Preparation And Study On Properties Of B₄C/Al Matrix Composites

With the development of nuclear power applications in our country,the production of highly radioactive spent fuel will increase substantially,and its storage and transportation problems need to be sloved urgently.Currently,boron and boron aluminum alloys in the market cannot meet the high density storage and transportation of spent fuel.The new B₄C_p/Al composites have good neutron absorbing ability and excellent mechanical properties,which can meet the high density storage and transportation of spent fuel.However,the existing preparation technology was not perfect,and the key factors that affect the mechanical properties were not systematically studied.In addition,the hot working of B₄C_p/Al was more difficult due to the presence of the strengthening phase B₄C particles,which to a certain extent hindered mass production of B₄C_p/Al composites.Therefore,how to choose the appropriate processing technology and improve the production efficiency of B₄C_p/Al is an urgent problem to be solved.In this thesis,31wt.%B₄C_p/Al composites with different B₄C particle sizes were prepared by powder metallurgy.The effects of B₄C particle size on the properties and interface reaction of composites were studied at different matrix and hot-pressed temperatures,and the hot compression tests of 31wt.%B₄C_p/6061Al composites with B₄C particle 28?m hot pressed at580?C were done to study hot deformation behavior.By means of OM,SEM,XRD,EPMA and TEM,the relationship between the evolution of composites,the state of interface reaction and performance was studied systematically.And the relationship between thermal deformation behavior and microstructure was also analyzed.The main research results are as follows:?1?31wt.%B₄C_p/Al composites with different B₄C particle sizes were prepared at hot-pressing temperature 610?C.Density reached more than 90%,B₄C_p evenly distributed in the matrix.Broken B₄C particles appeared in the composites of large particle size.Moreover,with the increase of B₄C_p size,the density and ductility of composites increased and the strength decreased.?2?31wt.%B₄C_p/6061Al composites with different B₄C particle sizes were prepared at hot-pressing temperature of 610?C.The density of composites reached above 99.5%,B₄C_p distributed uniformly.The phenomenon of particle breakage became weaker.There was a serious interfacial reaction on the composite interface.The interfacial reaction products contained not only the Al₃BC,but also the product phase containing Mg element.In addition,the strength of the composites increased obviously,and the ductility decreased obviously because of the addition of alloy element.With the increase of the size of B₄C_p,the density of the composites decreased,and the strength decreased first and then increased,while the ductility increased first and then decreased;the interface reaction gradually decreased,and the interface reaction phase Al₃BC and MgAl₂O₄ gradually decreased.After T6 heat treatment,the strength of composites was improved.?3?31wt.%B₄C_p/6061Al composites with different B₄C particle sizes were prepared at hot-pressing temperature of 580?C.The density of composites was also above 99.5%.With the increase of B₄C_p size,compared to hot-pressing temperature 610?C,its density and strength decreased,while the ductility improved significantly.In terms of interface reaction,the interfacial reaction was significantly reduced,and no product phase containing Mg was found,and with the increase of B₄C_p,the content of Al₃BC decreased.After T6 heat treatment,the strength of composites increased greatly.?4?According to the stress-strain curves,the maximum stress value of composites decreased with the increase of deformation temperature under the same strain rate.Through processing map and microstructure,the optimal hot working parameters of 31%B₄C_p/6061Al composites is:the deformation temperature 470⁴95?C,the strain rate 0.001⁰.002s^-1.