凝固条件和热处理对耐热铝铜合金组织和性能的影响

发布时间：2018-06-16 20:53

本文选题：耐热铝合金 + 热处理　；参考：《哈尔滨工业大学》2017年硕士论文

【摘要】：本文采用砂型低压铸造的方法,浇注出不同壁厚和不同冷铁条件下凝固的耐热铝铜合金铸件,在此基础上利用正交实验法对合金热处理参数进行了优化,并研究了不同壁厚和冷铁条件对合金组织和性能的影响。根据正交实验结果分析,三个热处理参数中,时效温度对耐热铝铜合金性能的影响最大,时效时间对合金室温抗拉强度影响最小,但其对合金高温抗拉强度的影响较大,固溶时间对合金的高温性能影响最小。综合考虑,本文最终确定Al-5.0Cu-1.5Ni-0.35Mn-0.35Co-0.25Sb-0.22Ti-0.22Zr合金最佳的热处理工艺参数为为固溶温度535℃,固溶时间10h,80℃水温淬火,时效温度190℃,时效时间14h。通过实验对正交优化结果进行验证,结果表明经最优热处理参数处理后的合金室温性能和高温性能均达到最高值,室温拉伸抗拉强度为319.39MPa,屈服强度201.53MPa,延伸率8.52%;300℃高温抗拉强度为151.19MPa,屈服强度为129.03MPa,延伸率为16.66%,证明正交实验的结果是可信的。研究了不同壁厚对耐热铝铜合金铸件组织和性能的影响,结果表明:在铸态下,随着壁厚的增加,合金组织中第二相的百分含量减少,晶粒粗化,且第二相分布不均,聚集现象严重;铸件的硬度、抗拉强度和屈服强度均会随着壁厚的增加而下降,而延伸率会有所提升。热处理后,随着壁厚的减小,铸件组织得到改善,砂型20mm厚铸件室温抗拉强度为271.55MPa,300℃高温抗拉强度为136.30MPa,而砂型10mm厚铸件室温抗拉强度为286.46MPa,300℃高温抗拉强度为138.92MPa,力学性能均有所提高。研究了不同冷铁条件对耐热铝铜合金铸件组织和性能的影响,结果表明:冷铁的使用增加了铸件的冷却速度,对铸件铸态组织的细化效果较壁厚而言更为明显,采用冷铁能够使铸件析出更多的第二相,并且经热处理后第二相分布的更弥散,对铸件性能有较好的改善作用。对比热处理前后组织,发现热处理后组织中的第二相百分含量明显减少,部分已经溶入基体中,基体内部的元素偏析也基本消除。热处理后的晶界要比铸态的晶界窄,且不连续,但仍呈网状或骨骼状分布着,分布更加弥散;热处理后的晶粒明显粗化。
[Abstract]:In this paper, the heat resistant aluminum copper alloy castings with different wall thickness and different cold iron conditions were cast by sand mould low pressure casting. On this basis, the heat treatment parameters of the alloy were optimized by orthogonal experiment. The effects of different wall thickness and cold iron conditions on the microstructure and properties of the alloy were studied. Of the three heat treatment parameters, aging temperature has the greatest influence on the properties of heat-resistant aluminum and copper alloy, and aging time has the least effect on the tensile strength of the alloy at room temperature, but it has great influence on the tensile strength of the alloy at high temperature, and the time of solid solution has the smallest effect on the high temperature properties of the alloy. In this paper, the Al-5.0Cu-1.5Ni-0.35Mn-0.35Co-0.25Sb-0. is finally determined. The optimum heat treatment parameters of 22Ti-0.22Zr alloy are 535 C solid solution temperature, solid solution time 10h, 80 C water temperature quenching, aging temperature 190 C. Aging time 14h. is verified by the orthogonal optimization results. The results show that the temperature properties and high temperature properties of the alloy after the optimum heat treatment parameters reach the highest value and tensile at room temperature. The tensile strength is 319.39MPa, the yield strength is 201.53MPa, the elongation is 8.52%, the tensile strength of high temperature is 151.19MPa at 300 C, the yield strength is 129.03MPa, the elongation is 16.66%. The results of orthogonal experiment are credible. The effect of different wall thickness on the microstructure and property of the heat resistant aluminum copper alloy casting is studied. The result shows that the wall thickness is in the cast state. In addition, the content of the second phase in the alloy microstructure is reduced, the grain size is coarsened, and the distribution of the second phase is uneven, and the aggregation phenomenon is serious. The hardness, tensile strength and yield strength of the castings will all decrease with the increase of wall thickness, and the elongation will be improved. After heat treatment, the structure of castings is improved with the decrease of wall thickness, and the sand type 20mm thick castings are made. The tensile strength of room temperature is 271.55MPa, the tensile strength of 300 C is 136.30MPa, while the tensile strength of the sand type 10mm thick castings is 286.46MPa, the tensile strength at 300 C is 138.92MPa, and the mechanical properties are improved. The effect of different cold iron conditions on the microstructure and properties of the heat-resistant aluminum copper alloy castings is studied. The results show that the use of cold iron is increased. The cooling rate of castings is more obvious to the casting structure of the castings than the wall thickness. The use of cold iron can precipitate more secondary phases of the castings, and the distribution of the second phase after heat treatment is more dispersed and improves the performance of the castings. The content of the fraction is obviously reduced and the part has been dissolved in the matrix, and the segregation of elements inside the matrix is basically eliminated. The grain boundary after heat treatment is narrower and discontinuous than the cast grain boundary, but it is still distributed in the net or skeleton, and the distribution is more diffuse, and the grain after heat treatment is obviously coarse-grained.
【学位授予单位】：哈尔滨工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG249.2;TG166.3

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