Effect of La2O3 reinforcement and mechanical alloying on the microstructural and mechanical properties of pressureless sintered Al15Si2.5Cu0.5Mg composites

Abstract

The aim of this work is to synthesize aluminum based metal matrix composites (AMMCs) by reinforcing with lanthanum oxide (La2O3) particles using powder metallurgy route and to characterize them in terms of microstructural/mechanical properties.  In the experimental studies, elemental aluminum (Al), silicon (Si), copper (Cu), magnesium (Mg) and La2O3 powders were blended in order to constitute powder batches with the compositions of Al15Si2.5Cu0.5Mg-x wt.% La2O3 (x=0.5, 1, 2 and 5 wt.%) and they were mechanically alloyed (MA'd) for 4 h.  Then, the as-blended (MA for 0 h) and MA'd (MA for 4 h) powders were compacted with uniaxial cold press under a pressure of 450 MPa and green bodies were conventionally sintered at 570C for 2 h under Ar gas flowing conditions.  Characterizations of the as-blended and MA'd powders and sintered composites were conducted using X-ray diffractometry (XRD) and scanning electron microscopy/energy dispersive spectrometry (SEM/EDS) techniques.  Also, relative densities of the sintered samples were determined using a He gas pycnometer.  Vickers microhardness and wear volume loss values of the sintered samples were measured.  The experimental results showed that microhardness values and wear resistances of the sintered samples increased with increasing La2O3 content.  Al15Si2.5Cu0.5Mg-5 wt.% La2O3 MA’d for 4 h showed the highest microhardness value (172.24±38 HV) and the lowest wear volume loss value (0.115 mm3) among the all samples.

Keywords

• Mechanical alloying
• aluminum based metal matrix composites
• lanthanum oxide
• microstructural/mechanical properties

La2O3 takviyesinin ve mekanik alaşımlamanın basınçsız sinterlenmiş Al15Si2,5Cu0,5Mg kompozitlerinin mikroyapısal ve mekanik özelliklerine etkisi

Abstract

Bu çalışmanın amacı, alüminyum esaslı metal matris kompozit malzemelerin (AMMK) lantan oksit (La2O3) partikülleri ile takviyelendirilmek suretiyle toz metalurjisi yöntemleri kullanılarak sentezlenmesi ve bu kompozitlerin mikroyapısal/mekaniksel özellikler açısından karakterize edilmesidir.  Deneysel çalışmalarda, elementel alüminyum (Al), silisyum (Si), bakır (Cu), magnezyum (Mg) ve La2O3 tozları, Al15Si2,5Cu0,5Mg-x La2O3 (x=ağ.% 0,5, 1, 2 ve 5) kompozisyonlarını oluşturacak şekilde harmanlanmış ve bu tozlar 4 sa süre boyunca birbirleri ile mekanik alaşımlanmıştır (MA).  Takiben, harmanlanmış (0 sa MA) ve mekanik alaşımlanmış (4 sa MA) tozlar 450 MPa basınç altında tek eksenli pres kullanılarak soğuk preslenmiş ve preslenen bünyeler 570C’de 2 sa süre ile Ar gazı altında basınçsız olarak sinterlenmiştir.  Harmanlanmış ve mekanik alaşımlanmış tozların ve sinterlenmiş kompozitlerin karakterizasyonları, X-ışınları difraksiyonu (XRD) ve taramalı elektron mikroskobu/enerji dağılımlı spektroskopi (SEM/EDS) teknikleri ile gerçekleştirilmiştir.  Ayrıca, sinterlenmiş numunelerin rölatif yoğunlukları He gazı piknometresi ile saptanmıştır.  Kompozitlere ait Vickers mikrosertlik değerleri ve aşınma kaybı hacimsel miktarları belirlenmiştir.  Deneysel sonuçlara göre, kompozitlere ait mikrosertlik değerleri ve aşınma dirençleri, La2O3 miktarının artmasıyla artış göstermiştir.  4 sa alaşımlanmış ve sinterlenmiş Al15Si2,5Cu0,5Mg-ağ.% 5 La2O3 kompozit malzemenin, tüm kompozisyonlar içerisinde en yüksek sertliğe (172,24±38 HV) ve en düşük aşınma kaybına (0,115 mm3) sahip olduğu bulunmuştur.

Keywords

• Mekanik alaşımlama
• alüminyum esaslı metal matris kompozitler
• lantan oksit
• mikroyapısal/mekanik özellikler

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