Study On Microstructure And Properties Of Extuded TiBw/TC4Composites After Heat Treatment

In this paper, the large size TC4powders and fine TiB2are sintered by in situtechnique? low energy ball milling and hot-pressing sintering processes. Thereaction product TiB whiskers are reticular distributed in the TiBw/TC4composites.The plastic of the Titanium matrix composites is excellent because of low levels ofTiBw. The composites were deformed by hot extrusion, then heat treatmented byannealing and quench aging. The microstructure of extrusion and heat treatmentstate composite material are studied by using OM and SEM. The tensile propertiesof composites at both room and high temperatures were measured.Whisker extruded composites showed obvious orientation distribution alongthe extrusion direction. Because the reinforcement content is low, the matrix iscommunicated unhindered. The matrix organization of extruded composite materialsis crooked basketweave microstructure with low aspect ratio, this is caused by alarge amount of heat deformation. After two-phase region heat insulating andfurnace cooling, the matrix organization transformed into intergranular structure.Obtain lamellar microstructure coarsening by two-phase region heat preservationand air cooling. Thermal insulation temperature increasing made the organizationmore finely. Appropriate prolonging holding time can make the matrix organizationmore uniform. After two-phase region heat insulating at a high temperature andquench, a lot of ? phase rapid cooling transformation to martensite ', the contrast ofand martensite is low. Aging treatment makes martensite decomposition, obtainand dispersed (+?) aging microstructure.Strength and ductility of extruded composite compared to the sintered haveimproved significantly. The yield strength of2vol.%TiBw/TC4composite reached1048MPa, the tensile strength reached1260MPa, with an elongation of15.74%.After furnace cooling annealing, the strength and plastic of composite dropped. Aircooling annealing can reduce the strength, the strength of2vol.%TiBw/TC4composite dropped by200MPa,by air cooling after900?for1.5hours, while theplastic keep well. The annealing process is effective in other group samples. In orderto obtain tissue and performance that in requirements, the time of heat preservationshould be prolong.Quench aging increase the strength of composite, and keep the plasticsubstantial. The yield strength of2vol.%extruded TiBw/TC4composite reached1235MPa after aging, the tensile strength reached1371MPa, with an elongation of11%.Strengthening effect of ultra-low volume fraction composites is moresignificant, and the plastic damage is less. Heat treatment process of TMCs is different from that of titanium alloy. Thispaper summarizes the optimal annealing and quench aging process of extrudedtitanium matrix composites, obtain excellent processing performance andmechanical properties, and keep a good plasticity.