基体铝合金成分对无压浸渗B4C/Al复合材料微观组织和力学性能的影响

The Effect of Matrix Aluminum Alloy Composition on Microstructure and Mechanical Properties of B4C/Al Composites by Pressureless Infiltration

分别选用2024、5056、6061和7075铝合金,采用颗粒级配相同的碳化硼预制体(20%2μm和80%38μm)为增强体,采用无压浸渗法制备4种高体份B4C/Al复合材料(分别对应标记为2M、5M、6M和7M),研究基体合金成分对复合材料的物相组成、微观组织和力学性能的影响。结果表明,4种复合材料均含有A1、B4C、Al3BC、AlB2和富Fe-Mn相,除此之外,2M、5M和7M复合材料还含有Al B10。4种复合材料小颗粒碳化硼聚集区均发生了剧烈的界面反应,生成Al3BC和Al B2。Al B10主要分布于2M、5M和7M复合材料的大颗粒碳化硼周围,并与大颗粒碳化硼连成一体。4种复合材料的洛氏硬度从大到小顺序为2M(45. 7)、7M(43. 1)、5M(41. 8)和6M(40. 02)。2M、5M和7M复合材料内部发现有孔洞存在,导致复合材料弯曲强度和应力均较低。这种效应在7M复合材料中最为明显,其弯曲强度仅为296 MPa。6M复合材料弯曲强度和应变最高,分别为425 MPa和0. 183%,这主要是因为在6M复合材料中,不含Al B10相且残余铝合金相对含量较高。

Four kinds of high volume fraction B4C/Al composites were prepared by pressureless infiltration using four different aluminum alloys( 2024 Al,5056 Al,6061 Al and 7075 Al) and B4C preform with the same particle-size distributions(20% 2 μm and 80% 38 μm),which were named as 2M,5M,6M,and 7M,respectively. The effect of matrix alloy composition on the phase composition,microstructure and mechanical properties of the composites was investigated. The results show that all of the composites contain A1,B4 C,Al3 BC,AlB2,and Fe-Mn-rich phases. Besides,2 M,5 M,and 7 M composites also contain the additional phase,Al B10. For all of the composites,the severe interfacial reaction occurred in the aggregation areas of the small B4 C particle,with the formation of Al3 BC and Al B2. Al B10 is mainly distributed around large B4 C particles in 2 M,5 M and 7 M composites and is integrated with large B4 C particles. The Rockwell hardness of the four composites decreased in the sequence 2 M( 45. 7),7 M( 43. 1),5 M( 41. 8) and 6 M( 40. 02). The micropores are observed in the 2 M,5 M,and 7 M composites,resulting in the decrease of the flexural strength and fracture strain of the corresponding composites. Accordingly,7 M composite possesses the lowest flexural strength,being about 296 MPa. Conversely,the flexural strength and fracture strain of the 6 M composite are the highest,being about 425 MPa and 0. 183%,respectively. This could be mainly attributed to the absence of Al B10 phase and the highest fraction of the residual aluminum matrix in the 6 M composite.