Tham khảo tài liệu 'asm metals handbook - desk edition (asm_ 1998) episode 10', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Table 5 Physical properties of an Al SiC xxp MMC for electronic applications Property Composite SiC loading Typical aluminum alloys 55 vol 70 vol Coefficient of thermal expansion 10-6 C 10-6 F 22-24 12-13 Thermal conductivity W m K Btu h ft F 160 93 170 99 150-180 87-104 Density g cm3 lb Elastic modulus GPa 106 psi 200 29 270 39 70 10 Spray deposition involves atomizing a melt and rather than allowing the droplets to solidify totally as for metal powder manufacture collecting the semi-solid droplets on a substrate. The process is a hybrid rapid solidification process because the metal experiences a rapid transition through the liquidus to the solidus followed by slow cooling from the solidus to room temperature. This results in a refined grain and precipitation structure with no significant increase in solute solubility. The production of MMC ingot by spray deposition can be accomplished by introducing particulate into the standard spray deposition metal spray leading to codeposition with the atomized metal onto the substrate. Careful control of the atomizing and particulate feeding conditions is required to ensure that a uniform distribution of particulate is produced within a typically 95 to 98 dense aluminum matrix. A number of aluminum alloys containing SiC particulate have been produced by spray deposition. These include aluminum-silicon casting alloys and the 2xxx 6xxx 7xxx and 8xxx aluminum-lithium series wrought alloys. Significant increases in specific modulus have been realized with SiC-reinforced 8090 alloy Table 6 . Products that have been produced by spray deposition include solid and hollow extrusions forgings sheet and remelted pressure die castings. Table 6 Properties of conventionally processed aluminum alloys ingot metallurgy and spray-deposited aluminum MMCs Material Elastic modulus Density g cm3 lb Specific modulus Improvement GPa 106 psi 2014 72 10 0 8090 80 12
