Synthesis and Characterization of Mechanically Alloyed and HIP-Consolidated Fe-25Al-10Ti Intermetallic Alloy
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Synthesis and Characterization of Mechanically Alloyed and HIP-Consolidated Fe-25Al-10Ti Intermetallic Alloy Su-Ming Zhu, Makoto Tamura, Kazushi Sakamoto and Kunihiko Iwasaki Japan Ultra-high Temperature Materials Research Institute, Ube, Yamaguchi 755-0001, Japan
ABSTRACT The present study is concerned with the processing, microstructural characterization, mechanical and tribological properties of fine-grained Fe-25Al-10Ti intermetallic alloy. The alloy was synthesized from elemental powders by mechanical alloying in an attritor-type ball milling system for 100 h, followed by hot isostatic pressing (HIP). After HIP treatment at 1073 K under an ultra-high pressure of 980 MPa, fully dense compacts with a grain size of about 200 nm were produced. Mechanical properties were evaluated by compression tests from room temperature to 1073 K. At room temperature, the alloy exhibits yield strength as high as 2.4 GPa, together with considerable rupture strain of 0.16. The yield strength decreases monotonically with increasing test temperature with no positive temperature dependence observed. The grain growth after high temperature deformation is not severe, indicating that the alloy has a relatively high thermal stability. Finally, tribological properties of the alloy were evaluated by using a ball-on-disk type wear tester and compared with those for gray cast iron, a currently used material for automotive brake rotors.
INTRODUCTION Recently, there is some interest in studying the wear properties of iron aluminide based on Fe3Al [1-3]. The aluminide possesses many attributes necessary for wear resistance - high hardness, high elastic modulus and good environmental resistance, and are thus promising as tribological materials for use in aggressive environments at elevated temperatures. Moreover, in wear related applications, tensile ductility is not so crucial since loads are compressive in nature. It has been shown that Fe3Al has wear resistances similar to those of a variety of steels, for example 304 SS [1]. To improve the wear resistances of Fe3Al, Hawk et al. [2] have examined the alloying effects of Ti, Zr, Cr, Ni, Nb and Mo. They demonstrated that additions of Ti to Fe3Al have a positive influence on their tribological properties. For example, the alloy with 10 at. % Ti substituting for Fe in Fe3Al shows 40% decrease in volume wear compared with Fe3Al. However, as pointed out by some researchers [4,5], the addition of Ti into iron aluminides tends to reduce the room temperature ductility, which makes the processing and machining very difficult. Mechanical alloying has been extensively exploited in the synthesis and processing of intermetallic compounds in recent years [6]. Mechanical alloying is a high-energy ball milling process which involves repeated welding and fracturing of powder particles. This technique can produce fine powders with a nanoscale grain size and a homogeneous distribution of dispersoids, which is expected to improve the ambient temperature ductility and high temperature strength of intermetallic co
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