Bilyalı Dövme Parametrelerinin AA7075 T6 Alüminyum Alaşımının Yüzey Altı Özelliklerine Etkileri

Bilyalı dövme işlemi özellikle otomotiv ve havacılık endüstrilerinde değişken yüklemeler altındaçalışan makine elemanlarının yorulma ömürlerinin geliştirilmesi için yaygın olarak uygulananönemli bir mekanik yüzey işleme yöntemidir. Yorulma ömrünün geliştirilmesi; bilyalı dövme ilemalzeme yüzey altı mikroyapısı ve mekanik özelliklerinin iyileştirilerek çatlak oluşumununengellenmesi ve oluşan çatlakların ilerleme hızlarının yavaşlatılması ile sağlanmaktadır. Buçalışmada farklı bilyalı dövme parametreleri altında dövülen AA7075 T6 alüminyum alaşımınınyüzey altı mikroyapısında ve mekanik özelliklerinde meydana gelen değişimlerin incelenmesiamaçlanmıştır. Bilya boyutu ve bilya püskürtme basıncı parametrelerinin yüzey altı sertlikdeğerlerine ve yüzey altı mikroyapısına etkileri derinliğe bağlı olarak incelenmiştir. Bilyalıdövme deneyleri özel olarak tasarlanan bilyalı dövme test sisteminde 0,1-0,3 mm ve 0,4-0,9 mmçaplarında paslanmaz çelik bilyalar ile 2 ve 4 bar püskürtme basınçları altında gerçekleştirilmiştir.Püskürtme basıncı ve bilya boyutunun artışı ile yüzey altı sertlik değerleri belirgin bir şekildeiyileşmiş ve sertlik artışı gözlenen bölgenin derinliği artmıştır. Püskürtme basıncının artışı ile heriki bilya boyutunda da mikroyapısal değişime uğrayan bölgenin derinliği artış göstermiştir.Püskürtme basıncı ve bilya boyutu artışı nedeniyle meydana gelen aşırı plastik deformasyonnedeniyle yüzeyde derin ve geniş çukurcukların ve yüzeysel mikro çatlakların oluşumubelirlenmiştir.

The Effects of Shot Peening parameters on the subsurface properties of AA7075 T6 aluminum alloy

Shot peening (SP) is an important mechanical surface treatment widely used to improve the fatigue life of mechanical components operating under dynamic loads which have been specifically used in automotive and aerospace industries. The enhancement of the fatigue life is achieved by preventing the crack formation and slowing crack propagation by improving the mechanical properties and the microstructure of subsurface via SP. In this study, it is aimed to investigate the variation of the subsurface microstructure and the subsurface mechanical properties of AA7075 T6 aluminum alloy shot-peened under different parameters. The subsurface hardness and microstructural variations were investigated in relation to depth depending on the shot size and the peening pressure. SP was conducted under specially designed SP system by stainless steel shots of 0.1-0.3 mm and 0.4-0.9 mm diameters under 2 and 4 bar peening pressures. Subsurface hardness values improved significantly by increasing pressure and shot size, and the depth of the hardness increased regions was increased. The depth of the microstructural region affected by SP also increased for both shot sizes. The formation of deep and large pits and surface microcracks were determined on the surface due to the excessive plastic deformation that occurs with increases in pressure and shot size.

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