Study Of Nial-based Porous Composites Prepared By Shs

NiAl-based Intermetallic Compounds have a series of excellent properties,such as high melting point,low density,high heat conductivity,good oxidation resistance and excellent high temperature stability,etc.As a result,it is possible to be used in worse environment or in higher temperature instead of Ni-based and Fe-based high-temperature alloys.To improve the high temperature strength,NiAl-based porous compounds with ceramics reinforce particles were prepared,which can be used in the area of automotive exhaust purification and industrial waste disposal.In this paper,Ni,Al powder as raw material,the high porosity NiAl porous materials were prepared by SHS.Different proportions of Al,TiO₂,B₂O₃ were mixed with Ni,Al powders,and thus TiB₂,Al₂O₃ ceramics reinforce particles are formed in-situ to enhance the high temperature strength of NiAl intermetallic compounds.Besides,TiH₂ was used as foaming agent and adding different ratio of it can improve porosity,hole size and pore structure to meet different requirements of carriers with different conditions of automobile exhaust purification,and thus the best test preparation process is determined.After the combustion synthesis process,the mainly product phases of Ni-Al reaction system is NiAl phase.The particles of products accumulate to deposit.The pore structure is complex and irregularly shaped,which has three-dimensional connectivity,circuitous channels and rough walls.According to the experiment,porous NiAl has a porosity of 28.8%,a low compression strength of 15.24 N/mm² and a micro hardness of HV223.74.After synthesis process,the main phases of the reaction system with different proportions of Al,TiO₂ and B₂O₃ particles are NiAl,Al₂O₃ and TiB₂.The expected porous composites are obtained.Porous composite materials synthesized are granular packs,and the particles are smaller than those NiAl porous materials without addition.The more addition of enhancement system,the smaller particles are.The porosity is increasing obviously,but it is changed a little comparing 10wt% and 20wt% ceramics added.With the addition of 10Al+3TiO₂+3B₂O₃ enhancement system,the compression strength and microhardness of NiAl/(TiB₂+Al₂O₃) porous composite materials are increased on the conditions with similar porosity.And the more addition,the higher of the compression strength and microhardness are.The porosity of the product increases more than 50% after different proportion TiH₂ added.The pore size is even more uneven.Macropores are detected.The pore channels are complex,and the connectivity is better than before.Porosity change curve shows that at first the porosity of the product rises consistently with the proportion of TiH₂,and the maximum appears at 2-3wt% TiH₂．Then it drops as the content of TiH₂ increases,but the dccreaseamplitude is not so obvious．Since adding TiH₂,the hole waIl of the product shows anexcellent metallurgical combination,and the whole strength of the sample improves a lot dueto Ti participated in reaction．It's about 1.5-2.8 times of the products by adding sugar asfoaming agent．This is consistent with the compression test．The basic research work has practical significance for guiding the optimization ofpreparation technology and obtaining porous materiaIs with excellent performance．...