Papers by Keyword: Al-Cu

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Authors: Tatsuo Sato, Shoichi Hirosawa
Abstract: The nano-scale precipitate microstructures and properties of age-hardenable aluminum alloys such as Al-Cu, Al-Mg-Si and Al-Zn-Mg alloys were investigated using conventional electrical resistivity and hardness measurements, TEM and 3D-AP techniques. To increase mechanical strength and ductility of the alloys nano-scale precipitates were effectively controlled by applying new type heat treatments and microalloying elements. In the initial stage of phase decomposition of the alloys containing microalloying elements several types of nanoclusters were formed and distinctly detected by the 3D-AP technique. These nanoclusters greatly affect the nucleation of the subsequent precipitates and resultantly mechanical properties. In Al-Mg-Si and Al-Zn-Mg alloys complicated two-step aging behaviors were found to be originated in the positive or negative effect of the nanoclusters with different structures.
Authors: G. Durrant, Mark Gallerneault, Brian Cantor
Authors: Chun Li Liu, Xiang Yang Liu, Leonard J. Borucki
Authors: Yasuyuki Yoshida, Hisao Esaka, Kei Shinozuka
Abstract: Hot tearing is the one of the biggest problems when casting aluminium alloys. Although there has been much research work in this field, it is still not clear what causes hot tearing and how it propagates. Furthermore, the effect of solidified structure on the hot tearing has not been clear. Therefore, this study has been carried out to correlate the solidified structure and hot tearing. Al-2.0 wt% Cu alloy was used for test alloy. To change the solidified structure, some amount of refiner was added to the molten alloy. A permanent mould, which has been developed by us, can form hot tearing intentionally in the center region of a solidified shell. The cross section of a solidified shell was metallographically investigated and solidified structure and hot tearing were characterized. The length of hot tear decreased with increasing the amount of refiner. This may indicate that it is difficult for hot tear with fine equiaxed grains to propagate. In addition to this, the residual liquid around the hot tear was moved to the cracking due to negative pressure and hot tearing was partially healed.
Authors: Tomoyuki Honma, David W. Saxey, Simon P. Ringer
Abstract: The trace addition of Sn (0.01 at.%) to an Al-1.7Cu (at.%) alloy has been investigated using atom probe tomography (APT), transmission electron microscopy (TEM) and high resolution transmission electron microscope (HRTEM). We have studied samples in the as-quenched (AQ) condition and following ageing at both 160 and 200 °C for very short ageing times so as to better understand the early stages of the decomposition processes. Our data reveal independent Cu-Cu and Sn-Sn clusters in the AQ condition, though we did not observe Cu-Sn clustering. We observed for the first time that some of these initial Cu-clusters develop into GP zones during subsequent ageing at temperatures as high as 200 °C. The Sn atom clustering results in precipitation of independent 􀀂- Sn particles after aging for 30 sec. The GP zones consequently undergo reversion and this liberates Cu atoms which seem to participate in a cluster-assisted heterogeneous nucleation of the 􀀃􀀂 phase at the interface of the 􀀂-Sn. For ageing at 200 °C, this process is complete within 180 sec.
Authors: Shigeru Kuramoto, Keitaro Horikawa, Motohiro Kanno
Authors: Brian M. Gable, Barry C. Muddle
Abstract: The ability to improve mechanical properties through trace alloying additions that enhance the precipitation-hardening response has been a cornerstone of aluminium research and alloy development. It is now known that many of these alloying additions are beneficial (or deleterious) because of their influence on the competitive precipitation kinetics, in many cases arising from the formation of chemical and structural heterogeneities in the matrix. In order to better our understanding of this phenomenon, the earliest stages of microstructural evolution of indium precipitates and θ' plates in an Al-Cu-In ternary alloy have been investigated. Quantitative microstructural characterization reveals that there is a correlation between the size of the pre-existing indium particle and the resulting heterogeneous precipitation kinetics, with larger indium particles favouring θ' precipitation.
Authors: An Na Yue, Kun Peng, Ling Ping Zhou, Jia Jun Zhu, De Yi Li
Abstract: Titanium and aluminum films were deposited on oxygen-free copper substrates by electron beam evaporation method to obtain Al/Cu and Al/Ti/Cu layer composites. Evolution of microstructure and properties of Al/Cu and Al/Ti/Cu thin film during heat treatment processes were investigated by XRD, SEM and electrical properties analysis. The introduce of Ti layer can prevent the formation of Cu-Al intermetallic compounds, and has no obvious influence on the electrical resistivity of Al/Cu thin film, which can be used as a pad in microelectronic package and devices.
Authors: Laure Bourgeois, Timothy Wong, X.Y. Xiong, Jian Feng Nie, Barry C. Muddle
Abstract: The interaction between vacancies and Sn and Cu solute atoms in an Al-1.7at.%Cu- 0.01at.%Sn alloy was investigated by exploring the effect of incorporating natural ageing into conventional age hardening treatment. It was found that provided the artificial ageing temperature does not exceed a critical value between 160°C and 200°C, a narrow window of natural ageing (3-100 h) will result in a significant acceleration of the age hardening response and no decrease in peak hardness. Transmission electron microscopy showed that this effect reflects a large and rapid increase in number density of Cu GP(I) zones, and, to a lesser extent, of θ". The distribution and number density of θ' are essentially unaffected. Three-dimensional atom probe provided strong evidence that refinement of GP(I) zone distribution is not due to clustering of Cu atoms onto pre-existing Sn clusters. Instead it appears to be caused by a subtle interaction between vacancies, Sn and Cu atoms.
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