Investigation of wear behavior of aged and non-aged SiC-reinforced AlSi7Mg2 metal matrix composites in dry sliding conditions

Metal matrix composites (MMCs) with their splendid mechanical properties have been specifically designed for use in fields such as aerospace and aviation. The presence of hard ceramic particles in MMC increases the hardness of the matrix product and decreases its coefficient of friction. Therefore, the wear resistance is improved. Moreover, the mechanical properties of these composite materials can be improved by applying heat treatments. In this study, AlSi7Mg2 MMCs with 15 wt% SiC reinforcement were produced by squeeze casting technique. Some of the composites were aged by heat treatment. Hardness values of aged and non- aged composites were compared. In addition, abrasive wear behaviors of these composites were investigated on pin-on-disk device, depending on the load (7, 12 and 17 N), the sliding speed (0.2, 0.3 and 0.4 m/s) and the sliding distance (700, 1000 and 1300 m). Worn surfaces were also analyzed by scanning electron microscopy (SEM). As a result of the analyses, it was determined that both the hardness values and the wear resistance were higher in the composites subjected to aging treatment. Furthermore, it was observed that the increase in the applied load led up to the weight loss. The increase in the sliding distance increased both friction coefficient and weight loss. The increase in sliding speed also made way for the friction coefficient but ensured less weight loss. When SEM images were examined, it was ascertained that deformation and tribo-surface formation had a significant effect on weight losses

Razine pentraksina 3 dobro su povezane s težinom bolesti kod prijma u bolesnika s COVID-19

Pentraxin 3 (PTX3), a long pentraxin, is not only released from dendritic cells and neutrophils but also from epithelial and endothelial cells such as alveolar epithelium. Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) initially activates the innate immune system, causing a complex immune response. Clinical and experimental studies suggest that PTX3, a locally and systemically secreted marker, can be used as a predictor of the severity and mortality in respiratory infections. In the current study, serum PTX3 levels in patients hospitalized with COVID-19 were found to be significantly increased at admission and showed significant association with the disease severity.Pentraksin 3 (PTX3), dugi pentraksin, ne oslobađa se samo iz dendritičnih stanica i neutrofila, nego i iz epitelnih i endotelnih stanica poput alveolarnog epitela. Teški akutni respiracijski sindrom koronavirus-2 (SARS-CoV-2) u početku aktivira urođeni imuni sustav uzrokujući složen imuni odgovor. Klinička i eksperimentalna istraživanja ukazuju na to da se PTX3, lokalno i sistemski izlučeni biljeg, može koristiti kao prediktor težine i smrtnosti kod respiracijskih infekcija. U ovom istraživanju utvrđeno je da su razine PTX3 u serumu bolesnika hospitaliziranih s COVID-19 bile značajno povišene kod prijma i značajno povezane s težinom bolesti

ALUMİNYUM ALAŞIMLARININ SIKIŞTIRILMASI DÖKÜMLE T6 ISIL İŞLEMİ

ALUMİNYUM ALAŞIMLARININ SIKIŞTIRILMASI DÖKÜMLE T6 ISIL İŞLEM

Yarı Katı Döküm Tekniği İle Yüksek Dayançlı Aluminyum Alaşımlarının Geliştirilmesi.

Bu projede yüksek performanslı aluminyum alaşım otomotiv ve savunma sanayi parçaları geliştirmek için yarı katı döküm yöntemi kullanılacaktır. Hazırlanacak aluminyum alaşımları yarıkatı sıcaklık aralığında mevcut bir dik hidrolik pres kullanılarak basınç altında son şekillendirilecektir. Elde edilecek alaımlar daha son sonra mekanik testler yapılarak karakterize edilecektir

FEN BİLİMLERİ ENSTİTÜSÜ/LİSANSÜSTÜ TEZ PROJESİ

6000 SERİ ALÜMİNYUM ALAŞIMLI PLAKLARIN ARABA GÖVDELERİ İÇİN SUPERPLASTİK YÖNTEM İLE ŞEKİLLENDİRİLMES

THERMAL CONDUCTİVİTY OF COMPACTED GRAPHİTE IRON

THERMAL CONDUCTİVİTY OF COMPACTED GRAPHİTE IRO

FEN BİLİMLERİ ENSTİTÜSÜ/LİSANSÜSTÜ TEZ PROJESİ

HELİHOPTER DİŞLİ KUTULARI İÇİN MAGNEZYUM ALAŞIMLARI GELİŞTİRİLMES

Effect of cooling rate on microstructure and high temperature stability of rapidly solidified Al-Fe-V-Si alloys

Recently, AI-Fe-V-Si alloys have received more attention owing to their high temperature stability associated with vanadium rich precipitates and silicides. In this work, a series of alloys was prepared and processed by melt spinning and gas atomisation to observe the effect of solidification rate on crystal structures existing in both as cast and heat treated conditions. This study covers their microstructural examination and crystallography. The composition of these alloys was Al-(6.8-7.8)Fe-( 1.0-3)V-(1.6-2.2)Si and the ribbons and powders produced were examined by SEM and TEM. Investigations revealed that most of the rapidly solidified ribbons and powders consisted of a cellular structure with cubic spherical dispersoids and quasicrystalline i phase spheroids. The proportions of these phases were found to be dependent on section thickness and cooling rate of the products. More i phase spheroids were observed in sections of melt spun ribbons and coarse powders. After heat treatment at 300, 400, and 500 degrees C, the sizes of these dispersoids were detected to be two or three times the original as cast sizes. PM/0803 (C) 1999 IoM Communications Ltd