【作者】 王青；

【导师】 李工；

【作者基本信息】 燕山大学 ， 材料学， 2008， 硕士

【摘要】 本文利用真空氩弧熔炼炉制备出Cu₈₂Ti₁₈、Ni₂₀Sn₈₀、Cu₉₅Sn₅合金锭,采用熔融玻璃循环过热法对合金Cu₈₂Ti₁₈、Ni₂₀Sn₈₀、Cu₉₅Sn₅以及大体积合金Cu₉₅Sn₅进行反复熔融净化,改变样品体积、保温时间、过热温度、循环次数等实验参数研究对其过冷度的影响。通过X-ray衍射仪、金相显微镜、维氏显微硬度计等仪器研究了经助熔剂净化后合金的结构、凝固组织和显微硬度变化。X-ray衍射分析表明,合金的衍射峰强度随循环次数的增加而降低,且同样净化条件下小体积合金的衍射峰强度要比大体积合金的衍射峰强度要低,表明大体积合金难以利用玻璃净化法获得非晶态。元素Ti在高温下与助熔剂B₂O₃进行反应,因此不宜用B₂O₃对Cu-Ti合金进行净化处理;经过助熔剂净化后,小体积合金Ni₂₀Sn₈₀的凝固组织成分均匀,晶粒明显细化;小体积合金Cu₉₅Sn₅的过冷度随循环次数的增加有变大的趋势,其凝固组织由树枝晶变为等轴晶,且晶粒细化,其显微硬度随循环次数的增加而降低;大体积合金Cu₉₅Sn₅的过冷度随循环次数的增加有变大的趋势,由于其内外冷却速率的差异,样品的凝固组织分布不均匀,其内部区域的显微硬度随冷却速率的增加而降低,而样品表面发生硬化。更多还原

【Abstract】 Cu₈₂Ti₁₈, Ni₂₀Sn₈₀ and Cu₉₅Sn₅ ingots were prepared by remelting and casting in an argon-arc furnace, then solidified by glass fluxing, the effects of sample volume, heat preservation time, superheat temperature and circular times on the undercooling of the sample were researched in the glass fluxing experiment. Their solidification morphology, structural evolution and microhardness were investigated by X-ray diffraction, Metallographic microscope and the Vicker’s sclerometerm.X-ray diffraction analysis showed that the diffraction intensity of the sample decreased with the increase of the circular times, and the diffraction intensity of small size alloy was lower than large size alloy in the same glass fluxing condition.Research results exhibited that element Ti can occur chemical reaction with the fluxing B₂O₃ on high temperature,so Cu-Ti alloy cannot be purified by the fluxing B₂O₃. After glass fluxing, the solidification morphology of Ni₂₀Sn₈₀ alloy distributed equably, and grain refine behavior was obvious. The undercooling of small size alloy Cu₉₅Sn₅ became higher with the increase of the circular times, the solidification morphology transformed from coarse dendrites to equiaxed grains and grains refined, microhardness reduced with the increase of circular times. The undercooling of bulk alloy Cu₉₅Sn₅ became higher with the increase of the circular times. Due to the cooling rate difference of the external and internal, their solidification morphology distributed asymmetric, the internal microhardness lowered with the increase of the cooling rate, while the external of the sample occurred the surface hardening behavior.更多还原