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热速处理对Al7SiMg合金组织和力学性能的影响

The Effect on the Microstructure and Mechanical Properties of Al7SiMg Alloy by Thermal Rate Treatment

【作者】 章国伟

【导师】 王宏伟;

【作者基本信息】 哈尔滨工业大学 , 材料加工工程, 2008, 硕士

【摘要】 本文选用Al7SiMg合金为研究对象,研究了不同细化、变质工艺和浇注工艺条件下热速处理对Al7SiMg合金组织和力学性能的影响。采用OLYMPUS光学显微镜和S5700扫描电子显微镜观察了合金的晶粒度和显微组织,采用INSTRON1186电子万能拉伸试验机测试了各种工艺浇注条件下合金的力学性能,。结果表明,在单一细化条件下,经热速处理后的合金晶粒最细小,抗拉强度最高,达到了164MPa,比正常浇注的合金抗拉强度提高近13MPa;经热速处理后合金延伸率达到了2.3%,与正常浇注的合金延伸率相近。热处理后,经热速处理的合金抗拉强度比空冷至低温浇注的合金提高了8.6%,。在单一变质条件下,经热速处理后的合金晶粒最小;经热速处理后的合金抗拉强度最高,达到了168.5MPa,比正常浇注的合金抗拉强度提高了18MPa,比空冷至低温浇注的合金强度提高了近8MPa;正常浇注的合金与经热速处理至低温浇注的合金延伸率都在4.2%左右;热处理后,经热速处理后的合金抗拉强度比空冷至低温浇注的合金提高了5.1%。在综合细化变质的条件下,经热速处理的合金共晶硅呈颗粒状,而其它浇注工艺的合金共晶硅还是呈短棒状;经过热处理后合金中的共晶硅都呈了颗粒状,其中热速处理的合金共晶硅还有部分呈短棒状,原因是颗粒状共晶硅开始长大;铸态下合金的抗拉强度,屈服强度和延伸率都达到了最佳,分别达到了181.8MPa,101MPa和4.2%;热处理后,经热速处理后的合金抗拉强度比空冷至低温浇注的合金提高了3.1%。经热速处理的合金金属型铸造后,合金的各项性能都达到了最佳,抗拉强度超过了360MPa,延伸率超过了14%,是所有合金中综合力学性能最佳的合金。

【Abstract】 In this paper, we investigated the properties of Al7SiMg alloys. we want to find the differences of microstructure and the mechanic properties of the alloys which cast at normal temperature, air cooling to low temperature and thermal rate treatment to low temperature. We use OLYMPUS optical microscope to observe the microstructure of the alloy, use INSTRON1186 to test the mechanical properties of alloy poured of different processes.The differences of casting at 720℃,air cooling at 640℃and thermal rate treatment on the mechanical property of refining Al7SiMg alloy has been studied. Research finds out that after thermal rate treatment the alloy refined obviously. Grain size was the smallest by thermal rate treatmented alloy. After thermal rate treatment the tensile strength was the largest, reached 164MPa, it was increased 13MPa comparatively 720℃casting. The elongations was the like to the alloy after thermal rate treatment and air cooling alloys, they reached 2.3%. After heat treatment, the tensile strength by thermal rate treated alloy increased 8.6% than air cooling to low tempetature.The difference between casting at 720℃,air cooling at 640℃and thermal rate treatment which casting at 640℃on the mechanical property of modification Al7SiMg alloy also has been studied. The result found out that after thermal rate treatment, the grain was the smallest. After thermal rate treatment the tensile strength was increased 18MPa comparatively by high temperature casting. And it was increased 8MPa comparatively by air cooling casting. The elongations was the the like to the alloy after thermal rate treatment and air cooling alloys, they reached 4.2%. After heat treatment, the tensile strength by thermal rate treated alloy increased 5.1% than air cooling to low tempetature.The differences between casting at 720℃, air cooling at 640℃and thermal rate treatment which casting at 640℃on the mechanical property of refining and modification Al7SiMg alloys has also studied. we find that the eutectic silicon became granule after thermal rate treatment while the others still was cosh. After heat treatment ,the eutectic silicon of all the alloys became granule. After hot treatment, the tensile strength by thermal rate treated alloy increased 3.1% than air cooling to low tempetature.The thermal rate treated alloy which casting by permamental molding was the best of all the properties, the tensile strength exceeded 360MPa, and the elongation exceeded 14%.

  • 【分类号】TG166.3;TG146.21
  • 【下载频次】71
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