Investigation On Microstructure And Properties Of In-situ TiB₂/Cu Composite

Due to the good mechanical properties and good electrical conductivity of TiB2,TiB2/Cu composites can be prepared with TiB2 and copper,which has shown a good application prospect in industry.In this subject,TiB2/Cu composites were prepared by in-situ reactive method wih Cu-Ti-B,Cu-Ti-B4C,Cu-TiH2-B three different systems,including vacuum arc melting method and hot-pressing method.The phase constituents of TiB2/Cu composites were characterized by XRD.The microstructure of composites and the morphology,size and distribution of TiB2 were characterized by means of SEM and TEM.The hardness,electrical conductivity and relative density of TiB2/Cu composites were tested and analyzed.The conclusion is as follows:(1)For Cu-Ti-B system,TiB2/Cu composites were prepared by arc melting method.In the composites,the aggregation of TiB2 particles shows as the plum blossom shape and the distribution of TiB2 is uneven.The size of TiB2 particles is micron scale.The hardness of the composites increases and the electrical conductivity decreases with increase of TiB2 content.For 5wt.%TiB2/Cu composites,after vacuum inductiom melting,the electrical conductivity increases by 73%while the hardness decreases;after cold deformation processing,the hardness and electrical conductivity increase by 32%and 59%,respectively.(2)For Cu-Ti-B,Cu-Ti-B4C,Cu-TiH2-B system,TiB2/Cu composites were prepared by hot-pressing method.With lower TiB2 content of TiB2/Cu composites,the particles distribute homongensenly in copper matrix,while with higher TiB2 content,an obvious aggregation occurs.The morphology of TiB2 particles is hexagon and the size of TiB2 particles mainly is nanoscale.TiC particles are generated in Cu-Ti-B4C system,the morphology is similar to the spherical shape and the size is nanoscale.A small amount of TiB whiskers is generated in Cu-TiH2-B system,the morphology is short rod and the diameter is about 100nm and the length is micron scale.(3)For TiB2/Cu composites prepared by hot-pressing method,the hardness of the composites increases and the electrical conductivity decreases with increase of TiB2 content.Compared with Cu-Ti-B and Cu-Ti-B4C system,the hardness and electrical conductivity of TiB2/CU composites prepared with Cu-TiH2-B system are improved while the relative density is also maintained at a higher level.(4)The reaction mechanism of Cu-TiH2-B system can be described as:in the process of heating dehydrogenation,the phase change prosess of TiH2 is TiH2-TiH1.5->Ti;Then solid diffusion reaction occurs between Cu and Ti,and Cu3 intermetallic compounds are generated;Finally,TiB2 particles and a small amount of TiB whiskers ate generated by the reaction between B and Ti atoms of CU3Ti.The copper matrix is also involved in the whole in-situ reaction process.The reaction mechanisms of Cu-Ti-B and Cu-Ti-B4C system are similar to the reaction mechanism of Cu-TiH2-B system.