Microstructure Formation Mechanism for Ca(Zr,Hf) | Chapter 4 | Chemical and Materials Sciences: Research Findings Vol. 4

The binary phase diagram of ZrO2-CaO includes the eutectic of the CaZrO3 phase and the CaO-stabilised ZrO2 phase. In this study, Ca(Zr_1-xHfx)O3/(Zr_1-xHfx)O2 (x=0, 1/3, 0.5) eutectic film was prepared by rapid solidification process using high power laser irradiation method. CaCO3 of 99.9% purity, ZrO2 and HfO2 of 98% purity powders were used as starting materials. The coating process was performed in an electric furnace at 1300°C. Solidified film with fine lamellar structure was obtained. When the Zr site was substituted with Hf, the lamellar spacing increased with the amount of substitution. Separate from the solidification film prepared by laser irradiation, a rapidly solidifying sample with x=0.1 composition was prepared using an optical floating zone apparatus. The melt of the sample was free-falling onto a copper dish. No film-like rapidly solidified sample was obtained. Hf ion was homogeneously solid-soluble in both phases of CaZrO3 and ZrO2. This study attempted to prepare eutectic solidification coatings for CaHfO3/HfO2 eutectic under the same conditions as for CaZrO3/ZrO2 eutectic coatings. No eutectic structure was obtained.

 

Author (s) Details

Shunkichi Ueno
College of Engineering, Nihon University, Koriyama, Fukushima 963-8642, Japan.

Please see the book here:- https://doi.org/10.9734/bpi/cmsrf/v4/5468

Early-Stage Precipitation in Al-Li, Al-Cu, Al-Li-Cu and Complex Al Alloys Using Atom Probe Tomography | Chapter 8 | Chemical and Materials Sciences: Developments and Innovations Vol. 8

Aluminum-based alloys play a key role in modern engineering and are widely used in construction components in aircraft, automobiles and other means of transportation due to their lightweight and superior mechanical properties. Additions of Li and/or Cu to Al have been identified as an efficient strategy to improve the strength in age-hardenable or heat-treatable Al alloys via the precipitation hardening phenomenon. The introduction of different nano-structure features can improve the service and the physical properties of such alloys. An improvement of an Al-based alloy has been performed based on the understanding of the relationships among compositions, processing, microstructural characteristics and properties. Knowledge of the decomposition process of the microstructure during the precipitation reaction is particularly important for future technical developments. The first objective of this study is to investigate the nano-scale chemical composition in the Al-Cu, Al-Li and Al-Li-Cu alloys during the early stage of the precipitation sequence and to describe whether this compositional difference correlates with variations in the observed precipitation kinetics. Al-Li-Cu alloys typically exhibit high strengths and good mechanical properties. Investigation of the fine-scale segregation effects of dilute solutes in aluminum alloys which experienced different heat treatments by using atom probe tomography has been achieved. The results show that an Al-1.7 at.% Cu alloy requires a long ageing time of approximately 8 h at 160˚C to allow the diffusion of Cu atoms into the Al matrix. For the Al-8.2 at.% Li alloy, a combination of both the natural ageing condition (48 h at room temperature) and a short artificial ageing condition (5 min at 160˚C) induces increasing in the number density of the Li clusters and hence increases the number of precipitated particles. Applying this combination of natural ageing and short artificial ageing conditions onto the ternary Al-4 at.% Li-1.7 at.% Cu alloy induces the formation of a Cu-rich phase. Increasing the Li content in the ternary alloy up to 8 at.% and increasing the ageing time to 30 min resulted in the precipitation processes ending with δ' particles. To achieve the second objective of this study, a complex and industrial Al alloy AA2195 has been selected and characterized by atom probe tomography. Applying plastic deformation on such alloy has been highlighted as an important engineering tool for manipulation with second-phase precipitates in the microstructure. The findings of the characterization analysis were translated to construct a robust microstructure with an excellent hardness behavior (hardness value of 209 HV) by applying a low-energy-consumption, cost-effective method. The results obtained in this chapter prove the possibilities for the development of specially optimized alloys by obtaining a deep comprehension of the involved microstructural processes.

 

Author (s) Details

 

Muna Khushaim
Department of Physics, Faculty of Science, Taibah University, P. Box: 30002, P. Code 41447, Al-Madina, Saudi Arabia.

Please see the book here:- https://doi.org/10.9734/bpi/cmsdi/v8/3405