【作者】 过超群；

【导师】 王尔德；

【作者基本信息】 哈尔滨工业大学 ， 材料加工工程， 2010， 硕士

【摘要】 本文针对Cu-Cr-Zr合金和固相不互溶高Cr含量的Cu-(30~50%)Cr材料的热挤压工艺及轧制工艺对组织和性能影响进行了实验研究。研究挤压工艺、退火工艺和时效工艺对Cu-Cr-Zr合金组织性能的影响;研究挤压轧制工艺、退火工艺和时效工艺对高Cr含量的Cu-(30~50%)Cr材料组织性能的影响。对Cu-Cr-Zr合金采用不同温度下的热挤压后,发现650℃下进行热挤压的合金硬度和电导率都达到了最高,850℃热处理1.5h后硬度和电导率都有很大降低,经450℃时效处理3.5h后硬度和电导率都提高很多,其中最佳工艺为800℃热挤压后在450℃下时效处理3.5h,800℃温度下挤压后材料的晶粒的得到细化,Cr相析出量较少,致使材料性能提高,经时效处理后富Cr相进一步大量析出,致使材料的硬度和电导率再次提高。高Cr含量的Cu-Cr材料一般采用粉末冶金的方法制备,采用熔铸工艺制备的Cu-(30~50%)Cr材料Cr相尺寸比粉末冶金方法的更粗大。由于Cu-Cr固相基本不互溶,Cu-Cr相界面结合很弱,故该材料塑性很差,塑性变形极易开裂,为此研究高Cr含量的Cu-Cr材料的热挤压和热轧制变形对组织性能的影响,不仅具有学术价值,而且具有重大的现实生产意义。对Cr含量为30%、40%、50%的Cu-Cr材料进行热挤压和热轧制,发现材料加热到850℃进行挤压后,材料的硬度和电导率都有较大提高,退火处理后硬度降低电导率基本不变,时效处理后材料硬度和电导率基本没有改变。Cr含量越高的材料硬度越高但电导率越低。轧制后的材料硬度和电导率都有所降低并且沿轧制方向电导率降低更多。经热挤压的铜铬材料,Cr相沿挤压方向被拉长,变形量较大,铜基体晶粒也得到细化,材料的硬度提高,虽然Cr相与铜基体接触面增加,但铜基体变得更加连续,导电性能得到提高;热轧后材料中的Cr相变化不大,铜基体的晶粒长大致使硬度稍有降低,Cr相与铜基体接触面的增加致使电导率略微降低。而退火处理导致硬度的降低是因为铜基体晶粒长大所致,时效强化对此类材料影响甚微。更多还原

【Abstract】 The extruding and rolling processes of the Cu-Cr-Zr alloys and the high Cr content Cu-(30~50wt.%) Cr alloy were investigated. Research on the effect of extruding, annealing and aging treatment on microstructures and mechanical properties of the Cu-Cr-Zr alloys and the influence of extruding, rolling, annealing and aging on microstructures and mechanical properties of the high Cr content Cu-(30~50wt.%) Cr alloy have been studied.The results show that the hardness and electrical conductivity of Cu-Cr-Zr alloys were highly dependent on the extruding parameters. The maximum hardness and electrical conductivity was obtained at an extrusion temperature of 650℃, both hardness and electrical conductivity of the extruded alloys had a remarkable decrease when annealed at 850℃for 1.5h. However, that has a great increase when aged at 450℃for 3.5h. It is also observed that the good combination of hardness and the electrical conductivity could be achieved at an extrusion temperature of 800℃and subsequent annealing temperature of 450℃for 3.5h. Because grains of the as-extruded samples were significantly refined after hot extruded at 800℃, and slight Cr phase precipitation can be observed, which resulted in the enhancement of properties. Further precipitation of fine Cr-rich phase particles in the subsequent aging process reinforced both properties.It is generally accepted that the high Cr content of Cu-Cr materials are generally prepared by powder metallurgy. Size of Cr phase particles of Cu-(30~50 wt.%) Cr prepared by casting is much coarser than that prepared by powder metallurgy. Because the Cu matrix and Cr phase are immiscible, the Cu-Cr phase bonding is weak. Thus, the plasticity of the material is poor, which lead it easily cracked in plastic deformation. The study aims to investigate the effect of hot extruding and rolling on microstructures and mechanical properties of these materials. The academic value and important practical production sense are obvious. Hot rolling and extruding were performed on Cu-Cr materials with the Cr content of 30%, 40$ and 50%. The result shows that the hardness and electrical conductivity improved significantly after extruded at 850℃, but the change of the properties was not obvious after aging. After annealing, decrease in micro-hardness presented but the electrical conductivity was constant. The higher Cr content leads higher hardness but lower electrical conductivity. The hardness and electrical conductivity of Cu-(30~50 wt.%) Cr material was reduced after rolling, especially along the rolling direction. The Cr phase was elongated along the extrusion direction. As a result of large extrusion ratio, the grain size of Copper matrix has been refined, the hardness increased. Although the contacting area between Cr phase and copper increased, the copper matrix became more continuous, promoting the improvement of electrical conductivity. The change of Cr phase in the material is not obvious after hot rolling, the copper grain growth resulted in slightly lowered hardness. Increasing of the area of Cr phase and copper contacting resulted in slightly lowered electrical conductivity. The annealing treatment resulted in decreased hardness because of the grain growth in Cu matrix. The effect of age-hardening on properties of such materials is minimal.更多还原