach covers fundamental studies that could provide a direction for uniform degradation, assuring a good response of the human body to corrosion products. These properties are crucial for the application of zinc alloys as bioabsorbable implants. |
11:45 |
TBC
TBC |
12:00 |
Discussion on morning session presentations
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