Investigating the Effect of Heat Treatment on the Microstructure and Hardness of Aluminum-Lithium Alloys.

In this study, the effects of heat treatment on the microstructure and strength (micro-hardness) of an aluminum-lithium (Al-Li) base alloy containing copper (Cu) and scandium (Sc) were investigated, with a view to enhancing the alloy performance for aerospace applications. The heat treatment conditions were investigated to understand the precipitation behavior and the mechanisms involved in strengthening. Aging was carried out at temperatures of 130 °C and 150 °C for aging times of 1 h, 2.5 h, 5 h, 10 h, 15 h, 25 h, 35 h, and 45 h at each temperature for Al-Li alloy and at 160 °C, 180 °C, and 200 °C for aging times of 5 h, 10 h, 15 h, 20 h, 25 h, and 30 h at each temperature for Al-Li-Cu and Al-Li-Cu-Sc alloys. The investigation revealed that both solution heat treatment and artificial aging had a notable impact on strengthening the hardness of the alloy. This effect was attributed to the characteristics of the precipitates, including their type, size, number density, and distribution. The addition of copper (Cu) and scandium (Sc) was observed to have an impact on grain size refinement, while Cu addition specifically affected the precipitation behavior of the alloy. It led to remarkable changes in the number density, size, and distribution of T1 (Al2CuLi) and θ' (Al2Cu) phases. As a result, the hardness of the alloy was significantly improved after the addition of Cu and Sc, in comparison with the base Al-Li alloy. The best heat treatment process was determined as: 580 °C/1 h solution treatment +150 °C/45 h artificial aging for Al-Li alloy and 505 °C/5 h solution treatment +180 °C/20 h artificial aging for Al-Li-Cu and Al-Li-Cu-Sc alloys.

A Review on the Analysis of Thermal and Thermodynamic Aspects of Grain Refinement of Aluminum-Silicon-Based Alloys.

The present analysis addresses the solidification and thermodynamic parameters involved during the solidification of aluminum (Al)-based alloys as presented in the literature using different systems viz., binary aluminum-boron (Al-B) and aluminum-titanium (Al-Ti) systems, ternary aluminum-titanium-boron (Al-Ti-B) and aluminum-titanium-carbon (Al-Ti-C) systems, as well as taking into consideration the silicon-titanium-aluminide (Si-TiAl3) interaction in Al-based alloys containing Si. The analysis is supported by recent metallographic evidence obtained by the authors on A356.2 alloys. The sections on thermodynamic aspects cover the different models proposed concerning nucleation and growth on a newly formed Al grain. The value of the recalescence parameter reduces gradually with the increase in the Ti added. At a level of 0.20 wt%, this parameter becomes zero. If the concentration of grain refiner exceeds a certain amount, the grain size becomes minimal. Another parameter to be considered is the interaction between the grain refiner and traces of other metals in the base alloy. For example, Al-4%B can react with traces of Ti that may exist in the base alloy, leading to the reaction between boron and titanium to form titanium diboride (TiB2). Grain refinement is achieved primarily with TiB2 rather than aluminum diboride (AlB2), or both, depending on the Ti content in the given alloy.

A Review on Porosity Formation in Aluminum-Based Alloys.

The main objective of this review is to analyze the equations proposed for expressing the effect of various parameters on porosity formation in aluminum-based alloys. These parameters include alloying elements, solidification rate, grain refining, modification, hydrogen content, as well as the applied pressure on porosity formation in such alloys. They are used to establish as precisely as possible a statistical model to describe the resulting porosity characteristics such as the percentage porosity and pore characteristics, as controlled by the chemical composition of the alloy, modification, grain refining, and the casting conditions. The measured parameters of percentage porosity, maximum pore area, average pore area, maximum pore length, and average pore length, which were obtained from statistical analysis, are discussed, and they are supported using optical micrographs, electron microscopic images of fractured tensile bars, as well as radiography. In addition, an analysis of the statistical data is presented. It should be noted that all alloys described were well degassed and filtered prior to casting.

Serum YKL-40 in psoriasis with and without arthritis; correlation with disease activity and high-resolution power Doppler ultrasonographic joint findings.

BACKGROUND: YKL-40 may be involved in angiogenesis in psoriasis and psoriatic arthritis (PsA). High-resolution power Doppler ultrasound (PDUS) can detect angiogenesis of synovium in PsA. AIM: To assess serum YKL-40 in psoriasis patients with or without PsA, and to correlate its levels with disease activity and high-resolution PDUS findings. METHODS: In this case-control study, 48 patients with psoriasis (26 of them also had PsA) and 30 controls were assessed by high-resolution PDUS, and assayed for serum levels of YKL-40 by ELISA. Patients were clinically assessed using Composite Psoriatic Disease Activity Index (CPDAI). Total joint score (TJS) was used to assess joint involvement in PsA. RESULTS: A statistically significant elevation was found in YKL-40 levels in psoriatics with or without PsA compared with controls (P < 0.001), as well as in PsA (group II) compared to patients without arthritis (group I) (P = 0.002). CPDAI, synovial thickness score and colour Doppler ultrasound (CDUS) score were highly significantly higher in group II vs. group I (P < 0.001). In all patients, CPDAI, synovial thickness and CDUS score were positively correlated to each other, and each of them was positively correlated to serum YKL-40 levels (P < 0.05). In either group I or II, serum YKL-40 levels correlated positively with CPDAI (P < 0.05). In group II, TJS, synovial thickness and CDUS score were positively correlated to each other (P < 0.05). CONCLUSIONS: Serum YKL-40 can be used as a new biological marker for angiogenesis and disease activity in psoriasis with or without PsA. High-resolution PDUS is a non-invasive tool for the evaluation of angiogenesis in PsA patients as well as for the detection of early synovial changes in psoriasis patients without arthritis.

Telomerase activity, and tissue polypeptide specific antigen (TPS) in Egyptian breast cancer patients.

OBJECTIVES: Breast cancer is the most common malignancy among Egyptian women. The aim of this study is to evaluate the role of both telomerase and TPS estimation in assessment of breast cancer. METHODS: The study included 40 patients with breast cancer, and 20 patients with benign breast diseases. Telomerase activity in breast tissues was assessed using TRAP assay. TPS was measured in sera of the patients by ELISA. RESULTS: Telomerase positivity was 15% in benign group vs. 60% in malignant group (p = 0.0009). It was significantly correlated to stage, and lymph node status (p < 0.02). Telomerase positivity showed significant correlation to tumor recurrence (p = 0.0076) in a follow-up period of 36 months. Mean rank of TPS was significantly higher in malignant than benign groups (p < 0.001), and in telomerase positive than telomerase negative patients (p < 0.001). In malignant group, mean rank of TPS was significantly higher in late stages (p < 0.002), in higher grade (p < 0.05), in larger tumor size (p < 0.01), and in lymph node positive patients (p < 0.001). ROC curve was utilized to choose the best cutoff for serum TPS (88 U/L). At this cutoff, the sensitivity was 95%, and the specificity was 75%. At a higher cutoff (109 U/L), TPS positivity was significantly correlated to stage, grade, lymph node status, and telomerase positivity (p < 0.05). CONCLUSION: Telomerase positivity and serum TPS might be used as additional markers for assessment of breast cancer.