| High performance aluminum alloys and aluminum matrix composites with large dimensions find wide applications in the fields of aerospace, automobile, defense and so on. Spray deposition is considered to be one of the most effective technologies to produce such materials. However, the conventional spray deposition process is difficult to prepare rapid solidified preforms with large dimensions. In this dissertation, a novel spray deposition technology, termed as Crucible Movable Spray Deposition Technology, and two sets of equipments were developed to prepare rapidly solidified preforms with large dimensions and meet the demand of a certain "National Tenth Five Year Plan" project, and the spray deposition processing was optimized. On the basis of this, the micro structure evolution and the mechanical properties of the 7075/SiCp composites during densification and heat treatment processing were systematically investigated and their friction and wear properties were also examined in the end. The conclusions were drawn as follows:1. The concept of the novel spray deposition equipment was put forth on the basis of understanding the defects of conventional spray deposition technology in preparing large-sized rapidly solidified preforms and the equipments for the fabrication of tubular preforms and billets were successfully designed. The principle of the equipments was analyzed and the optimized processing parameters were determined. Tubular aluminum alloy preforms with the dimension of (?)800×1400×300mm, aluminum alloy rings with the dimension of (?)3300×2900×200mm and billets with the diameter up to 01000mm, and 7075/15%SiCp composite billets with the dimension of (?)630×800mm were fabricated. The as-prepared preforms were charactersistic of excellent microstructure homogeneity combined with fine grain and uniform distribution of SiC particles.2. The densification processing of the spray-deposited composite preforms was investigated. The heat simulation method was chosen to examine the formability of the 7075/SiCp composite preforms under compression at elevated temperature. The microstructure evolution of the samples during compression was also investigated. The experimental results showed that the preforms exhibited good formability at 420℃ and with the compression strain rate less than 0.01s"1 when lubricatd.The extrusion formability of the 7075/SiCp preforms, the distribution and theflowing characteristics of SiC particles during extrusion and the mechanical properties of the as-extruded materials were studied with a YJ32-315 press and a 1250T extrusion press. The results showed that the preforms possessed good extrusion formability, and densification of the preforms was the primary effect of extrusion. The relative density was up to 97.5% in this study and the porosity and the interface between the deposited layers disappeared after extrusion. The fine and typical spray-deposited microstructures were remained, but the distribution state of the SiC particles was streamline along the extrusion orientation. The mechanical properties of the preforms module pressed were as follows: os=349.4]Vn^ ab=468.2MPa> 5=10.2%. Thick 7075/15%SiCp composite plates with the dimension of 330mmxl25mmx6000mm were successfully extruded in the 12500T extrusion press from billet preforms with the dimension of 063O><8OOmm.The rolling processing of aluminum matrix composites reinforced with SiC particles was investigated. The results showed that the direct rolling processing resulted in poor formability, but the rolling formability of the composite could be effectively improved through extrusion. The rolling formability and the mechanical properties of the as-rolled sheets were controlled by the rolling direction and the processing parameters. Rolling orientation parallel to the extrusion orientation and cross rolling processing at less reduction in pass were beneficial. SiC particles tended to fracture and round-angled. The mechanical properties of the as-rolled 7075/SiCp composite sheet were: as=518.8MPa, ab=584.36MPa, 5=1.41%o3. 7075Al alloy is a typical aging strengthening alloy. Heat treatment processing, microstructure and mechanical properties of the extruded and the rolled 7075/SiCp composites were investigated. The optimum parameters of solution treatment for the 7075/SiCp composite bar was 445°C held for 30min. SiC particles accelerated the aging rate of the composites. Compared with the as-extruded 7075 alloy bars from casting ingots and spray-deposied preforms, the suitable solution temperature and time for the as-extruded 7075/SiCp composite bars were shorter, and the hardness of the bars was higher. However, the peak aging strength and elongation of the bars were lower than those of the spray- deposited 7075 alloy. The properties of the as-extruded 7075/SiCp composite bars were:(1)T6: os=479.1MPa, ab=660.7MPa, 5 = 3.3%;(2)Solutized at 445°C for 30min + aged at 24°C for 120h + aged at 120°C for 15h: as=485.2MPa, ab=663.8MPa, 5=1.2%;The properties of the as-rolled 7075/SiCp composite sheets were:...
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