复合细化变质和热处理对A356合金组织及磨损性能的影响

发布时间：2018-02-15 19:51

本文关键词： A356合金复合细化变质处理 T6热处理显微组织力学性能摩擦磨损磨损机理　出处：《江苏大学》2016年硕士论文　论文类型：学位论文

【摘要】：本文通过氟盐铝热法自制的Al-5Ti-1B-1RE中间合金作为细化剂,与Al-10Sr变质剂对A356合金进行复合细化变质处理,并对铸态A356以及最佳复合细化变质处理的A356进行T6热处理,制备出四组A356试样。利用金相显微镜、电子扫描电镜、能谱仪等多种现代分析手段,对复合细化变质的A356合金的显微组织、共晶Si相形态及分布,探讨了Al-5Ti-1B-1RE细化剂和Al-10Sr变质剂的最佳添加量;然后用箱式热处理炉对铸态A356以及最佳复合细化变质处理的A356进行T6热处理,制备出1#铸态A356、2#T6态A356、3#复合细化变质态A356、4#复合细化变质后T6热处理态A356四组试样,对其采用万能拉伸试验机分析测试了四组A356合金的力学性能;用M-2000型磨损试验机对四组A356合金进行了油润滑条件下的磨损试验,并对合金的摩擦磨损性能及磨损机理进行了初步分析。实验结果表明:添加0.8%Al-5Ti-1B-1RE细化剂和0.3%Al-10Sr变质剂后经过T6热处理的A356晶粒组织更加细小,圆整、圆润的共晶Si相及金属间化合物均匀的分布在α-Al相周围,其抗拉强度σb为275MPa,比铸态A356提高了44.7%,延伸率δ为5.4%,提高了2.6倍,α-Al相显微硬度为74HV,提高了27.6%。在细晶强化、固溶强化、时效强化以及晶界强化的共同作用下,4#复合细化变质后T6热处理态A356力学性能非常优异。铸态A356的耐磨性最差,同等条件下,磨损率和单位时间磨损量都是最高的,复合细化变质后经T6热处理的A356耐磨性最好,相对应的磨损率和单位时间磨损量都是最低的。随着载荷和时间的增加,铸态A356的磨损机理演变过程为磨粒磨损→粘着磨损→严重粘着磨损→剥层磨损;复合细化变质后经T6热处理的A356的磨损机理演变过程为轻微磨粒磨损→微切削磨粒磨损→磨粒磨损→磨粒磨损+粘着磨损→粘着磨损。复合细化变质和T6热处理的A356合金耐磨性的提高,一方面细晶强化、晶界强化、固溶强化、时效强化以及变质作用,提高了A356的强度硬度,减缓了磨面摩擦热所产生的组织软化,减轻了磨面亚表层的塑性变形;另一方面摩擦过程中生成的高硬度Al2O3颗粒,此氧化膜在微凸体后最先承受正压力和剪切力,尽量减少α-Al基体与GCr15摩擦副的直接接触,从而保护α-Al基体。
[Abstract]:In this paper, Al-5Ti-1B-1RE master alloy made by aluminothermic method was used as refiner, and Al-10Sr modifier was used to refine and modify A356 alloy, and the as-cast A356 and A356 were treated by T6 heat treatment. Four groups of A356 samples were prepared. The microstructure, morphology and distribution of eutectic Si phase of the modified A356 alloy were studied by metallographic microscope, electron scanning electron microscope and energy spectrometer. The optimum addition amount of Al-5Ti-1B-1RE refiner and Al-10Sr modifier was discussed, and then the as-cast A356 and the best compound refining modification A356 were treated with box heat treatment furnace for T6 heat treatment. Four groups of A356 samples of as-cast A356T2#T6 A356HZ compound refined modified A356a- modified T6 heat treated state A356 were prepared, and the mechanical properties of the four groups of A356 alloys were analyzed and tested by universal tensile testing machine. The wear tests of four groups of A356 alloys under oil lubrication were carried out with M-2000 wear tester. The tribological properties and wear mechanism of the alloy were preliminarily analyzed. The experimental results showed that the microstructure of A356 after T6 heat treatment was finer and more rounded after adding 0.8Al-5Ti-1B-1RE refiner and 0.3Al-10Sr modifier. The smooth eutectic Si phase and intermetallic compounds distribute uniformly around 伪 -Al phase. The tensile strength 蟽 _ b is 275MPa, the tensile strength 蟽 _ b is 275MPa, the elongation 未 is 5.446 times higher than that of as-cast A356, and the elongation 未 is 5.40.The microhardness of 伪 -Al phase is 74HVand the hardness of 伪 -Al phase is increased 27.66.In fine grain strengthening, solid solution strengthening, The mechanical properties of T6 heat treated state A356 are very excellent under the combined action of aging strengthening and grain boundary strengthening. The wear resistance of as-cast A356 is the worst, and the wear rate and wear amount per unit time are the highest under the same conditions. The wear resistance of A356 after T6 heat treatment was the best, and the wear rate and wear amount per unit time were the lowest. With the increase of load and time, the wear mechanism of as cast A356 evolved into abrasive wear. 鈫扐dhesive wear. 鈫扴evere adhesive wear. 鈫扵he wear mechanism of A356 after T6 heat treatment is slight abrasive wear. 鈫扢icro cutting abrasive wear. 鈫扐brasive wear. 鈫扐brasive wear. 鈫扐dhesion wear. The wear resistance of A356 alloy modified by composite refinement and T6 heat treatment is improved. On the one hand, fine grain strengthening, grain boundary strengthening, solid solution strengthening, aging strengthening and modification can improve the strength and hardness of A356. On the other hand, the high hardness Al2O3 particles formed in the friction process are first subjected to the positive pressure and shear force after the micro-convex body, and the microstructure softening caused by the friction heat of the wear surface is reduced, and the plastic deformation of the subsurface layer of the wear surface is alleviated, on the other hand, the high hardness Al2O3 particles formed during the friction process, The direct contact between 伪 -Al matrix and GCr15 friction pair is minimized to protect the 伪 -Al matrix.
【学位授予单位】：江苏大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TG292;TG115.58

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