Abstract




 
   

IJE TRANSACTIONS A: Basics Vol. 31, No. 1 (January 2018) 19-24   

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  FRACTURE MECHANISM OF COCRMO POROUS NANO-COMPOSITE PREPARED BY POWDER METALLURGY ROUTE
 
M. Taghian Dehaghani and M. Ahmadian
 
( Received: August 14, 2017 – Accepted in Revised Form: November 30, 2017 )
 
 

Abstract    The main aim of this research was to find the mechanism for the failure of the CoCrMo porous nano-composite by characterizing microstructural changes and fractured surface after compression test. For this purpose, porous nano-composites were prepared with the addition of bioactive glass nano-powder to Co-base alloy with 22.5% porosity by the combination of space-holder and powder metallurgy techniques. The micrographs of samples showed that porous nano-composites had the micro and macro pores including open and closed pores. The observed fracture surface in the triple conjunction of sintered powders indicated a complex of intergranular and transgranular fracture mechanisms. The brittle carbide phase related to the higher solute content (Cr and Mo) precipitated at grain boundaries, leading to the intergranular fracture mechanism and transgranular mechanism that was due to the phase transformation during compression test.

 

Keywords    nano-composite, porosity, fracture mechanism, microstructure, powder metallurgy.

 

چکیده    هدف اصلي از اين تحقيق یافتن سازوکار (مكانيزم) شكست نانوكامپوزيت متخلخل CoCrMo با مشخصه­يابي تغييرات ساختاري و سطح شكسته شده بعد از آزمايش فشار بود. براي اين منظور، نمونه­هاي نانوكامپوزيت با تلفيقي از روش­هاي متالورژي پودر و استفاده از ماده­ي فضاساز با افزودن نانوپودر شيشه زيست­فعال به آلياژ پايه كبالت و رسيدن به تخلخل 5/22% ساخته شد. تصاوير ميكروسكوپي نمونه­ها نشانگر وجود ميكرو و ماكرو تخلخل­ها، با ساختار باز و بسته بود. مشاهده سطح شكست در نواحي تف­جوشي سه­تايي پودري، تركيبي از مكانيزم شكست بين­دانه­اي و داخل دانه­اي را نشان مي­داد. رسوب فاز كاربيدي ترد نتيجه­ي انحلال مقادير بالاي عناصر محلول (كبالت و موليبدن) منجر به مكانيزم شكست بين دانه­اي و تحول فازي در حين كرنش در طول آزمايش فشار منجر به مكانيزم شكست داخل دانه­اي شده بود.

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