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On the governing fragmentation mechanism of primary intermetallics by induced cavitation.

ABSTRACT: One of the main applications of ultrasonic melt treatment is the grain refinement of aluminium alloys. Among several suggested mechanisms, the fragmentation of primary intermetallics by acoustic cavitation is regarded as very efficient. However, the physical process causing this fragmentation has received little attention and is not yet well understood. In this study, we evaluate the mechanical properties of primary Al₃Zr intermetallics by nano-indentation experiments and correlate those with in-situ high-speed imaging (of up to 1 Mfps) of their fragmentation process by laser-induced cavitation (single bubble) and by acoustic cavitation (cloud of bubbles) in water. Intermetallic crystals were chemically extracted from an Al-3 wt% Zr alloy matrix. Mechanical properties such as hardness, elastic modulus and fracture toughness of the extracted intermetallics were determined using a geometrically fixed Berkovich nano-diamond and cube corner indenter, under ambient temperature conditions. The studied crystals were then exposed to the two cavitation conditions mentioned. Results demonstrated for the first time that the governing fragmentation mechanism of the studied intermetallics was due to the emitted shock waves from the collapsing bubbles. The fragmentation caused by a single bubble collapse was found to be almost instantaneous. On the other hand, sono-fragmentation studies revealed that the intermetallic crystal initially underwent low cycle fatigue loading, followed by catastrophic brittle failure due to propagating shock waves. The observed fragmentation mechanism was supported by fracture mechanics and pressure measurements using a calibrated fibre optic hydrophone. Results showed that the acoustic pressures produced from shock wave emissions in the case of a single bubble collapse, and responsible for instantaneous fragmentation of the intermetallics, were in the range of 20-40 MPa. Whereas, the shock pressure generated from the acoustic cavitation cloud collapses surged up to 1.6 MPa inducing fatigue stresses within the crystal leading to eventual fragmentation.

SUBMITTER: Priyadarshi A

PROVIDER: S-EPMC7786528 | biostudies-literature | 2021 Jan

REPOSITORIES: biostudies-literature

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On the governing fragmentation mechanism of primary intermetallics by induced cavitation.

Priyadarshi Abhinav A Khavari Mohammad M Subroto Tungky T Conte Marcello M Prentice Paul P Pericleous Koulis K Eskin Dmitry D Durodola John J Tzanakis Iakovos I

Ultrasonics sonochemistry 20200724

One of the main applications of ultrasonic melt treatment is the grain refinement of aluminium alloys. Among several suggested mechanisms, the fragmentation of primary intermetallics by acoustic cavitation is regarded as very efficient. However, the physical process causing this fragmentation has received little attention and is not yet well understood. In this study, we evaluate the mechanical properties of primary Al<sub>3</sub>Zr intermetallics by nano-indentation experiments and correlate th ...[more]

PMID: 32818723

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Project description:BackgroundAntiangiogenic agent-treated patients usually develop cavitation in their lung lesions. The clinical significance of lung cavitation development during antiangiogenic therapy has not been determined yet. Herein, we evaluated the clinical outcomes of patients who developed tumor cavitation following apatinib treatment and explored the mechanisms.MethodsIn this study (Clinical Trial No. NCT03629691), 187 patients (77 lung cancer and 110 gastric adenocarcinoma patients) who had progressed or relapsed after undergoing at least two lines of systemic therapy in accordance with the NCCN guidelines for primary or metastatic lung tumors were treated with apatinib at a dosage of 250 mg per day between February 1, 2015 and May 19, 2017. The effect of lung cavitation development on locoregional control (LRC), progression-free survival (PFS), and overall survival (OS) was analyzed with Kaplan-Meier estimates and compared with the log-rank test. Zebrafish experiments were used to study the anticancer mechanism of apatinib in different tumors. Western-blotting was used to analyze the expression of Cyclin D1, p53, HIF-α, and VEGFR before and after apatinib treatment in both normoxia and hypoxia.ResultsCavitation development was beneficial in patients receiving apatinib therapy regardless of whether they had primary or metastatic lung cancer. Zebrafish experiments showed that apatinib inhibited tumor growth by both suppressing vascular growth and inhibiting cell proliferation. Vascular proliferation induced by the H1299 cell lines showed higher sensitivity to apatinib than that induced by the SCG-7901 cell line. However, apatinib showed weak tumor type selectivity on cell proliferation inhibition in vivo. Under hypoxic conditions, apatinib could not inhibit the protein expression of VEGFR and HIF-α in both cell lines; however, apatinib decreased the expression of cyclin D1 and P53 significantly.ConclusionsLung cavitation development is common with apatinib therapy and is a potential prognostic marker. Apatinib inhibits tumor growth by both vessel growth inhibition and proliferation inhibition.

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On the governing fragmentation mechanism of primary intermetallics by induced cavitation.

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On the governing fragmentation mechanism of primary intermetallics by induced cavitation.

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