论文部分内容阅读
采用粉末冶金法制备了名义尺寸为150、300、500 mm的片层石墨(graphite flakes,Gf)增强铝基(50%Gf/Al,体积分数)复合材料,得到密度均接近理论密度的致密复合材料坯锭。片层石墨与铝合金基体结合紧密,界面处无裂纹、孔洞等缺陷。片层石墨的(001)Gf基面与复合材料坯锭的圆周方向(坯锭的xy平面)基本平行,但受粉末冶金工艺的影响,较小片层石墨的(001)Gf基面与坯锭的xy平面略有偏差。随着片层石墨的尺寸增大,偏差逐渐减少。复合材料的强度随着片层石墨尺寸增加逐渐降低。150 mm片层石墨复合材料的弯曲强度为82 MPa,当片层石墨尺寸增至500 mm时,强度降低至39 MPa。片层石墨强度较低,裂纹容易沿片层石墨的层间扩展,随着片层石墨尺寸增大,这一现象更加明显,容易在断口中观察到片层石墨剥离的现象。复合材料xy平面的热导率随片层石墨尺寸增大而增加,最高可达604 W/(m·K),与尺寸较小的片层石墨相比提高63%。300、500 mm片层石墨复合材料的界面换热系数略低于理论值,但150 mm片层石墨复合材料的界面换热系数明显小于理论值。除了片层石墨的尺寸,其形状、分布和内部缺陷等对复合材料的热导率也有一定的影响。
A series of graphite flakes (Gf) reinforced aluminum matrix (50% Gf / Al, volume fraction) composites with nominal sizes of 150, 300 and 500 mm were prepared by powder metallurgy method to obtain compact composites with density close to the theoretical density Material billet. Laminates graphite and aluminum alloy substrate close, no cracks at the interface, holes and other defects. The (001) Gf basal plane of the flake graphite is almost parallel to the circumferential direction of the composite billet (the xy plane of the billet). However, due to the powder metallurgy process, the (001) Gf basal plane and the billet The xy plane of the ingot slightly deviates. As the size of the graphite layer increases, the deviation gradually decreases. The strength of the composites decreases with the increase of the graphite size. The flexural strength of 150 mm lamellar graphite composites was 82 MPa. When the lamellar graphite size increased to 500 mm, the strength was reduced to 39 MPa. Lamellar graphite is low in strength, and the cracks easily spread along the layers of graphite. This phenomenon is more obvious with the increase of the graphite size, which makes it easy to observe the delamination of graphite in the fracture. The thermal conductivity of the composite xy plane increases with the size of the graphite layer, up to 604 W / (m · K), which is 63% higher than that of the smaller size graphite. The interface heat transfer coefficient of 300,500 mm sheet graphite composites is slightly lower than the theoretical value, but the interface heat transfer coefficient of 150 mm sheet graphite composites is obviously less than the theoretical value. In addition to the size of the graphite layer, its shape, distribution and internal defects on the thermal conductivity of the composite materials also have a certain impact.