YAŞLANABİLİR AA 7075 KALİTE AL ALAŞIMININ AŞINMA VE KOROZYON DAVRANIŞINA BORAKS İLAVESİNİN VE HADDELEME İŞLEMİNİN ETKİSİ
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2023-08
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info:eu-repo/semantics/openAccess
Özet
Bu çalışmada Al7075 alaşımına sıvı eriyik yöntemiyle ağırlıkça %15 ve %30 oranlarında boraks (Na?[B?O?(OH)?]·8H?O) ilave edilmesinin alaşımın mekanik özelliklerine etkisi incelenmiştir. Al7075 alaşımına boraks pota içinde ilave edilerek bor alüminyum bileşikleri elde edilmiştir. Elde edilen Al7075+%15 borakslı ve Al7075+%30 borakslı kompozitleri %50 ve %80 oranlarında soğuk haddeleme işlemine tabi tutulmuştur. Ayrıca bir kısım numunelere T6 ısıl işlemi uygulanarak çökeltme sertleşmesiyle ve yaşlandırmayla T6 ısıl işleminin etkileri incelenmiştir. Elde edilen numunelerin spektral analiz, mikro yapı, brinell sertlik, kuru aşınma ve potansyodinamik korozyon davranışları incelenmiştir. Deneylerin ardından, numunelerin yüzeylerindeki faz durumlarını incelemek amacıyla EDX analizleri ve SEM görüntüleri alınmıştır. %15 borakslı, %30 borakslı ve boraks ilavesiz Al7075 numunelerden alınan mikroyapılarda yapılan ortalama tane boyutu ölçümü sonucunda boraks ilavesi arttıkça ortalama tane boyutunun boraks ilavesiz Al7075 nununesine (111 µm) göre büyüdüğü gözlemlenmiştir. Boraks ilaveli numunelere T6 ısıl işlemi uygulandığında, ortalama tane boyutunun küçüldüğü (%15 borakslı %18.8, %30 borakslı %5.5 azalır) gözlemlenmiştir. %50 ve %80 soğuk haddeleme işlemlerinden sonra T6 ısıl işlem uygulandığında, tane boyutunun Al7075 malzemesinin tane boyutundan daha küçük tane boyutu elde edildiği gözlemlenmiştir. Yapılan setlik ölçümü sonucunda en yüksek sertlik değeri %80 oranında haddelenmiş %15 borakslı numunede (84.11 BH) bulunurken, en düşük sertlik değeri %50 oranında haddelenmiş %30 borakslı numunede (65.54 BH) gözlemlenmiştir. T6 ısıl işlem uygulandığında ise en yüksek sertlik değeri %80 oranında haddelenmiş %30 borakslı numunede (74.83 BH) bulunurken en düşük sertlik değeri %30 borakslı numunede (65 BH) bulunmuştur. Aşınma sonuçlarına bakıldığında boraks ilavesi 0.0223 g toplam ağırlık kaybına sahip olan Al7075 malzemeye göre ağırlık kaybını arttırmıştır ancak boraks ilavesinin artırılmasıyla toplam ağırlık kaybında düşüş (%15 borakslı numunede 0.0336 gram iken %30 borakslı numunede 0.031 grama düşmüştür) dolayısıyla aşınma direncinde artış görülmüştür. Bu iki numuneye T6 ısıl işlem uygulandığında %30 borakslı numunenin ağırlık kaybı %7.74 oranında düşerken %15 borakslı numunede %42.56 oranında artmıştır. Haddeleme işlemi, tek başına numunelerin aşınma direncini haddelenmeden önceki durumlarına göre iyileştirmiştir. T6 ısıl işlem görmüş numunelerin verilen ağrılık kayıplarının toplamları T6 ısıl işlem görmemiş numunelerle karşılaştırıldığında %30 borakslı %50 haddelenmiş Al7075 numune hariç bütün numunelerin ağırlık kayıplarının T6 ısıl işlemiyle birlikte arttığı gözlemlenmiştir. Potansiyodinamik polarizasyon korozyon deneyi sonuçlarına göre, %30 boraks ilaveli %50 haddelenmiş Al7075 numunesi hariç bütün numunelerin korozyon akım yoğunluğu (Icorr) değerlerinin, 6.29E-06 A değerine sahip ana matris Al7075 malzemesinin numunesinden daha düşük olduğu görülmüştür. T6 ısıl işleminden sonra %30 boraks ilaveli %50 haddelenmiş Al7075 numunesinin Icorr değeri 9.173E-06 A’den 3.76E-06 A’ya kadar düştüğünden bütün malzemelerin ana malzemeye göre korozyon direncinin daha yüksek olduğu gözlemlenmiştir.
In this study, the effect of adding borax (Na?[B?O?(OH)?]·8H?O) to the Al7075 alloy at weight percentages of %15 and %30 via the liquid melt method (stir casting) on the mechanical properties of the alloy was investigated. Boron aluminum compounds were obtained by adding borax to Al7075 alloy in a crucible. The obtained Al7075+%15 borax and Al7075+%30 borax composites were subjected to cold rolling at percentages of %50 and %80. Additionally, some samples were subjected to T6 heat treatment to investigate the effects of precipitation hardening and aging of T6 heat treatment. The spectral analysis, microstructure, Brinell hardness, dry wear, and potentiodynamic corrosion behaviors of the obtained samples were analyzed. After the experiments, EDX analyses and SEM images were taken to examine the phase states on the surfaces of the samples. As a result of the average grain size measurement made on the microstructures taken from Al7075 samples with 15% borax, 30% borax and no borax addition, it was observed that the average grain size increased as the borax addition increased compared to the Al7075 sample (111 µm) without borax addition. When T6 heat treatment was applied to the borax added samples, it was observed that the average grain size decreased (18.8% with 15% borax, 5.5% with 30% borax). When T6 heat treatment is applied after 50% and 80% cold rolling processes, a smaller grain size than that of the Al7075 (111 µm) was obtained. As a result of the hardness measurement, the highest hardness value was observed in the %80 cold-rolled and %15 borax added sample (84.11 BH), while the lowest hardness value was observed in the %30 borax added sample that was cold-rolled at %50 (65.54 BH). After T6 heat treatment, the highest hardness value was observed in the %80 cold-rolled and 30% borax added sample (74.83 BH), while the lowest hardness value was observed in the 30% borax added sample (65 BH). The addition of borax increased the weight loss compared to the Al7075 material with a total weight loss of 0.0223 g however with the increase in borax addition, a decrease in total weight loss was observed in the dry wear results (while it was 0.0336 grams in the 15% borax sample, it decreased to 0.031 grams in the 30% borax sample), resulting in an increase in wear resistance. When these two samples were subjected to T6 heat treatment, the weight loss of the 30% borax added sample decreased by 7.74%, while the weight loss of the 15% borax added sample increased by 42.56%. Cold rolling alone improved the wear resistance of the samples compared to their pre-rolled state. When the total weight losses of the T6 heat-treated samples were compared to those of the samples that were not heat-treated, it was observed that the weight losses of all samples, except for the %50 cold-rolled with %30 borax addition Al7075 sample, increased by the implementing of T6 heat treatment. According to the results of the potentiodynamic polarization corrosion test, it has been observed that the corrosion current density (Icorr) values of all samples except for the %50 cold-rolled with %30 borax addition sample have lower values than the main matrix Al7075 material with a value of 6.29E-06 A. After the T6 heat treatment, the Icorr value of the %30 borax added %50 cold-rolled sample decreased from 9.173E-06 A to 3.76E-06 A, indicating an increase in corrosion resistance for all materials compared to the main material."
In this study, the effect of adding borax (Na?[B?O?(OH)?]·8H?O) to the Al7075 alloy at weight percentages of %15 and %30 via the liquid melt method (stir casting) on the mechanical properties of the alloy was investigated. Boron aluminum compounds were obtained by adding borax to Al7075 alloy in a crucible. The obtained Al7075+%15 borax and Al7075+%30 borax composites were subjected to cold rolling at percentages of %50 and %80. Additionally, some samples were subjected to T6 heat treatment to investigate the effects of precipitation hardening and aging of T6 heat treatment. The spectral analysis, microstructure, Brinell hardness, dry wear, and potentiodynamic corrosion behaviors of the obtained samples were analyzed. After the experiments, EDX analyses and SEM images were taken to examine the phase states on the surfaces of the samples. As a result of the average grain size measurement made on the microstructures taken from Al7075 samples with 15% borax, 30% borax and no borax addition, it was observed that the average grain size increased as the borax addition increased compared to the Al7075 sample (111 µm) without borax addition. When T6 heat treatment was applied to the borax added samples, it was observed that the average grain size decreased (18.8% with 15% borax, 5.5% with 30% borax). When T6 heat treatment is applied after 50% and 80% cold rolling processes, a smaller grain size than that of the Al7075 (111 µm) was obtained. As a result of the hardness measurement, the highest hardness value was observed in the %80 cold-rolled and %15 borax added sample (84.11 BH), while the lowest hardness value was observed in the %30 borax added sample that was cold-rolled at %50 (65.54 BH). After T6 heat treatment, the highest hardness value was observed in the %80 cold-rolled and 30% borax added sample (74.83 BH), while the lowest hardness value was observed in the 30% borax added sample (65 BH). The addition of borax increased the weight loss compared to the Al7075 material with a total weight loss of 0.0223 g however with the increase in borax addition, a decrease in total weight loss was observed in the dry wear results (while it was 0.0336 grams in the 15% borax sample, it decreased to 0.031 grams in the 30% borax sample), resulting in an increase in wear resistance. When these two samples were subjected to T6 heat treatment, the weight loss of the 30% borax added sample decreased by 7.74%, while the weight loss of the 15% borax added sample increased by 42.56%. Cold rolling alone improved the wear resistance of the samples compared to their pre-rolled state. When the total weight losses of the T6 heat-treated samples were compared to those of the samples that were not heat-treated, it was observed that the weight losses of all samples, except for the %50 cold-rolled with %30 borax addition Al7075 sample, increased by the implementing of T6 heat treatment. According to the results of the potentiodynamic polarization corrosion test, it has been observed that the corrosion current density (Icorr) values of all samples except for the %50 cold-rolled with %30 borax addition sample have lower values than the main matrix Al7075 material with a value of 6.29E-06 A. After the T6 heat treatment, the Icorr value of the %30 borax added %50 cold-rolled sample decreased from 9.173E-06 A to 3.76E-06 A, indicating an increase in corrosion resistance for all materials compared to the main material."
Açıklama
Anahtar Kelimeler
Al7075 alaşımı, Boraks, Soğuk Haddeleme, T6 Isıl İşlem, Spektral Analiz, Mikro Yapı, Brinell Sertliği, Kuru Aşınma, EDX Analizi, SEM Görüntüleri, Tane Boyutu., Al7075 alloy, Borax, Cold rolling, T6 heat treatment, Spectral analysis, Microstructure, Brinell hardness, Dry wear, EDX analysis, SEM images, Grain size.
