Sr变质剂和浇铸冷却速率对铸铝A319微观组织及力学性能的影响

本文以A319合金作为研究对象,通过在合金熔体中添加变质剂、分层铸造以及对铸造后的合金进行T6热处理等方法来研究这些因素对合金显微组织和性能的影响.本文的主要研究内容包括:(1)研究了Sr变质剂对铸造A319铝合金的微观组织和力学性能的影响.结果发现Sr变质过的合金中硅颗粒的大小和长径比显著减小,得到了很好的粒状化效果...     

Cooling slope casting to produce EN AW 6082 forging stock for manufacture of suspension components

The potential of cooling slope casting process to produce EN AW 6082 forging stock for the manufacture of EN AW 6082 suspension components was investigated. EN AW 6082 billets cast over a cooling plate offer a fine uniform structure that can be forged even without a separate homogenization treatment. This is made it possible by the limited superheat of the melt at the start of casting and the fractional solidification that occurs already on the cooling plate. Suspension parts forged from cast and homogenized billets with or without Cr all showed a uniform structure, and the hardness reached HV 110 after the standard artificial ageing treatment.     

THERMAL RATE TREATMENT AND ITS EFFECT ON MODIFICATION OF Al-Si ALLOYS

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Effect of heat treatment on shape memory properties of ductile CuAlMn alloys

1　ＩＮＴＲＯＤＵＣＴＩＯＮＣｕ ｂａｓｅｄｓｈａｐｅｍｅｍｏｒｙａｌｌｏｙｓ (ＳＭＡｓ)ａｒｅｃｏｍ ｍｅｒｃｉａｌｌｙａｔｔｒａｃｔｉｖｅｓｙｓｔｅｍｓｆｏｒａｐｐｌｉｃａｔｉｏｎｓｂｅｃａｕｓｅｏｆｔｈｅｉｒｌｏｗｅｒｃｏｓｔ.Ｕｐｔｏｎｏｗ ,Ｃｕ ＺｎａｎｄＣｕ ＡｌｂａｓｅｄＳＭＡｓｈａｖｅｂｅｅｎｗｉｄｅｌｙｓｔｕｄｉｅｄ .Ｈｏｗｅｖｅｒ,ｔｈｅｓｅＣｕ ｂａｓｅｄａｌｌｏｙｓ,ｅｓｐｅｃｉａｌｌｙｔｈｅａｌｌｏｙｓｏｆＣｕ Ａｌ ＮｉｓｙｓｔｅｍａｎｄｔｈｅｏｎｅｓｗｉｔｈｈｉｇｈＡｌｃｏｎｔ…     

硅相形态及含量对Al-Si合金线膨胀系数的影响

利用金相显微镜、DIL402C高温膨胀仪等对Al-Si合金的线膨胀进行了研究。结果表明：对于Al-Si合金,硅含量越高,其线膨胀系数越小,随温度变化幅度减小;随着温度升高,磷变质比锶变质的线膨胀系数变化幅度小,合金更加稳定;此外,T6热处理也显著降低Al-Si合金的线膨胀系数。通过对合金线膨胀系数和微观组织的对比观察发现：硅相的形态和体积分数对Al-Si合金的线膨胀系数产生重要影响。初晶硅体积分数的增加和初晶硅的析出能够显著降低Al-Si合金的线膨胀系数,共晶硅的形态对合金线膨胀系数也有一定的影响,共晶硅为短棒状、颗粒状时（尤其经热处理后）,合金的线膨胀系数也显著降低。     

Aging of an aluminum alloy resulting from variations in the cooling rate

The effect that the rate of cooling after solubilization exerts on the aging behavior of an aluminum heat treatable alloy was studied. Bars of the alloy were heated in a box furnace for solubilization, and after this was achieved they were cooled to room temperature by placing one end in a shallow tank of water. Thermal evolution along the bar was registered with the aid of thermocouples connected to a PC-based data logging system. Small samples were cut from the bars and aged for different times and temperatures. Results from microhardness tests indicate that peak hardness, at a given aging temperature, augments with the increase of the cooling rate until a certain value is achieved, above which the hardness remains constant. This feature was found to be due to precipitation taking place at the lower cooling rates.     

快速加热循环热处理细化TiAl基合金的显微组织研究

在研究Ti－Al二元相图及合金元素的影响、TiAl基合金显微组织类型与连续冷却转变、热处理实践及效果的基础上，提出了快速加热循环热处理新工艺，该工艺的特点是：加热速度快，单相构保温，保温时间短，冷却速度相对较慢。分析了该工艺的优点和缺点。     

铝-硅基复合材料中硅相组织形态影响因素研究

对不同的工艺条件下制做的铝-硅基复合材料中硅相组织进行了研究。结果表明，冷却速度增大，热处理保温时间适当增长都会使基体组织中的硅相形态由块状向粒子状转变，促使硅相细化；另外，提高热处理温度使复合材料出现新相(α-Al)；凹曲面的增强相表面形态有利于细化复合材料组织。     

ZL101合金的变质

采用扫描电镜, 对ZL101合金的Sr变质效果与保温时间、 Sr含量及晶粒尺寸的关系进行了研究. 结果表明 ZL101共晶硅的Sr变质具有长效性, 且达到最佳变质效果前有一时间间隔;加入的Sr量有一临界值, 超过此值, 变质效果变化不明显; 若共晶硅越细小, 变质效果则越好, 达到最佳变质效果的时间也随之缩短.     

Effect of Retained Austenite on Properties of Austempered Ductile Iron

Austempered ductile iron (ADI) exhibits a favourable combination of strength and toughness, and has been used as a substitute for quench-tempered or carburise-quenched steel. A characteristic feature of bainite transformation of cast iron, as opposed to carbon steel, is that precipitation of carbide is suppressed by the high concentration of silicon. Thus, a favourable structure, consisting of bainitic ferrite and retained austenite without carbide, can be provided by the optimum austempering treatment. Such microstructure and the mechanical properties of the iron are significantly affected by the conditions of the austempering treatment and the chemical composition. In this study, several grades of ductile iron were austempered under various conditions. The relationship between the impact strength, the quantity of retained austenite and the isothermal transformation curve was investigated. The stability of the retained austenite is considered important, because ADI contains a large amount of retained austenite which contributes to the improvement of ductility and toughness and which may transform to martensite when held at low temperature or subjected to stress. In this study, the stability of the retained austenite at low temperatures was examined by holding or stressing to establish the relations between transformation and temperature, stress and strain.

When the austempering time is short, the untransformed austenite partially transforms to martensite during air cooling, due to the lower carbon content, resulting in lower impact strength. As the austempering time increases, the untransformed austenite is stabilised by carbon-enrichment and there is little transformation to martensite, resulting in a large amount of retained austenite and higher impact strength. When the austempering time becomes much longer, the carbon-enriched austenite decomposes, presumably to bainitic ferrite and carbide, decreasing impact strength. In increasing the silicon content, precipitation of carbide in bainite is suppressed and both the maximum impact value and the content of retained austenite increase. The decreasing rates after the maxima through an additional isothermal holding becomes smaller.

By holding at temperatures down to –40°C, the decrease in retained austenite and the increase in hardness are both small. The retained austenite is stable under stress lower than that required to cause plastic deformation. Compressive stress hinders the martensitic transformation, because the transformation is accompanied by volume expansion.     

La变质和热处理复合作用下ZL107铝合金中Si相形态演化及其力学性能(英文)

研究ZL107铝合金经过固溶和时效处理后的Si相形态演化及其对力学性能的影响。结果表明,当合金在560°C固溶处理6h后,有部分Si相固溶进入基体,但在随后的时效过程中Si相会重新析出。比较了变质和未变质ZL107合金的固溶时效过程。通过La变质处理再固溶时效,ZL107合金中的Si相形态明显细化,合金的力学性能提高幅度更大。     

成分和工艺因素对Mn-Cu合金阻尼性能的影响

考察了化学成分、热处理工艺及铸造冷却速度对Mn-Cu合金阻尼性能的影响.试验结果表明,铝的影响与热处理状态密切相关,硅是有害的,加入稀土可提高阻尼性能.随着铸造冷却速度的加快,合金的阻尼性能降低.依据成分等情况提出了较佳的热处理工艺.     

高频电阻焊管用低强度钢的热处理工艺

采用Gleeble-3500型热模拟试验机研究了加热速度、加热温度以及冷却速度对高频焊管用钢的组织和性能的影响规律。结果表明:加热速度对奥氏体相变点有显著影响,随加热速度的提高,相变点呈线性增加。在850～1000℃范围内,当加热温度达到925～950℃时,强度达到最低值。随加热温度进一步升高,强度增加。随冷却速度的降低,钢的强度显著下降,组织粗化,且出现带状组织。     

Assessment of modification level of hypoeu- tectic Al-Si alloys by pattern recognition of cooling curves

1 Introduction Due to their excellent castability and good mechanical properties, Al-Si alloys are the most important and most widely used casting aluminum alloys. A further increase in mechanical properties can be achieved by means of a modification treatment with Na or Sr. Without this treatment, the eutectic silicon crystallises into an acicular or lamellar morphology with poor properties; when a modifying element is added, it becomes a very fine and fibrous silicon network resulting in a…     

镁合金的热处理

介绍了镁合金的热处理类型,综述了不同镁合金系合金化和热处理时的显微组织特点,以及合金元素对时效析出过程及合金性能的影响。最后提出了镁合金热处理未来的研究和发展方向。     

Impact properties of A356-T6 alloys

The Charpy impact energy of A356 alloys has been measured. Instrumented Charpy impact tests have been conducted at 25,100,150, and 200 °C. The Charpy specimens were machined from plate castings ortapered cylindrical castings. The plates were produced in sand molds, and tapered cylinders were produced in water-cooled copper molds. Both unmodified and strontium-modified castings were tested. The results indicate that strontium modification improves the impact properties of sand and permanent mold castings. The impact energy increases with solution treatment time. Strontium modification reduces the solution treatment time for attaining a specific impact property level in the casting.     

Mg量对过共晶Al-18%Si合金组织与性能的影响

为改善Al-18％Si组织形貌,利用扫描电镜与金相显微镜观察了不同含Mg量过共晶Al-Mg-18％Si合金的显微组织,并测试相应的力学性能,研究了强化处理的作用。结果表明:镁在过共晶Al-Si合金中的作用是通过热处理来实现,随镁含量的增加,合金的强度稍有增加,但伸长率有所下降。为了提高金相组织与力学性能,Mg量应控制在0．5％-3．0％。     

硅酸铝短纤维增强铝硅合金复合材料热处理组织的研究

研究了热处理工艺对硅酸铝短纤维增强铝硅合金复合材料组织的影响.试验结果表明,热处理能改善复合材料的显微组织,保温时间适当延长可使复合材料组织变细小.另外,热处理温度与制备复合材料的冷却速度增大会导致复合材料处理后新相组织的产生,这是由于冷却速度的增大导致共晶温度下降引起的.经适当的热处理后,复合材料的力学性能有不同程度的提高.     

热处理对新型Al-Mg-Si合金微观组织及性能的影响

对4种通过热力学计算优化选出的Al-Mg-Si合金进行了电磁搅拌及热处理试验研究。通过微观组织和性能的分析比较发现,电磁搅拌能显著改善合金的显微组织结构,为后续的热处理提供有利的显微组织条件,进而增强合金的时效强化效果,改善合金的塑性。同时发现,Mg、Si含量对合金的显微组织和性能具有不同的影响,这与合金不同的平衡凝固过程有关。该试验研究为进一步优化适合半固态成形的低成本高性能铝合金提供了依据。     

含锶镁合金组织和性能的最新研究进展

锶作为一种应用潜力较大的镁合金合金化元素,已在镁合金中的应用研究领域引起国内外的广泛关注和高度重视.国内外近几年来的研究工作主要集中在锶对镁合金晶粒细化、第二相改性和含锶耐热镁合金的发展等方面.对国内外含锶镁合金研究工作的最新进展进行综述,介绍重庆大学近几年在含锶镁合金方面的最新研究成果,讨论若干新型含锶镁合金的组织和...