Characterization Of Interface Structure And Properties Of Diamond/Al Composite

In order to improve the reliability of diamond/Al composite materials,the properties of composite materials with different interface structures were investigated.In this paper,diamond/aluminum composites were prepared by vacuum pressure infiltration method using different particle sizes,different coatings of diamond and pure aluminum as raw materials.Among them,five particle sizes are selected from 100?m to 240?m.The diamond surface coating selection is uncoated,50 nm W coating,50 nm WC coating and 100 nm WC coating,wherein W-coated diamond is prepared by magnetron sputtering,and different thickness WC-coated diamond is obtained by using different thicknesses of W-coated diamond.Prepared by high temperature treatment.When the uncoated and 50 nm W coated diamond particles were increased from 100?m to 240?m,the thermal conductivity of the composites increased by22.5% and 21.2%,and the strength and thermal expansion performance also increased.Therefore,240?m is determined as the optimal particle size of the diamond particles,and this rule does not change with the presence or absence of the coating.Therefore,using different coated 240?m diamond particles as reinforcement,diamond/aluminum composites with different interface structures were obtained.The results showed that the uncoated diamond/Al composites produced Al₄C₃ phase at the interface during the preparation.The observation of fracture morphology revealed that the {100} crystal face of diamond easily reacted with aluminum,and the {111} crystal face was debonded with aluminum..The metal or carbide-coated diamond composites can significantly improve this phenomenon and eliminate the interface selectivity of the aluminum matrix to the diamond reaction.The W and WC coatings reacted with aluminum during the preparation process to produce the intermetallic compound Al5 W.When the coating reaction is complete,exposure of the diamond to the aluminum liquid will result in the formation of an Al₄C₃ phase at the interface,but at this time the Al₄C₃ content is less than that in the uncoated diamond/aluminum composite and the size is smaller.When the coating remains,the generation of Al₄C₃ is completely suppressed,and the size of Al5 W increases.In addition,the amorphous carbon formed by the reaction of WC and Al is also present in the composite material corresponding to the WC coating.This phase structure exists outside the diamond,and the isolated aluminum comes into contact with thediamond,which suppresses the formation of Al₄C₃,and on the other hand,it is weak.The bonding phase reduces the interfacial bonding force of the composite material.Among the four interface composites,the uncoated diamond/Al composites have the highest thermal conductivity of 749W/?m·K?;the 100 nm WC coating diamond/Al composites have the lowest thermal conductivity of 632W/?m·K?.The 50 nm W coating corresponding to the highest strength of the composite material was 312 MPa.The thermal expansion coefficients of the four composites are in the range of 6.8 x 10^-6/K to 7.5 x 10^-6/K.In the reliability experiment,the composite material was placed in a hot and humid environment at 60?.and 90% relative humidity for 60 days.The thermal conductivity of the 100 nm WC coating composite material did not decrease;the uncoated,50 nm W,50 nm WC coating composite material decreased by 8 %,7%,and 6%,due to the gradual reduction of Al₄C₃ content,the three materials reached the lowest thermal conductivity after 40,30 and 20 days respectively.The thermal shocks test was conducted in the temperature range from-65? to150?.After 1000 thermal shocks,the thermal conductivity of the 50 nm W coating composite material decreased by a minimum of 12%,while the thermal conductivity of the composite material without 50 nm WC and 100 nm WC decreased.17%,21%,27%.