Effect of Ambient and Cryogenic Milling on the Microstructure and Properties of Tungsten Matrix Composites Fabricated by Activated Sintering

Özge Balcı; Duygu Ağaoğulları; Mehmet Suat Somer; M. Lütfi Öveçoğlu

doi:10.17776/csj.385724

EN TR

Effect of Ambient and Cryogenic Milling on the Microstructure and Properties of Tungsten Matrix Composites Fabricated by Activated Sintering

Abstract

Tungsten matrix composites reinforced with TiB₂ and Y₂O₃ particles were fabricated by milling under ambient/cryogenic conditions and Ni activated sintering. Powder blends constituting the W - 1 wt. % Ni - 2 wt. % TiB₂ - 1 wt. % Y₂O₃ composition were mechanically milled for 12 h under ambient condition or cryomilled for 10 min or sequentially milled under ambient and cryogenic conditions. Milling was carried out in a high-energy ball mill under ambient condition whereas cryogenic milling was conducted in externally circulated liquid nitrogen. Milled powders were compacted using a hydraulic press and the pellets were sintered at 1400°C for 1 h under Ar / H₂ gas flowing conditions. The effects of different milling types on the microstructural and mechanical properties of the sintered composites were investigated. After sintering, in addition to dominant W phase, small amounts of WB and NiW phases were detected in all sintered samples. The application of cryomilling after milling at ambient condition provided the disappearance of the clustered TiB₂ and Y₂O₃ particles in the sintered sample: They were located at the grain boundaries of W1Ni matrix and homogeneously distributed through the microstructure. Sequentially milled and sintered composite had the highest relative density (95.77 %) and the highest microhardness (7.23 GPa) values among the samples. Nano-indentation tests showed that there was an improvement in the hardness and elastic modulus of W matrix phase, which yielded the values of 8.9 and 373.7 GPa, respectively.

Keywords

Tungsten matrix composites,Cryomilling,Activated sintering,TiB2,Y2O3

Normal ve Kriyojenik Şartlarda Öğütmenin Aktive Edilmiş Sinterleme Süreçleri ile Geliştirilen Tungsten Esaslı Kompozitlerin Mikroyapı ve Özellikleri Üzerindeki Etkisi

Öz

Bu çalışmada, Ni ile aktive edilerek sinterlenen tungsten esaslı matrisin TiB₂ ve Y₂O₃ partikülleri ile takviye edilmesiyle, tungsten esaslı kompozit malzeme üretimi gerçekleştirilmiştir. W - % 1 ağ. Ni - % 2 ağ. TiB₂ - % 1 ağ. Y₂O₃ kompozisyonundan oluşan toz harmanları, normal koşullarda 12 sa mekanik olarak öğütülerek ya da 10 dk kriyojenik ortamda öğütülerek ya da normal ve kriyojenik şartlarda ardışık olarak öğütülerek hazırlanmıştır. Normal şartlarda öğütme yüksek enerjili bir değirmende uygulanırken; kriyojenik şartlarda öğütme sıvı azot ile dışarıdan çevrelenen bir sistemde yapılmıştır. Öğütülmüş tozlar hidrolik pres kullanılarak preslenmiş ve pekiştirilen bünyeler Ar/H₂ gazaltı şartlarında 1400°C’de 1 sa sinterlenmiştir. Farklı öğütme koşullarının sinterlenen kompozit malzemelerin mikroyapısı ve özellikleri üzerindeki etkisi incelenmiştir. Sinterlenme sonrasında, baskın W fazına ek olarak düşük mikarda WB ve NiW fazları oluşumu gözlemlenmiştir. Normal şartlarda öğütme sonrası uygulanan kriyojenik öğütme, sinter malzemelerin mikroyapısındaki TiB₂ ve Y₂O₃ partiküllerin topaklanmasının yok olmasına neden olmuştur: Partiküllerin W1Ni matrisinin tane sınırlarında ve homojen olarak mikroyapıda dağılması sağlanmıştır. Ardışık olarak öğütülmüş ve sinterlenmiş kompozitler, numuneler arasında en yüksek rölatif yoğunluk (% 95,77) ve mikrosertlik değerlerini (7,23 GPa) sunmuştur. Nano-indentasyon testleri sayesinde, W matris fazının sertlik ve elastisite modül değerlerinin sırasıyla 8,9 ve 373,7 GPa değerlerine kadar iyileştirildiği kanıtlanmıştır.

Anahtar Kelimeler

Tungsten esaslı kompozitler,kriyojenik öğütme,aktive edilmiş sinterleme,TiB2,Y2O3

References

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Details

Primary Language

English

Subjects

-

Journal Section

Research Article

Authors

Özge Balcı ^*
KOÇ ÜNİVERSİTESİ
0000-0001-6756-3180
Türkiye

Duygu Ağaoğulları
İSTANBUL TEKNİK ÜNİVERSİTESİ
0000-0002-0623-5586
Türkiye

Mehmet Suat Somer
KOÇ ÜNİVERSİTESİ
0000-0001-5606-9101
Türkiye

M. Lütfi Öveçoğlu
İSTANBUL TEKNİK ÜNİVERSİTESİ
0000-0002-1536-4961
Türkiye

Publication Date

March 22, 2019

Submission Date

January 29, 2018

Acceptance Date

December 25, 2018

Published in Issue

Year 1970 Volume: 40 Number: 1

DOI

https://doi.org/10.17776/csj.385724

IZ

https://izlik.org/JA82NE63XD

Cite

RIS / Bibtex

APA

Balcı, Ö., Ağaoğulları, D., Somer, M. S., & Öveçoğlu, M. L. (2019). Effect of Ambient and Cryogenic Milling on the Microstructure and Properties of Tungsten Matrix Composites Fabricated by Activated Sintering. Cumhuriyet Science Journal, 40(1), 204-212. https://doi.org/10.17776/csj.385724

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