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摘要:
添加质量分数3%金刚石颗粒并利用激光粉末床熔融技术制备6061铝基复合材料。采用光学显微镜、扫描电子显微镜、X射线衍射仪、电子密度计、电子式万能试验机对3%金刚石/6061铝基复合材料的微观组织、相对密度和拉伸性能进行了表征与分析。结果表明：金刚石与Al基体反应生成了针状Al4C3相，并沉积在α-Al基体上，导致晶界位错密度增加，强度提高，抗失效能力增强。金刚石的添加促使6061铝基体中热裂纹消失，但存在孔洞缺陷。较低的扫描速度增加了激光光斑与被加工材料接触的时间，导致金刚石颗粒部分石墨化，铝基体部分蒸发，进而形成内部缺陷，降低了复合材料的相对密度（97%）。金刚石的加入显著提高了激光粉末床熔融技术成形金刚石/6061铝基复合材料的抗拉强度，当激光功率为350 W、扫描速度为800 mm·s−1时，复合材料的极限抗拉强度达到最大值244.2 MPa，屈服强度211.6 MPa，伸长率2.1%。
Abstract:6061 aluminum matrix composites added by 3% diamond particles (mass fraction) were prepared by laser powder bed fusion (LPBF). The microstructure, relative density, and tensile properties of the 3%diamond/6061 aluminum matrix composites were characterized and analyzed by optical microscope, scanning electron microscope, X-ray diffractometer, electronic densitometer, and electronic universal testing machine. Results show that the diamond reacts with the Al matrix, generating the needle-like Al4C3 phase, which deposits in the α-Al matrix. Those formed Al4C3 increases dislocations at the grain boundaries, enhances the materials’ strength, and delays the failure to fracture. The addition of diamond facilitates the elimination of thermal cracks, but the porous defects remain in 6061 aluminum alloys. The lower scanning speed extends the contact duration between the laser spot and the processed material, leading to the graphitization of the added diamond and the partial evaporation of the Al matrix. Thus, the internal defects exist, exhibiting the low densification of the composite (relative density 97%). The addition of diamond significantly increases the tensile strength of the LPBF formed diamond/6061 aluminum matrix composites, and the ultimate tensile strength reaches the maximum value of 244.2 MPa, the yield strength is 211.6 MPa, and the elongation is 2.1%, respectively, when the laser power is 350 W and the scanning speed is 800 mm·s−1.
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图 1 3%金刚石/6061铝基复合材料粉末形貌
Figure 1. Morphology of the 3%diamond/6061 aluminum matrix mixture powders
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图 2 不同扫描速度下LPBF成形3%金刚石/6061铝基复合材料相对密度随激光功率变化曲线
Figure 2. Relative density of the 3%diamond/6061 aluminum matrix composites formed by LPBF with the different laser powers at the different scanning speeds
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图 3 激光功率350 W、扫描速度800 mm·s−1条件下6061铝合金（a）和3%金刚石/6061铝基复合材料（b）显微组织
Figure 3. Microstructure of the 6061 aluminum alloys (a) and the 3%diamond/6061 aluminum matrix composites (b) under the laser power of 350 W and scanning speed of 800 mm·s−1
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图 4 3%金刚石/6061铝基复合材料能谱面扫结果
Figure 4. EDS surface scan of the 3%diamond/6061 aluminum matrix composites
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图 5 3%金刚石/6061铝基复合材料能谱点扫位置
Figure 5. EDS spot scan position of the 3%diamond/6061 aluminum matrix composites
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图 6 LPBF成形6061铝合金及3%金刚石/6061铝基复合材料X射线衍射图
Figure 6. XRD patterns of the 6061 aluminum alloys and 3%diamond/6061 aluminum matrix composites formed by LPBF
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图 7 不同成形工艺拉伸曲线:（a）6061铝合金；（b）3%金刚石/6061铝基复合材料
Figure 7. Tensile curves for the different forming processes: (a) 6061 aluminum alloys; (b) 3%diamond/6061 aluminum matrix composites
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图 8 6061铝合金和3%金刚石/6061铝基复合材料的极限抗拉强度和能量密度的关系
Figure 8. Relationship between the ultimate tensile strength and energy density of the 6061 aluminum alloys and the 3%diamond/6061 aluminum matrix composites
表 1 6061粉末化学成分（质量分数）
Table 1 Chemical composition of the 6061 powders
% Si Fe Cu Mn Mg Zn Cr Ti Al 0.4500 0.0560 0.2200 0.0018 0.9500 0.0046 0.1900 0.0012 余量 
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表 2 激光粉末床熔融成形工艺参数
Table 2 Process parameters of laser powder bed fusions
编号 激光功率，
P / W扫描速度，
v / (mm·s−1)能量密度，
EDV / (J·mm−3)1 250 800 148.81 2 250 1000 119.05 3 250 1200 99.21 4 300 800 178.57 5 300 1000 142.86 6 300 1200 119.05 7 350 800 208.33 8 350 1000 166.67 9 350 1200 138.89
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表 3 3%金刚石/6061铝基复合材料能谱点扫结果
Table 3 EDS data of the 3%diamond/6061 aluminum matrix composites
位置 点1 点2 点3 点4 质量分数 / % 原子数分数 / % 质量分数 / % 原子数分数 / % 质量分数 / % 原子数分数 / % 质量分数 / % 原子数分数 / % Al 58.3 38.9 95.5 93.0 76.9 60.7 90.1 81.4 C 40.3 60.3 2.5 5.5 21.7 38.5 8.7 17.6 Si 0.5 0.3 0.6 0.6 0.4 0.3 0.5 0.4 Cu 0.4 0.1 0.5 0.2 0.2 0.1 0.1 0.3 Mg 0.4 0.3 0.6 0.6 0.4 0.3 0.4 0.4 Fe 0.1 0.1 0.3 0.1 0.3 0.1 0.2 0.1
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