摘要
采用原位合成法制备了TiB_2/ZL111复合材料,并对铸态及T6态TiB_2/ZL111复合材料的显微组织及硬度进行了研究。结果表明:显微组织方面,铸态TiB_2/ZL111复合材料主要由α-Al、共晶Si和TiB_2组成,TiB_2颗粒平均尺寸为1μm,呈六边形或卵圆形分布于α-Al晶界处;TiB_2有效细化了ZL111的α-Al晶粒,使长条状共晶Si向等轴状转变;T6热处理使共晶Si进一步演变为近球状,并有效改善了TiB_2的团聚现象。硬度方面,TiB_2含量越高,铸态TiB_2/ZL111复合材料的硬度越高,铸态10%TiB_2/ZL111(质量分数)复合材料的维氏硬度(120.13Hv)比铸态ZL111合金(96.63Hv)提高了24.32%;T6热处理使ZL111合金及TiB_2/ZL111复合材料的硬度进一步提高,但硬度提高率随TiB_2含量的增大而减小,TiB_2消弱了T6热处理的时效硬化作用,归因于TiB_2颗粒抑制了Al_2Cu相的析出。
TiB_2/ZL111 composites were prepared by in-situ synthesis method,and their microstructure and hardness in both as-cast and T6 heat treatment states were systematically investigated. The results of microstructure observation show that the phase components of the as-cast TiB_2/ZL111 composites are mainly composed of α-Al,eutectic Si and TiB_2. The TiB_2 particles are hexagonal or oval in shape,with an average crystalline grain size less than 1 μm,and distribute at the boundary of α-Al grains. The addition of TiB_2 can effectively refine the α-Al grains in ZL111 alloy,and change the morphology of eutectic Si form elongated shape to equiaxed shape. T6 heat treatment can further promote the morphological transformation of eutectic Si from equiaxed shape into subglobose shape,and effectively improve the TiB_2 agglomeration phenomenon. The results of hardness measurement show that the higher the TiB_2 content,the higher the hardness of the TiB_2/ZL111 composites in the as-cast state.The hardness of 10 wt % TiB_2/ZL111 composites( 120. 13 Hv) rises by 24. 32%,compared with the hardness of as-cast ZL111 alloy( 96. 63 Hv).The hardness of ZL111 alloy and TiB_2/ZL111 composites can be further improved by taking T6 heat treatment. However,the increase rate of hardness decreases with the increasing of TiB_2 content. This is attributed to the fact that TiB_2 inhibit the precipitation of Al2 Cu during aging process that can result in reducing the aging hardening effect of T6 heat treatment.
引文
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