【作者】 刘峰；

【导师】 杜双明；

【作者基本信息】 西安科技大学 ， 材料学， 2010， 硕士

【摘要】 镁合金较低的强度和耐磨性限制了其在某些工程中的应用,利用碳化硅颗粒增强镁合金可以明显提高镁合金的拉伸性能和摩擦磨损行为。由于碳化硅与镁在结构和性能上存在较大的差异以及机械搅拌装置的不完善,难以实现增强体与基体在液态或半固态下的充分融合,致使碳化硅颗粒增强镁基复合材料的组织不够均匀致密,性能与工程需要还存在一定差距。本文自行设计制造了机械搅拌复合炉,该实验设备主要包括加热系统、搅拌系统和真空系统,其主要性能参数为:有效工作区尺寸f80mm×120mm,搅拌容器的尺寸f70mm×80mm,功率1kW,最高温度900℃,搅拌速率0～2500r/min,极限真空度0.1Pa。以AZ91D镁合金为基体,平均颗粒尺寸10μm的SiC颗粒为增强相,采用机械搅拌复合炉制备了SiC_p/AZ91D复合材料,研究了搅拌温度、搅拌时间、搅拌速度等工艺参数对复合材料显微组织的影响,并在室温下对复合材料试样进行了拉伸试验和摩擦磨损实验,利用金相显微镜(OM)和扫描电镜(SEM)分别分析了复合材料的显微组织、断口形貌和磨痕形貌。结果表明:在本实验条件下,580℃,1500r/min,搅拌30min时,SiC颗粒在基体中分布相对均匀,并且与AZ91D基体结合较好;在580℃、搅拌时间30min的条件下,随着搅拌速度的增加,SiC颗粒的分布呈现出团聚-部分团聚-相对均匀变化规律,当搅拌速度为1500r/min时,SiC颗粒分布相对均匀;当搅拌速度超过1500r/min后,随着搅拌速度的增加,SiC颗粒分布呈现不均匀化,并出现了气孔。当温度为580℃,搅拌速度1500r/min时,随着搅拌时间的增加,SiC颗粒的分布逐渐趋于相对均匀化,但当搅拌40min时,SiC颗粒分布呈现不均匀化,基体中气孔明显增加。在10vol%,15vol%,20vol%的复合材料中,随着SiC含量的增加,SiC呈现出相对均匀分布-微小聚集团分布-链状分布的规律;复合材料的断裂强度和相对延伸率呈现出下降的趋势。10vol%复合材料的断裂强度为156.2MPa,相对伸长率为4.4%,拉伸曲线没有明显的屈服点,断口为韧-脆混合断口。对于10vol%,15vol%,20vol%复合材料,其平均摩擦系数随着体积分数的增加呈单调增大趋势,磨损量也呈现出单调增大的趋势。与AZ91D相比,10vol%、15vol%、20vol%复合材料的平均摩擦系数分别提高了10.3%、15.7%和31.7%;10vol%、15vol%复合材料的耐磨性分别提高了19.6%,5.5%,但20vol%复合材料的耐磨性略低于AZ91D。10vol%复合材料存在黏着磨损和磨粒磨损两种磨损机制,而15vol%、20vol%的复合材料的磨损过程则以磨粒磨损为主。更多还原

【Abstract】 The application of magnesium alloy was limited, because of lower strength and wear resistance. The tensile properties and the friction and wear behavior of magnesium alloy was improved by introducing SiC particle into magnesium alloys. But there is difference in the performance and structure of the SiC and magnesium alloy, and mechanical agitation device was imperfect, it was difficult to achieve the full mixture of reinforcement and matrix in liquid or semi-solid, and the microstructure of SiC reinforced magnesium composites was not uniform and compact, it will lead to the gap between performance and project needs.In this paper, mechanical stirring compound furnace was designed and manufactured, there were mainly heating system, stirring system and vacuum system in the experimental equipment, and the main performance parameters were the effective heating zone size (f80mm×120mm), the size of stirring vessel(f70mm×80mm), the maximum temperature (900℃), power(1kW), stirring speed(0 ~ 2500r/min) and limited vacuum(0.1Pa)SiC_p/AZ91D composite materials was prepared by mechanical stirring method. The stirring temperature, stirring time and stirring speed were discussed, the tensile and wear properties of composite materials were tested at room temperature. The microstructure of composite materials, the fracture morphology and the morphology of wear defect were analyzed by optical microscopy (OM) and scanning electron microscopy (SEM).The results indicated that: in this experimental conditions, at 580℃, stirring 30min speed 1500r/min, SiC particles relatively dispersed uniformly, and were better to link up with the AZ91D matrix; at580℃, stirring30min, with the stirring speed increased, the distribution of SiC particles showed the variation of reunion - part of the reunion - a relatively uniform, when the stirring speed was up to 1500r/min, SiC particles relatively distributed uniformly, the speed exceed 1500 r/min, with the stirring speed increased, the distribution of SiC particles showed non-uniform, and the pore appeared; at 580℃, stirring speed 1500r/min, with the increase of stirring time, the distribution of SiC showed more and more relative uniformity, but more than 40min, SiC particle distributed unevenly, and there were a large number of pores.In 10vol%, 15vol%, 20vol% composite materials, with the content of SiC increased, the distribution of SiC showed the changes of relatively uniform - small group distribution - the chain distribution, and the trend of the fracture strength and relative elongation decreased. The fracture strength of 10vol% composite material was 156.2MPa, and the relative extension rate was 4.4%. The tensile curve of composites had no obvious yield point, the tensile fracture was mixture of cleavage and touph dimple.In 10vol%, 15vol%, 20vol% composites, with increasing volume fraction monotonously increased, the average coefficient of friction and the wear volume appeared monotonous increasing trend. Compared with AZ91D, the average friction coefficient of 10vol%, 15vol%, 20vol% composite materials respectively increased 10.3%, 15.7% and 31.7%, the abrasion resistance of 10vol%, 15vol% composite increased 19.6% and 5.5%, and the abrasion resistance of 20vol% was slightly less than AZ91D. The wear mechanism of 10vol% composites included two kinds of adhesive and abrasive wear, and the abrasive wear accounted for the main part in 15vol%, 20vol% composites.更多还原