纯镁等通道变形组织与性能_金属材料工程.rar

摘要：镁及其合金是迄今工程应用中最轻的结构材料之一，纯镁的密度为1.74g/cm3，具有高的比强度（强度/密度），可铸性好，导热导电能力强等，但是纯镁的强度不高，耐腐蚀性较低。本文以纯镁为研究对象，通过对铸态纯镁、退火态纯镁及其相应的等通道变形（ECAP），研究ECAP变形对纯镁的显微组织和显微硬度的影响。本文采用12mm/min和6mm/min速度的ECAP变形对纯镁进行1道次处理，实验结果表明，与铸态纯镁相比，变形后的纯镁得到了显著的细化，显微硬度也得到了提高。

　　　对铸态纯镁试样在保护气氛下（氩气）进行退火处理，退火后纯镁经过ECAP后的细化效果更加明显，退火态纯镁的粗大晶粒被破碎成细小的晶粒，晶粒尺寸从~400μm减小到~100μm。经过对变形前后显微硬度的测量，ECAP变形纯镁的显微硬度也要高于铸态纯镁的硬度。

　　　在无保护气氛条件下，对铸态纯镁进行不同温度下的退火处理，铸态晶粒尺寸~4mm，500℃退火后的晶粒尺寸~1.5mm，550℃退火后晶粒尺寸~0.2mm，不难看出，退火温度越高，退火后晶粒细化越明显。与无保护气氛下退火纯镁相比，在500℃保护气氛下退火时，晶粒尺寸就已经细化到~0.4mm，保护气氛退火细化效果更明显。

关键词：纯镁；等通道变形；退火；组织；性能

Abstract:Magnesium and its alloy is one of the lightest structural materials in the engineering applications so far. The density of pure magnesium is 1.74g/cm3, it has excellent performances, such as the high strength/weight ratio, castability and electrical conductivity. In this paper, the pure magnesium as the research object was used, the microhardness and microstructure of the as-cast pure magnesium, heat treatment of as-cast pure magnesium and the corresponding pure magnesium processed by ECAP were investigated. The experiment processed the pure magnesium by 1 pass in the speed of 12mm/min and 6mm/min, the results of the experiment show that, coarse grains in cast pure magnesium was broken into smaller grains, and its microhardness was improved.

　　　Annealing the as-cast pure magnesium in protective atmosphere, the annealed pure magnesium processed by ECAP shows better refined ability. After annealing, the coarse grains were broken into smaller grains, the grain size was reduced from the initial ~400 μ m to ~100 μ m after one ECAP pass. By measuring the microhardness of the samples before and after deformation, the pure magnesium after ECAP shows the higher microhardness.

　　　In unprotective atmosphere condition , the pure magnesium was annealed in different temperatures, the grain size of the pure magnesium was ~4mm, the grain size affter annealing at 500℃ was ~1.5mm, the grain size after annealing at 550℃ was ~0.2mm.It is obvious to see that the higher temperature, the smaller the grain. Compared with the condition in unprotective atmosphere, annealing at 500℃ in protective atmosphere ,the grain size was ~0.4mm. Annealing in protective atmosphere shows better grain refinement.

Key words: pure magnesium; ECAP; anneal; structure; property.