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首页> 外文学位 >Influence of metallurgical parameters on the mechanical properties and quality indices of Al-Si-Cu-Mg and Al-Si-Mg casting alloys.
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Influence of metallurgical parameters on the mechanical properties and quality indices of Al-Si-Cu-Mg and Al-Si-Mg casting alloys.

机译：冶金参数对Al-Si-Cu-Mg和Al-Si-Mg铸造合金的力学性能和质量指标的影响。

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摘要

The current study was carried out with a view to investigating the influence of a number of metallurgical parameters on the tensile properties and quality indices of two high strength Al-9%Si casting alloys, namely, 354 and 359, containing 1.8%Cu-0.5%Mg and 0.5%Mg, respectively.;An increase in the solutionizing temperature improves the strength and quality of the castings compared to the as-cast condition. In accordance with these findings, maximum safe solutionizing temperatures of 520°C and 537°C are respectively recommended for heat treating 354 and 359-type castings to produce superior strength and optimum quality. Solution treatment at these temperatures is observed to bring about a number of improvements in the microstructure by which the strength and the quality are thereby enhanced. Solution treatment at temperatures above 525°C results in the incipient melting of the Al 2Cu phases in the 354 alloys and the formation of high levels of shrinkage porosity after quenching. As a consequence of the incipient melting, silicon particles in the microstructure exhibit a polygonal morphology in areas where the melting of the Al2Cu phase has occurred.;An increase in the solution heat treatment time further enhances the tensile properties and the quality index values of the 354 and 359 alloys. Twelve hours was judged as the optimum solution heat treatment time for these castings. The solution time required to obtain a specific level of tensile properties and quality index in the unmodified 354 and 359 alloys may be shortened by modifying these alloys with strontium. However, the beneficial effect of Sr-addition on the response of the 354 and 359 alloys to solution treatment diminishes as the solution heat treatment time is increased.;Aging at 155°C is observed to produce the highest strength and optimum quality in both 354 and 359-type castings compared to aging at higher temperatures. The peak-strength observed for 354 and 359 alloys may be attained after shorter aging times on condition that the aging temperature is increased. The aging times required for reaching peak-strength in 354 alloys are 72 hours, 40 hours, 8 hours, 1 hour, and 15 minutes at aging temperatures of 155°C, 170°C, 195°C, 220°C, and 245°C, respectively, while the aging times required for reaching peak-strength in 359 alloys are 32 hours, 24 hours, 1 hour, 30 minutes, and 10 minutes, respectively, at these same aging temperatures.;An analysis of the results shows that the addition of iron has deleterious effects on both the strength and the quality of these alloys. These effects are related to the size and morphology of the iron-containing phases, specifically, beta-Al 5FeSi and pi-Al8Mg3FeSi6 present in the alloys. The addition of copper to 359-type alloys plays a significant role in improving the alloy strength; this improvement occurs, however, at the expense of ductility and therefore only a slight effect on the quality index is noted. The addition of up to 0.6% magnesium to 359-type alloys considerably improves their strength without affecting the quality. Increasing the Mg-level beyond 0.6% results in a slight increase in the alloy strength with a noticeable reduction in ductility and quality index due to the formation of a large volume fraction of the pi-Al8Mg3FeSi6 phase.;Aging at higher temperatures is accompanied by a reduction in the tensile properties and quality index value. On the other hand, it also introduces the possibility of achieving significant economic gains by minimizing the time and cost of the treatment. Aging treatment at the lower temperature of 155°C produces fine and dense precipitates having smaller inter-particle spacings, while at a higher aging temperature such as 245°C, the precipitates are coarser in size, less dense, and more widely dispersed in the matrix. The 354 alloys were observed to display higher strength levels when compared to the 359 alloys for all aging treatments. This high strength, however, was obtained at the expense of ductility, resulting in slight variations in the quality index values of the 354 castings. (Abstract shortened by UMI.)
机译：进行当前研究的目的是调查许多冶金参数对两种高强度Al-9％Si铸造合金（含1.8％Cu-0.5的354和359）的拉伸性能和质量指标的影响。分别为％Mg和0.5％Mg 。；与铸态相比，固溶温度的提高提高了铸件的强度和质量。根据这些发现，建议对354和359型铸件进行热处理时，最高安全固溶温度分别建议为520°C和537°C，以产生出众的强度和最佳质量。观察到在这些温度下的固溶处理在微观结构上带来了许多改进，从而提高了强度和质量。在高于525°C的温度下进行固溶处理会导致354种合金中的Al 2Cu相开始熔化，并在淬火后形成高水平的收缩孔隙率。由于开始熔化，微观结构中的硅颗粒在发生Al2Cu相熔化的区域呈现多边形形态。;固溶热处理时间的增加进一步提高了Al2Cu相的拉伸性能和质量指标值354和359合金。对于这些铸件，十二小时被认为是最佳的固溶热处理时间。在未改性的354和359合金中获得特定水平的拉伸性能和质量指标所需的固溶时间可以通过用锶改性这些合金来缩短。然而，随着固溶热处理时间的增加，添加锶对354和359合金固溶处理响应的有利影响逐渐减弱。观察到在155°C时效可在354中产生最高的强度和最佳的质量与359型铸件相比，在较高温度下会时效。在时效温度升高的条件下，经过更短的时效时间后，可以获得354和359合金的峰值强度。在155°C，170°C，195°C，220°C和245的时效温度下，在354种合金中达到峰值强度所需的时效时间分别为72小时，40小时，8小时，1小时和15分钟。在相同的时效温度下，359种合金达到峰值强度所需的时效时间分别为32小时，24小时，1小时，30分钟和10分钟。铁的添加对这些合金的强度和质量都有不利影响。这些效应与合金中存在的含铁相的大小和形态有关，特别是β-Al5FeSi和pi-Al8Mg3FeSi6。在359型合金中添加铜对于提高合金强度起着重要作用。但是，这种改进是以延展性为代价的，因此，对质量指标的影响很小。在359型合金中添加多达0.6％的镁，可在不影响质量的前提下大大提高其强度。由于形成大量的pi-Al8Mg3FeSi6相，使Mg含量超过0.6％会导致合金强度略有增加，同时延展性和质量指标显着降低。降低拉伸性能和质量指标值。另一方面，它也引入了通过最小化治疗时间和成本来获得显着经济收益的可能性。在155°C的较低温度下进行时效处理会产生细小而致密的沉淀，颗粒间的间距较小，而在较高的时效温度（如245°C）下，沉淀的尺寸更大，密度较小，并且在颗粒中的分布更广。矩阵。与所有时效处理的359合金相比，观察到354合金显示出更高的强度水平。然而，以延展性为代价获得了这种高强度，导致354个铸件的质量指标值略有变化。 （摘要由UMI缩短。）

著录项

  • 作者

    Ammar, Hany.;

  • 作者单位

    Universite du Quebec a Chicoutimi (Canada).;

  • 授予单位 Universite du Quebec a Chicoutimi (Canada).;
  • 学科 Engineering Metallurgy.
  • 学位 Ph.D.
  • 年度 2010
  • 页码 269 p.
  • 总页数 269
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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