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1、河北工业大学硕士学位论文 i ZAlSiZAlSi7 7MgYMgY 合金合金组织遗传性组织遗传性研究研究 摘摘 要要 与铸件质量相关的许多问题在很大程度上取决于原材料的质量，因为原材料的质量直 接影响铸件的质量，这就是金属基因工程即金属组织遗传要研究和解决的问题。今天，金 属组织遗传现象无论是在理论上或是在实践中都是新的研究课题，它对铸造生产中铸件质 量的改善，综合性能的提高以及制订合理的工艺措施都具有重要的意义。 论文以 ZAlSi7MgY 铝合金为研究对象，通过制定不同的工艺对原料组织遗传现象进行 了研究，并提出利用组织遗传性提高铸件的综合力学性能。研究结果表明： 在通常铸造条件下，母合
2、金的组织和重熔后铸件金相组织之间存在着必然的遗传联 系，粗大晶粒的母合金组织重熔后在不做其它特殊处理的条件下仍然保持粗大晶粒组织， 细小晶粒的母合金组织重熔后在不做其它特殊处理的条件下仍然保持细小晶粒组织。母合 金的组织遗传性只能在一定条件下保持，如果对熔体做特殊处理，则可以破坏其遗传性， 将 ZAlSi7MgY 合金熔体过热到 820865时，Si 相发生了类似于变质组织形态的变化， 同时 -Al 也得到细化，改善了母合金的组织状态。ZAlSi7MgY 合金重熔前后力学性能变 化不大，熔体过热到 865时，合金的综合力学性能最好。 利用 ZAlSi7MgY 合金的组织遗传性，通过向铸锭熔化后
3、的熔体中加入一定量的细晶压 铸件，可以有效细化重熔后铸件的晶粒，但是随着保温时间的延长细化效果逐渐减弱直至 消失。向合金铸锭熔化后的熔体中加入一定量的细晶压铸件可以显著提高合金的拉伸力学 性能， 添加 10细晶压铸件熔体保温 20min 时提高了 25， 提高了 50。 ZAlSi7MgY 熔体中包含细晶特征的原子集团不能稳定存在，随着保温时间的延长逐渐分解，当达到一 定的特性尺寸时将失去遗传特性。 随着冷却速率从 25/s 到 80/s 再到 260/s 的增加, ZAlSi7MgY 合金的宏观晶粒 尺寸减小,共晶 Si 相形态也变得细小,且分布更加弥散。 对于 ZAlSi7MgY 合金，采
4、用 545固溶处理时，合金的强塑性配合较好。固溶处理过 程中，Si 相和 Fe 相均要发生形态改变，其变化过程可以概括为尖端钝化、溶断和球化三 个阶段。提高固溶温度或延长保温时间，Si 相和 Fe 相的形态更为有利。因而合金的力学 性能得以提高，尤其是合金的塑性。因此可以通过固溶处理来消除有害遗传。 金属和合金的组织遗传性在很大程度上受到熔化工艺（熔化温度、保温时间等） 、熔 体处理工艺（过热、改变冷却速度等）和其它工艺因素的影响。这些工艺条件通过改变结 晶条件，改变了凝固后铸锭或铸件的组织和性能。 关键词：关键词：组织遗传，铸造铝合金，重熔，过热处理，保温时间，冷却速率，固溶处理 ZAlSi
5、7MgY 合金组织遗传性研究 ii THE STUDY OF MICROSTRUCTURE HEREDITY OF ZAlSi7MgY ALLOY ABSTRACT Many problems on casting quality to a great extent are originated from the quality of raw metal material, because the microstructure of raw alloy material takes direct effect to the microstructure of later alloy produ
6、ct, which is the problem now needed to be solved by gene engineer of metal also named heredity of metal microstructure. Now as a new subject either in theory or in technology, it takes great significance for improving casting quality, promoting alloy properties, and plotting reasonable technology. I
7、n this paper, focused on the study of heredity phenomenon of an aluminum alloy ZAlSi7MgY, several methods were adopted to investigate the heredity of this alloy microstructure, and then the overall properties of ZAlSi7MgY were improved by the heredity principle. The results are as follows: In genera
8、l cast condition, the microstructure of mother alloy can obviously transmit to child alloy after remelt, which means that, without special treatment, if the grain of mother alloy is coarse, the grain of remelt alloy is also coarse; if the grain of mother alloy is fine, and the grain of remelt alloy
9、is also fine. The heredity of mother alloy can only exist under certain conditions, if the melt was specially treated, the heredity will damage. When ZAlSi7MgY alloy was superheated to 820865, the morphology of Si phase was changed into a structure. Like that of the phase after modification, and -Al
10、 also was fined, overall, the morphology of the mother alloy was improved. However, if by remelting, the mechanical properties have little change, but by superheated at 865, the alloy has the best overall mechanical properties. Based on heredity of ZAlSi7MgY alloy, by adding a certain quantity of th
11、in plates, being made from forging liquid alloy, to melt, the casting grain can be effectively refined; but with the delay of the time of the temperature holding, the refining effect is gradually reduced and vanished. Adding a certain quantity of thin plates can also obviously improve mechanical pro
12、perties, for example, in the paper, after adding 10% thin forging plates into the melt, and keeping 20 minutes, was increased 25%, and 50%. In ZAlSi7MgY melt, the atom cluster with the feature tending to form into fine grain is unstable, and is to decompose as the temperature is keeping for a long t
13、ime. And when the size of the atom cluster goes smaller than a certain number, the heredity will die down. With the cooling rate increases from 25/s to 80/s then to 260/s, the grain size will decrease, and the morphology of Si in eutectic phase be fined, and disperse more even. When treated by solid
14、 solution strengthen at 545, ZAlSi7MgY alloy have either good strength or good ductility. In the course of solid solution treatment, the morphology change will take place both for Si phase and Fe phase which will turn their shape from needlelike into spherelike. If increasing solid solution temperat
15、ure or delay the temperature holding time, the 河北工业大学硕士学位论文 iii shape of Si phase and Fe phase are more rounder, so that its mechanical properties are surely increased, especially its elongation. On the whole, the harmful heredity may be removed through solid solution. The microstructure heredity of
16、 metal or alloy are affected by melt technology (say melt temperature or temperature holding time), treatment technology for melt (superheat or changing cooling rate, etc), and other technological factors. Such technological conditions can alter the solidification conditions to alter the microstructure and properties of castings. KEY WORDS: microstructure heredity,cast aluminum alloy, remelt, superheat treatment, tempe
