Stronsiyum ve stronsiyum-magnezyum katkılarının ötektiküstü Al-17Si alaşımının içyapı ve mekanik özelliklerine etkisi

Yıl 2019, Cilt: 25 Sayı: 1, 49 - 55, 26.02.2019

Ali Paşa Hekimoğlu , Gizem Ayata

Öz

Al-17Si,
Al-17Si-0,1Sr ve Al-17Si-0,1Sr-0,6Mg alaşımları kokil kalıba döküm yöntemi ile
üretilmiştir. Alaşımların yapısal ve mekanik özellikleri üretilen alaşım külçelerinden
talaşlı imalat yöntemiyle hazırlanan numuneler üzerinde yapılan incelemeler ile
belirlenmiştir. İçyapı incelemeleri standart metalografik yöntemler ile
hazırlanan ancak dağlama yapılmayan numuneler üzerinde gerçekleştirilmiştir. İncelenen
alaşımların sertlik değerleri Brinell sertlik ölçüm yöntemi, mekanik özelikleri
ise üniversal bir çekme deneyi makinesinde yapılan testler yardımıyla belirlenmiştir.
İkili Al-17Si alaşımının içyapısının alüminyumca zengin α dendiritleri, primer
silisyum, ötektik Al-Si ve β fazlarından oluştuğu, üçlü Al-17Si-0.1Sr
alaşımının içyapısının ise ikili Al-17Si alaşımındaki fazlara ek olarak Al_xSi_ySr_z
fazını içerdiği görülmüştür. Üçlü Al-17Si-0.1Sr alaşımına %0.6 oranında yapılan
magnezyum katkısının ise bu alaşımın içyapısında Mg₂Si fazının
oluşmasına yol açtığı gözlenmiştir. Al-17Si alaşımının sertlik, akma dayanımı,
çekme dayanımı ve kopma uzaması değerleri sırasıyla 57 BSD, 93.7 MPa, 127.6 MPa ve %2.4, olarak ölçülmüştür. Bu değerler
Al-17Si-0,1Sr alaşımında 55 BSD, 95.2 MPa, 137.9 MPa ve %2.9, Al-17Si-0.1Sr-0.6Mg alaşımında ise sırasıyla 70 BSD, 123.2 MPa, 141.1 MPa ve %1.1
olarak ölçülmüştür. Stronsiyum katkısının ikili Al-17Si alaşımının sertliğini
çok az da olsa düşürdüğü, akma ve çekme dayanımı ile kopma uzaması değerlerini
ise iyileştirdiği görülmüştür. Magnezyum katkısının ise üçlü Al-17Si-0.1Sr
alaşımının akma ve çekme mukavemetini önemli ölçüde artırdığı ancak, kopma
uzamasını azalttığı belirlenmiştir. Stronsiyum ve stronsiyum-magnezyum
katkılarının Al-17Si alaşımının mekanik özelliklerine etkisi alaşımların
yapısal özelliklerine dayandırılarak açıklanmıştır.

Anahtar Kelimeler

Al-17Si esaslı alaşımlar, İçyapı, Mekanik özellikler

Effect of strontium and strontium-magnesium additions on the microstructure and mechanical properties of hypereutectic Al-17Si alloy

Öz

Al-17Si, Al-17Si-0,1Sr and Al-17Si-0.1Sr-0,6Mg alloys were produced by
permanent mold casting method. The structural and mechanical properties of the
alloys were determined by the investigations carried out on specimens prepared
by machining of the produced alloy ingots. The microstructural examinations
were carried out on specimens prepared by standard metallographic methods but
without etching. Their hardness and mechanical properties ​​were determined by
Brinell hardness measurement method and universal tensile tests, respectively.
The microstructure of the binary Al-17Si alloy consisted of aluminum-rich α dendrites, primary silicon, eutectic Al-Si and βphases. Ternary
Al-17Si-0.1Sr alloy contained Al_xSi_ySr_z phase
in addition to phases in the binary Al-17Si alloy. It was observed that the
0.6% magnesium addition to the ternary Al-17Si-0.1Sr alloy cause to form of Mg₂Si
phase in the microstructure of this alloy. The values of the hardness, yield
strength, tensile strength and elongation to fracture of Al-17Si alloy were
measured as 57 BSD, 93.7 MPa, 127.6 MPa and 2.4%, respectively. These values
were measured as 55 BSD, 95.2 MPa, 137.9 MPa and 2.9% in Al-17Si-0.1Sr alloy and 70 BSD, 123.2 MPa, 141.1 MPa and
1.1% in Al-17Si-0.1Sr-0.6Mg alloy. The addition of strontium reduced the
hardness of the binary Al-7Si alloy to a lesser degree but improved the yield
and tensile strength and elongation to fracture values. Magnesium addition
significantly increased the yield and tensile strength of the ternary
Al-17Si-0.1Sr alloy but decreased their elongation to fracture. The effects of
strontium and strontium-magnesium additions on the mechanical properties of the
Al-17Si alloy were discussed in terms of their structural properties. 

Anahtar Kelimeler

Al-17Si based alloys, Microstructure, Mechanical properties

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