MEKANOKİMYASAL YÖNTEMLE ÜRETİLEN ALÜMİNYUM MATRİSLİ KOMPOZİT MALZEMELERİN YÜKSEK SICAKLIKLARDAKİ TRİBOLOJİK DAVRANIŞLARININ ARAŞTIRILMASI
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2021-07
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info:eu-repo/semantics/openAccess
Özet
Bu çalışmada, mekanokimyasal reaksiyon yöntemi ile A356-Grafit (Gr)-Zirkonyum oksit (ZrO2) ve A356-Grafit (Gr)-Titanyum karbür (TiC) takviyeli alüminyum matrisli kompozitlerin (AMK) üretimi, karakterizasyonu ve yüksek sıcaklıklarda aşınma davranışları incelenmiştir. Çalışma iki aşamada gerçekleştirilmiştir. Çalışmanın ilk aşamasında, A356 alaşımı matrise, katı yağlayıcı olarak %2 grafit ve takviye malzemesi olarak dört farklı miktarda (%3, %6, %9 ve %12) ZrO2 ilave edilerek kompozit tozlar hazırlanmıştır. Çalışmanın ikinci aşamasında takviye olarak TiC kullanılmıştır. Mekanokimyasal reaksiyon yöntemi, planeter tip değirmende bilyalı öğütme işlemi ile yapılmıştır. Bilyalı öğütme ile mekanokimyasal reaksiyon işlemi uygulanan kompozit tozlar ön şekillendirilmiş ve vakum ortamında (10-6 mbar) sinterlenmiştir. Üretilen AMK’ler mikro yapı incelemeleri, sertlik ve yoğunluk ölçümleri ile karakterize edilmiştir. Aşınma testleri standart pin-on-disk tipi aşınma test cihazında sıcaklık modülü ilave edilerek yapılmıştır. Aşınma testlerinde üç farklı yük (10-20-30 N) üç farklı kayma mesafesi (53-72-94 m) ve beş farklı sıcaklık (20-100-180-260-340 °C) ve 0,5 ms-1 kayma hızı kullanılmıştır. Aşınma testlerinde kullanılan kayma mesafesi belirli hızlarda seyreden bir aracın güvenli durma mesafesi olarak alınmıştır. Yapılan çalışmalar sonucunda, bilyalı öğütme ve mekanokimyasal reaksiyon işlemi ile her iki takviye malzemesi de matris tozları içerisine gömülmüş ve kompozit bir yapı elde edilmiştir. Bilyalı öğütme ile mekanokimyasal reaksiyon işleminde her iki takviye malzemesi de (ZrO2, TiC) nano boyuta kadar küçüldüğü ve özellikle tane sınırlarında konumlandığı görülmüştür. Yoğunluk sonuçlarında, üretilen her iki takviyeli AMK’lerde artan takviye miktarıyla yoğunlukların arttığı, bağıl yoğunluklarında ise azaldığı belirlenmiştir. En yüksek bağıl yoğunluk matris malzemesinde elde edilirken, en yüksek yoğunluk %12 takviye ilave edilen kompozit malzemelerde elde edilmiştir. Benzer şekilde sertlik sonuçlarında takviye miktarının artmasıyla sertlikler artmıştır. Her iki takviye malzemesinde de en yüksek sertlik %12 ilave edilen (ZrO2 ilavesiyle 680 HV, TiC ilavesiyle 825 HV) kompozit malzemelerde elde edilmiştir. Aşınma testleri sonucunda üretilen kompozit malzemelerin ağırlık kaybı, artan yük, kayma mesafesi ve çalışma sıcaklığının artmasıyla artmaktadır. Her iki takviye malzemesinde en düşük ağırlık kaybı bütün yük ve sıcaklıklarda %12 takviye ilave edilen kompozit malzemede elde edilmiştir. Aşınma oranı sonuçlarında belirli bir düzenin olmadığı genel olarak 20 N yük altında her iki takviye malzemesinde de en düşük aşınma oranı elde edilmiştir. Artan çalışma sıcaklıklarıyla aşınma oranları da artmaktadır. Sürtünme katsayıları sonuçlarında ise bütün çalışma sıcaklıklarında ani artışların olduğu görülmüştür. Ancak genel olarak artan kayma mesafesiyle sürtünme katsayıları azalırken yük ve sıcaklıklığın artmasyıla sürtünme katsayıları azalmaktadır. Aşınma testi sonuçlarında her iki takviye malzemesinde de 180 °C sıcaklıktan sonra şiddetli aşınmanın olduğu görülmüştür.
In this study, the production, characterization and wear behavior at high temperatures of A356-Graphite (Gr)-Zirconium oxide (ZrO2) and A356-Graphite -Titanium carbide (TiC) reinforced aluminum matrix composites (AMC) were investigated by mechanochemical reaction method. The study was performed in two stages. In the first stage of the study, composite powders were prepared by adding 2% graphite as a solid lubricant and ZrO2 in four different amounts (3%, 6%, 9% and 12%) as reinforcement material to the A356 alloy matrix. In the second stage of the study, TiC was used as reinforcement. The mechanochemical reaction method was made by ball milling in a planetary type mill. Composite powders, which are applied mechanochemical reaction process by ball milling, are preformed and sintered in vacuum environment (10-6 mbar). The produced AMCs were characterized by microstructure studies, hardness and density measurements. Wear tests were carried out in a standard pin-on-disc type wear tester by adding a temperature module. In abrasion tests, three different loads (10-20-30 N), three different sliding distances (53-72-94 m) and five different temperatures (20-100-180-260-340 °C) and 0.5 ms-1 sliding speed has been used. The sliding distance used in the wear tests was taken as the safe stopping distance of a vehicle traveling at certain speeds. As a result of the studies, both reinforcement materials were embedded in matrix powders by ball milling and mechanochemical reaction processes and a composite structure was obtained. In the mechanical reaction process with ball milling, it has been observed that both reinforcement materials (ZrO2, TiC) shrink to nano size and are located especially at the grain boundaries. In the density results, it was determined that in both reinforced AMCs produced, the densities increased with the increasing amount of reinforcement and their relative densities decreased. While the highest relative density was obtained in the matrix material, the highest density was obtained in composite materials with 12% reinforcement. Similarly, the hardness increased with the increase in the amount of reinforcement in the hardness results. In both reinforcement materials, the highest hardness was obtained in composite materials with 12% added (680 HV with ZrO2 addition, 825 HV with TiC addition). As a result of the wear test the weight loss of produced composites increased with increasing load, sliding distance and increasing operating temperature. In both reinforcement materials, the lowest weight loss was achieved in the composite material with 12% reinforcement at all loads and temperatures. In general, there is no particular pattern in the wear rate results, and the lowest wear rate was obtained in both reinforcement materials under 20 N load. With increasing operating temperatures, the wear rate is also increasing. In the friction coefficient results, it was seen that there were sudden increases in all operating temperatures. However, in general, the friction coefficients decreased with increasing sliding distance, while friction coefficients decreased with increasing load and temperature. In the wear test results, it was seen that both reinforcement materials had severe abrasion after 180 °C."
In this study, the production, characterization and wear behavior at high temperatures of A356-Graphite (Gr)-Zirconium oxide (ZrO2) and A356-Graphite -Titanium carbide (TiC) reinforced aluminum matrix composites (AMC) were investigated by mechanochemical reaction method. The study was performed in two stages. In the first stage of the study, composite powders were prepared by adding 2% graphite as a solid lubricant and ZrO2 in four different amounts (3%, 6%, 9% and 12%) as reinforcement material to the A356 alloy matrix. In the second stage of the study, TiC was used as reinforcement. The mechanochemical reaction method was made by ball milling in a planetary type mill. Composite powders, which are applied mechanochemical reaction process by ball milling, are preformed and sintered in vacuum environment (10-6 mbar). The produced AMCs were characterized by microstructure studies, hardness and density measurements. Wear tests were carried out in a standard pin-on-disc type wear tester by adding a temperature module. In abrasion tests, three different loads (10-20-30 N), three different sliding distances (53-72-94 m) and five different temperatures (20-100-180-260-340 °C) and 0.5 ms-1 sliding speed has been used. The sliding distance used in the wear tests was taken as the safe stopping distance of a vehicle traveling at certain speeds. As a result of the studies, both reinforcement materials were embedded in matrix powders by ball milling and mechanochemical reaction processes and a composite structure was obtained. In the mechanical reaction process with ball milling, it has been observed that both reinforcement materials (ZrO2, TiC) shrink to nano size and are located especially at the grain boundaries. In the density results, it was determined that in both reinforced AMCs produced, the densities increased with the increasing amount of reinforcement and their relative densities decreased. While the highest relative density was obtained in the matrix material, the highest density was obtained in composite materials with 12% reinforcement. Similarly, the hardness increased with the increase in the amount of reinforcement in the hardness results. In both reinforcement materials, the highest hardness was obtained in composite materials with 12% added (680 HV with ZrO2 addition, 825 HV with TiC addition). As a result of the wear test the weight loss of produced composites increased with increasing load, sliding distance and increasing operating temperature. In both reinforcement materials, the lowest weight loss was achieved in the composite material with 12% reinforcement at all loads and temperatures. In general, there is no particular pattern in the wear rate results, and the lowest wear rate was obtained in both reinforcement materials under 20 N load. With increasing operating temperatures, the wear rate is also increasing. In the friction coefficient results, it was seen that there were sudden increases in all operating temperatures. However, in general, the friction coefficients decreased with increasing sliding distance, while friction coefficients decreased with increasing load and temperature. In the wear test results, it was seen that both reinforcement materials had severe abrasion after 180 °C."
Açıklama
Anahtar Kelimeler
Aluminum matrix composites, wear behaviour, mechanochemical reaction, hot wear., Alüminyum matrisli kompozit, aşınma davranışı, mekanokimyasal reaksiyon, sıcak aşınma.