原位合成TiB2对B4C/2024Al合金复合材料组织与力学性能的影响

在B4C粉末中加入5%高纯TiO2,经过压制和烧结制备B4C-TiB2陶瓷预制体,然后在氩气气氛中1 200℃下浸渗2024铝合金制得B4C-TiB2/Al合金复合材料。对该复合材料进行力学性能测试、X射线衍射分析、显微组织观察和断口分析。结果表明:该复合材料主要由B4C,Al,Al3BC和AlB2相组成,原位合成的TiB2使B4C/Al合金复合材料的抗弯强度和断裂韧性显著提高,分别达到361 MPa和7.49 MPa m1/2,增幅分别为14.6%和11.5%,但密度变化很小。原位合成TiB2使B4C/Al合金复合材料的抗弯强度和断裂韧性提高主要来源于金属铝塑性变形的裂纹桥接机制、TiB2细化晶粒及微裂纹引起的主裂纹偏转分叉机制。

Effect of in situ synthesized TiB2 on microstructure and mechanical properties of B4C/2024 Al alloy composites

B4C-TiB2/Al composites were fabricated at 1 200 ℃ by pressureless melt infiltration of 2024 aluminum alloy under Ar atmosphere into porous B4C green compacts added with 5%(mass fraction) high purity TiO2 which were prepared by presintering.Mechanical properties of the composites were tested.The phase composition and microstructure of B4C-TiB2/Al alloy composites were determined by X-Ray diffraction(XRD) and scanning electron microscope(SEM).The results show that main phases of the composites are B4C,Al,Al3BC and AlB2.The in-situ synthesized TiB2 can effectively improve the mechanical properties of the B4C-TiB2/Al composites.The value of bending strength and fracture toughness of B4C-TiB2/Al alloy composites are 361 MPa and 7.49 MPa.M1/2which are 14.6% and 11.5% higher than that of B4C/Al composites.The mechanisms of mechanical property increasing include crack bridging mechanism of Al plastic deformation,TiB2grain refinement and crack deflection and branching.