Fabrication And Corrosion Behavior In Molten Aluminum Of Iron-based Composites Reinforced With Intermetallics

During melting and casting of aluminium alloy,hot-dip-aluminizing and preparation of aluminum alloy parts,components which are in direct contact with molten aluminum,such as crucibles,sink roll and dies,usually fail due to corrosion related to molten aluminum,thereby leading to Al melt pollution,low product quality and increased production cost.Therefore,to develop new materials with good corrosion resistance in molten aluminum and increase the service life of components in direct contact with molten aluminum is of great importance.In this work,three high-Mn high-Al iron-based composites reinforced with intermetallics of?Fe,Mn?₃AlC_x/Fe-Mn-Al-Cr,M₂B/Fe-20Mn-15Cr-8Al and TiB₂/Fe-20Mn-15Cr-8Al have been fabricated by the combination of mechanical alloying?MA?and spark plasma sintering?SPS?.After investigating the microstructure and mechanical properties,the corrosion resistance and behavior in molten aluminum of three composites were investigated.The main conclusions are as follows:1.Three composites of?Fe,Mn?₃Al C_x/Fe-Mn-Al-Cr,M₂B/Fe-20Mn-15Cr-8Al and TiB₂/Fe-20Mn-15Cr-8Al prepared by SPS at 1100°C under 50 MPa possess ultra-fine grains structures,and all reinforcements distribute uniformly in the matrix.?Fe,Mn?₃AlC_x/Fe-Mn-Al-Cr composite consists of?-Fe?Cr,Mn,Al,C?,?Fe,Mn?₃AlC_x and Cr₇C₃.M₂B/Fe-Mn-Al-Cr composite consists of?-Fe?Cr,Mn,Al,B?,Fe₂AlCr,CrFeB and Mn₂B.TiB₂/Fe-20Mn-15Cr-8Al composite consists of Fe₂AlCr,CrFeB,Mn₂B and TiB₂.The combination of high contents of Al,C and Mn in the matrix as well as application of MA and SPS play a key role in the precipitating of?Fe,Mn?₃AlC_x,Cr₇C₃,Fe₂AlCr,CrFe B and Mn₂B.2.All the three high-Mn high-Al iron-based composites reinforced with intermetallics prepared by SPS exhibit high hardness and strength at room temperature,which are attributed to the solid-solution strengthening,grain-boundary strengthening and dispersion strengthening.Within 15³0 vol.%,with the increase of M₂B and TiB₂ content in the matrix,the hardness and compressive strength of M₂B/Fe-20Mn-15Cr-8Al and Ti B₂/Fe-20Mn-15Cr-8Al composites increase,whereas the compressive plastic deformability decrease.The hardness and compressive strength of 30 vol.%TiB₂/Fe-20Mn-15Cr-8Al composite is 767 HV and 2835 Mpa,respectively,which is the highest among all the composites.The fracture strain of 15 vol.%M₂B/Fe-20Mn-15Cr-8Al composite is²3.9%,which is the highest among all the composites.3.The?Fe,Mn?₃AlC_x/Fe-Mn-Al-Cr composite exhibits the best corrosion resistance in Al melt among the three composites,and its average corrosion rate in 750°C Al melt for 8 h is21%of that of H13.Besides the dense crystal structure of?-Fe?Cr,Mn,Al,C?,no reaction between molten aluminum and reinforcements of?Fe,Mn?₃AlC_x and Cr₇C₃ is the important factor.4.The average corrosion rate of 30 vol.%M₂B/Fe-20Mn-15Cr-8Al composite in 750°C Al melt for 8 h is 32%of that of H13.In addition to that the dense crystal structure of?-Fe matrix can slow the corrosion rate,the corrosion products of Al-Fe-Cr-Mn-B and FeAl₃resulted from reaction of two rich-Cr boride?CrFeB and Mn₂B?with Al melt formed periodic lamellar structure?PLS?with two phases alternately arranged,which exhibit excellent corrosion resistance in Al melt and act as roots to prevent corrosion products from spalling.