Si、Cu元素与热处理对Al-30Zn高锌铝合金组织及性能的影响

发布时间：2018-01-08 15:36

本文关键词：Si、Cu元素与热处理对Al-30Zn高锌铝合金组织及性能的影响　出处：《郑州大学》2017年硕士论文　论文类型：学位论文

【摘要】：铸造锌铝合金的突出优点是,价格便宜成本低、硬度强度高、尺寸稳定性较好,可自然时效强化,无需热处理即可直接替代传统耐磨材料(Sn基或Pb基巴氏合金、锡青铜合金和球墨铸铁等),制造轴套、轴承等耐磨件。同时,锌铝合金密度较低、热导率和电导率适中、极限抗拉强度高、承载性好、无磁性以及碰撞时不产生火花,以及一些其它的独特性能。但是,锌铝合金易晶间腐蚀,加快腐蚀磨损及老化失效,高温时其力学性能急剧下降、摩擦系数增大、热稳定性变差等,长期以来极大的限制了其广泛应用。为了改善锌铝合金的这些缺陷,获得耐蚀性、高温耐磨性均优异的合金,本文以Al-30Zn合金为基础合金,添加合金元素Si、Cu,结合硬度试验、室温拉伸试验、热稳定性试验、冲击韧性试验、摩擦磨损试验、电化学试验及浸泡试验,系统研究了Si、Cu元素对Al-30Zn高锌铝合金显微组织、机械性能、热稳定性能、耐磨性能和耐腐蚀性能的影响;探讨了均匀化热处理对Al-30Zn-3Si-2Cu高锌铝合金显微组织、力学性能及耐磨性能的影响。得到主要结论如下:Al-30Zn高锌铝合金铸态微观组织,由初生富铝α树枝晶、共析(α+η)相组成。添加适量Si元素,组织中出现硬质共晶Si相,当超过3.0wt.%Si时,共晶Si相变粗变大,产生微观偏析,同时析出块状初晶硅相,且随着Si含量增加,其数量变多,形态恶化。随着Si元素含量的增加(Si含量小于3.0wt.%),显微硬度随之提高,高温强度得到较大改善,高温下尺寸更加稳定,磨损量减小,合金耐磨性能提高,但会降低合金韧塑性。同时,随着Si含量的增加,Al-30Zn高锌铝合金自腐蚀电位将正移,腐蚀倾向虽减小,但会增加腐蚀微电池数量,增大腐蚀速率,加重晶间腐蚀,电化学性能呈降低的趋势。Al-30Zn-3Si高锌铝合金添加适量Cu元素,组织中析出富铜θ(CuAl2)相,弥散分布在晶界及晶界附近,明显细化Al-30Zn-3Si合金的晶粒,增加组织的均匀化程度,当超过2.0wt.%Cu时,富铜θ(CuAl2)相增多,颗粒尺寸变大,已无法弥散分布,开始呈网状分布。随着Cu元素含量的增加(Cu含量小于2.0wt.%),合金的显微硬度、抗拉强度、耐磨性能均获得较大提升,但会削弱合金韧塑性;添加适量Cu元素,使自腐蚀电位正移,降低腐蚀倾向,同时降低腐蚀速率,改善Al-30Zn-3Si合金耐蚀性能,但随着Cu元素含量的增加,析出的θ相连成网状,使基体中各相的电极电位差变大,从而增加腐蚀微电池数量,促进晶间腐蚀。铸态Al-30Zn-3Si-2Cu高锌铝合金,韧塑性比较低,经400℃/10h均匀化退火后,裂纹、缩孔、位错堆积、晶内成分偏析及枝晶偏析等微观缺陷明显减少,共析组织呈细片状,共晶Si相、θ相发生断裂、球化,均匀弥散分布在晶界及晶界附近处,低熔点共晶物几乎消失,其强度硬度较铸态时稍低,但塑性及冲击韧性得到了较大的提高,伸长率(5.59%)约是铸态(3.35%)的1.67倍,且合金的耐磨性也得到了进一步的提,综合性能较好。
[Abstract]:The outstanding advantages of casting zinc Aluminum Alloy is cheap, low cost, high hardness and strength, good dimensional stability, natural aging strengthening, direct replacement of traditional wear resistant materials without heat treatment (Sn base or Pb base bearing alloy, tin bronze alloy and nodular cast iron), making sleeve, bearing wear parts. At the same time, zinc Aluminum Alloy low density, thermal conductivity and electrical conductivity is moderate, high tensile strength, good bearing capability, no spark is generated without magnetic, collision, and other unique properties. However, zinc Aluminum Alloy easily intergranular corrosion, wear and corrosion and high temperature aging, the mechanical properties of sharp fall, the friction coefficient is increased, the thermal stability becomes poor, long time greatly limit its application. In order to improve the defects of zinc Aluminum Alloy, obtain excellent corrosion resistance, high temperature wear resistance alloy, on the basis of Al-30Zn alloy Alloy, alloying elements Si, Cu, and hardness test, tensile test and thermal stability test, impact toughness test, friction wear test, electrochemical test and immersion test system of Si, Cu elements on the properties of Al-30Zn high zinc Aluminum Alloy microstructure, mechanical, thermal stability, impact resistance and corrosion resistance performance; discusses the homogenization heat treatment of Al-30Zn-3Si-2Cu high zinc Aluminum Alloy microstructure effect, mechanical properties and wear resistance performance. The main conclusions are as follows: as cast microstructure of high zinc Aluminum Alloy Al-30Zn, composed of primary aluminum rich alpha dendrite, eutectoid (alpha + ETA) phase. The addition of Si element, phase the rigid Si eutectic organization, when more than 3.0wt.%Si, the coarse eutectic Si phase change, micro segregation and precipitation at the same time the bulk primary silicon phase, and with the increase of Si content, the number, morphology deteriorated. With the increase of Si content ( The content of Si is less than 3.0wt.%), the micro hardness increases, high temperature strength has been greatly improved, the size is more stable under high temperature, wear rate decreases, improve the wear resistance of the alloy, but lower alloy plasticity. At the same time, with the increase of Si content, high zinc Aluminum Alloy Al-30Zn corrosion potential positive shift, although the corrosion tendency reduce, but will increase the number of micro corrosion cell, increase corrosion rate increase, intergranular corrosion, electrochemical properties of.Al-30Zn-3Si showed a trend of high zinc Aluminum Alloy reduced adding Cu element, in precipitation of Cu rich phase dispersion, theta (CuAl2) distributed on the grain boundary and grain refinement of Al-30Zn-3Si alloy, and increase the uniform the degree of organization, when more than 2.0wt.%Cu, copper rich theta (CuAl2) phase increased, particle size change, has not dispersed, a mesh distribution. With the increase of Cu content (Cu content less than 2.0wt.%), the microstructure of alloy The hardness, tensile strength and wear resistance are greatly improved, but will weaken the alloy plasticity; adding Cu element, the self corrosion potential, reduce corrosion, and the corrosion rate decreased, improve the corrosion resistance of Al-30Zn-3Si alloy, but with the increase of Cu content, the precipitation of theta phase into the net, the matrix electrode potential of each phase difference, thus increasing the number of micro corrosion cell, promote intergranular corrosion. Al-30Zn-3Si-2Cu cast high zinc Aluminum Alloy, toughness is relatively low, with 400 DEG /10h after homogenizing annealing, crack, shrinkage, dislocation accumulation, intragranular segregation and dendrite segregation microstructure the defect was significantly reduced, eutectoid fine flake, eutectic Si phase, theta phase fracture, spherical, uniform distribution near the grain boundary and grain boundary, the eutectic almost disappeared, the strength of the as cast hardness is slightly lower, but the plasticity and impact toughness is gained. The elongation rate (5.59%) is about 1.67 times that of the cast state (3.35%), and the wear resistance of the alloy has been further raised, and the comprehensive performance is better.

【学位授予单位】：郑州大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG146.21;TG166.3

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