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Study On Microstructure And Properties Of Fe-Cr-B-Al Alloy

Posted on:2014-08-30Degree:MasterType:Thesis
Country:ChinaCandidate:Z YuFull Text:PDF
GTID:2251330392973329Subject:Materials Science and Engineering
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In this article, we have designed eight kinds of different Fe-Cr-B-Al alloycontaining X wt.%Al-0.35wt.%C-1.4wt.%B-10wt.%Cr-0.6wt.%Si and-0.8wt.%Mn (X=0,0.5,1.0,1.5,2.0,2.5,3.0,4.0). Optical microscopy (OM), Scanningelectron microscopy (SEM) and X-ray diffraction (XRD) were used to study themicrostructure of Fe-Cr-B alloy made by metal mode casting, and its mechanicalproperties and wear resistance were studied by Rockwell hardness tester,micro-hardness tester, impact toughness tester and abrasive wear tester. The wearmechanisms of alloy at room and high temperature condition were also explored.The experimental results showed that the matrix of Fe-Cr-B alloy solidificationstructure was composed of martensite, residual austenite and different types of boroncarbon compounds, hardness of Fe-Cr-B alloy was higher than65HRC. Whenaluminum concentration was no more than1.0%, the hardness and phase compositionof the alloy had no significant change. As aluminum content was above1.5%, anumber of pearlite and a small amount of ferrite appear in the matrix. The hardnessfell sharply to39.7HRC. When aluminum content increased continuously, theproportion of ferrite in the matrix was markedly increased and the hardness ofFe-Cr-B-Al alloy had no obvious change. The network eutectic phase fractured moreobviously with the increase of quenching temperature. As the secondary precipitatephase grew up and got together, some eutectic phase tended to be spheroidized. Whenthe aluminum content was less than1.5%, hardness of Fe-Cr-B-Al alloy risesuniformly with the increase of quenching temperature. When the aluminum contentwas more than1.5%, massive ferrite and pearlite in the matrix transformed intomartensite; hardness of alloy had risen sharply in a quenching temperature interval,and the range of temperature is higher along with the increase of aluminium content.Under this experimental condition, hardness of samples containing1.5%aluminumquenching at1100℃is the highest. Highest hardness of the alloy was66HRC.Hardness of both Fe-Cr-B alloy and Fe-Cr-B-2.0Al alloy declined with the increase oftempering temperature. The addition of aluminum slowed down the temper softeningof alloy. Fe-Cr-B-2.0Al alloy tempered at500℃can still keep in high hardness morethan61HRC. Fe-Cr-B-Al alloy. Along with the increase of the aluminum content, theimpact toughness of Fe-Cr-B-Al alloy went up at first and then went down. When the aluminum content reached4.0%, impact toughness dropped significantly. The wearmechanisms of pin-on-disk wear test in room temperature were plastic sheardeformation and ploughing wearing. Wear resistance of Fe-Cr-B-Al alloy was up andthen descended with the addition of aluminum. Under the condition of this experiment,samples with2.0%aluminum had the best wear resistance. Wear mechanisms in hightemperature were very complicated, simultaneously accompanied by adhesive wear,abrasive wear and surface oxidation. Wear resistance of Fe-Cr-B-Al alloy in hightemperature improved with the increase of aluminum content. Samples with2.5%aluminum in high temperature had the beat wear resistance, which was enhanced52.7%than that of the Fe-Cr-B alloy without aluminum.
Keywords/Search Tags:Fe-Cr-B-Al alloy, aluminum content, heat treatment, microstructure, mechanical properties, wear resistance
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