Mekanik Alaşımlama Yöntemi ile Üretilen AA7075 Al Alaşımlarının Mikroyapısal ve Mekanik Özellikleri

Öz

Bu çalışmada, mekanik alaşımlama ve sinterleme yöntemleri ile AA7075 malzemelerinin üretilmesi amaçlanmıştır. Ayrıca, bu çalışmanın temel amacı, farklı bilyeli öğütme sürelerinin toz ve sinterlenmiş numuneler üzerindeki etkisini araştırmaktır. Öğütülmüş tozlar ve sinterlenmiş numuneler, farklı karakterizasyon teknikleri ile kapsamlı bir şekilde incelenmiştir. Başlangıçta, hazır olarak temin edilen AA7075 alaşım tozu, farklı öğütme sürelerinde gezegensel yüksek enerjili bilyeli öğütme cihazı ile öğütülmüştür. Ticari kalite AA7075 tozların başlangıç partikül boyutu 46 µm olarak hesaplanırken, 8 saatlik öğütülmüş tozların ortalama partikül boyutu 22 µm olarak ölçülmüştür. Öğütülmüş AA7075 alaşım tozların morfolojik özellikleri üzerindeki farklı öğütme sürelerinin (yani 0,5, 1, 2, 4 ve 8 saat) etkisi, taramalı elektron mikroskobu (SEM) analizi ve partikül boyut analizleri ile araştırılmıştır. Ek olarak, öğütülmüş tozların kristalografik özelliklerindeki farklılıkları gözlemlemek için X-ışını toz kırınımı (XRD) yapılmıştır. Toz hazırlama ve karakterizasyon aşamalarından sonra, üretilen AA7075 numunelerinin mekanik özelliklerine öğütme işleminin farklı aşamalarının etkisini belirlemek amacıyla, öğütülen bu tozlar soğuk pres ve ardından sinterleme işlemi ile konsolide edilmiştir. Deneysel sonuçlara göre, öğütme süresi son aşamaya (8 saat) ulaştığında, sinterlenmiş AA7075'in bağıl yoğunluğunun %7 azaldığı, buna karşın aynı üretim geçmişi ile üretilen saf AA7075 numunesine göre sertliğin %130 arttığı gözlemlenmiştir.

Anahtar Kelimeler

• AA7075
• Bilyeli Öğütme
• Mikroyapı
• Mekanik Özellikler

Microstructural and Mechanical Properties of AA7075 Al Alloys Produced via Mechanical Alloying Process

Abstract

In this study, it is aimed to produce AA7075 materials by mechanical alloying and sintering methods. Besides, the main purpose of this study is to investigate the effect of different ball milling times on the powder and sintered samples. The milled powders and sintered samples were thoroughly investigated by different characterization techniques. Initially, AA7075 alloy powders were milled by planetary high-energy ball milling device with different milling times. While the initial particle size of commercial grade AA7075 powders were calculated 46 µm, the average particle size of the 8 hours milled powders measured as 22 μm. The effect of different milling times (i.e., 0.5, 1, 2, 4 and 8 hours) on the morphological properties of AA7075 milled powders were investigated by scanning electron microscopy (SEM) and particle size analyses. In addition, X-ray powder diffractometry (XRD) was performed to observe the differences in the crystallographic properties of the milled powders. After the powder preparation and characterization stages, in order to determine the effect of the different phases of milling process on the mechanical properties of the produced AA 7075 samples, these milled powders were consolidated via cold press followed by sintering process. According to experimental outcomes, it was observed that when the milling time reached the final stage (8 hours), the relative density of bulk AA7075 decreased by 7%, in contrast the hardness increased by 130% as compared to pure AA7075 sample fabricated by same producing history.

Keywords

• AA7075
• Ball Milling
• Microstructure
• Mechanical Properties

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