Saffil $(delta-Al_2 O_3)$ fiber takviyeli ZA-12 alaşımım sürtünme aşınma davranışları

Bu çalışmada %10, %20 ve %30 hacim oranında alümina saffil ( δ-Al2O3) fiber içeren çinko–alüminyum esaslı alaşımın (ZA-12) sürtünme aşınma davranışları incelenmiştir. Numuneler saffil fiber preformlara vakum altında “sıvı metal infiltrasyon” yöntemiyle üretilen kompozit levhalardan hazırlanmıştır. Seramik fiberler yaklaşık 3 mikron çapında ve ortalama 500 mikron boyunda olup kompozit levhada düzlem içinde gelişigüzel (planar random) dağılmış haldedir. Sürtünme-aşınma deneyleri pim/disk tipi bir test makinesinde 20, 25 ve 30 N yükler altında yapılmıştır. Fiberlerin disk yüzeyine dik olmasına özen gösterilmiştir. Ağırlık kaybı (aşınma kaybı) ve sürtünme katsayısı belirlenmiş ve bunların fiber hacım oranı ile ilişkileri gösterilmiştir. Ağırlık kaybının yük ve fiber oranı ile arttığı, sürtünme katsayısının ise alaşımınkine göre daha büyük olduğu görülmüştür. Aşınma davranışlarını belirlemek için numunelerin hem aşınma yüzeyleri hem de bu yüzeye dik kesitleri elektron mikroskopta (SEM) incelenerek karşılaştırılmıştır. Buna göre fiberlerin plastik deformasyonu azalttığı, sürtünme direncini ise artırdığı fakat kopan fiber parçacıkların matrise gömülerek sürüklenmesi nedeniyle daha fazla aşınmaya sebep olduğu görülmüştür.

Wear behaviour of ZA-12 alloy composites reinforced with saffil $(delta-Al_2 O_3)$ fibres

In this study the wear behaviour of a zinc-aluminum base alloy (ZA-12) containing 10, 20 and 30 % δ-Al2O3 (alumina saffil) has been investigated. Specimens were produced from disc-shaped composite plates made from saffil fibre preforms vacuum infiltrated with molten alloy. The ceramic fibres with about 3 μm in diameter and an average length of 500 μm have a planar random distribution in the composite plates. The wear tests were carried out using the pin-on-disc type wear test apparatus under loads of 20, 25 and 30 N. The tests were performed on samples in which the fibres are perpendicular to the wear surface. The wear rate and the coefficient of friction of the composites were determined and plotted over a range of loads and volume fractions of fibers. In general the wear rate increased with an increase in volume fraction of fibre and load. The coefficients of friction of composites were higher than that of the unreinforced matrix alloy. The surfaces and sections perpendicular to the worn surfaces of the pins were examined by scanning electron microscopy (SEM) to determine the causes of the behaviour. Comparison of images allowed a correlation between wear rates and structures of the worn surface and subsurface layers developed during wear testing. It was found that the presence of fibres reduced the amount of subsurface plastic deformation, but the increase in wear rate compared with the unreinforced matrix alloy was principally due to the abrasive wear caused by the fragments of short delta-alumina (saffil) fibers embedded in the matrix alloy.

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