SiCw／LD2复合材料超塑变形过程中的孔洞演化规律

用挤压铸造法制成ＳｉＣｗ／ＬＤ２复合材料,在４７０℃下进行热挤压得到板材,挤压比为１：２２在５７０℃进行超塑拉伸实验,应变速率同８．３３＊１０＾－４ｓ＾－１逐步升到８．３３＊１０＾－３ｓ＾－１,在４．１７＊１０＾－３ｓ＾－１时获得了２８０％的最大延伸率。     

25SidCw／LD2复合材料超塑变形过程中位错的分布规律

采用挤压铸造法制成复合材料并热挤压成板材，然后对其进行了超塑拉伸实验。当拉伸温度为570℃，应变速率为2.0×10     

25SiC_w/LD2复合材料超塑变形过程中位错的分布规律

采用挤压铸造法制成复合材料并热挤压成板材 ,然后对其进行了超塑拉伸实验。当拉伸温度为5 70℃ ,应变速率为 2 .0× 10 -3s-1时获得了 2 80 %的延伸率 ,用TEM观察了超塑变形过程中位错的变化分布规律。结果表明 ,位错的密度及分布与变形温度及应变速率有一定关系。在最佳变形条件下 ,变形初期位错主要集中在晶界处分布 ,随着变形量的加大 ,位错向晶粒中间扩展 ,并发现有层错及孪晶出现 ,这对协调变形具有一定作用。     

SiCp／LD2复合材料的微区力学性能

用ＵＭＨＴ３ 型超显微硬度仪测试ＳｉＣｐ／ＬＤ２ 复合材料界面附近基体中的硬度值, 结果表明,由于热膨胀系数差异, 复合材料中的热残余应力超过基体的屈服极限, 导致界面附近基体内存在热残余应变, 并使基体应变硬化, 因而超显微硬度值的变化可以反映热残余应变的分布状况。界面附近基体的超显微硬度随颗粒尺寸、距界面的距离和颗粒的尖锐程度而变化, 与有关复合材料中热残余应变分布的计算结果吻合。     

THE REINFORCING MECHANISM OF TiB2 IN TiB2／A357 COMPOSITE

Mechanical properties were tested for in situ TiB2/A357 composite fabricated by LSM (mixed salts reaction) method. Micro structures of as cast and plastic deformed TiB2/A357 were investigated. The results show that there is a low misfit between (200) Al and (101)TiB2 with [011]//Al [101]TiB2. There is a change from fully dendritic structure of the α-Al of A357 to a rosette-type structure of TiB2/A357. Significant increases in proof stress and Young's modulus can be obtained at low TiB2 additions. There exist dislocation loops around neighboring TiB2 particles with about 0.1μm in diameter and dislocation multiplication near TiB2 particles.     

SiCp／LY12复合材料的超塑性变形特性

对ＳｉＣｐ／ＬＹ１２复合材料在超塑性变形前后的内部组织、超塑性断裂延伸率、ｍ－δ关系进行了研究，并分析了其原因     

GRAIN BOUNDARY CHARACTER DISTRIBUTION, TEXTURE AND SUPERPLASTIC DEFORMATION BEHAVIOR OF AN AI-Li ALLOY

The grain boundary character distribution and thetexture of 2091 Al-Li alloy recrystallized at different temperatures were measured by TEM and X-ray techniques respectively. The occurrence frequency of low-energy boundaries decreases with increasing recrystallization temperature, while the frequency of highenergy boundaries increases. The strongest component of recrystallization texture in the test temperature range is {011} <111>. The relative intensity of the texture tends to decrease with increasing recrystallization temperature. The material which contains a high frequency of low-energy boundaries exhibits lower deforming stress and high elongation.     

GRAIN BOUNDARY CHARACTER DISTRIBUTION, TEXTURE AND SUPERPLASTIC DEFORMATION BEHAVIOR OF AN Al-Li ALLOY

１ＩＮＴＲＯＤＵＣＴＩＯＮＴｈｅｓｕｐｅｒｐｌａｓｔｉｃｉｔｙｉｓｒｅｌａｔｅｄｔｏｔｈｅｈｉｇｈｔｅｍｐｅｒａｔｕｒｅｄｅｆｏｒｍａｔｉｏｎｂｅｈａｖｉｏｒｏｆｓｕｐｅｒｐｌａｓｔｉｃｍａｔｅｒｉａｌｓｓｏｔｈａｔｔｈｅｇｒａｉｎｂｏｕｎｄａｒｙｂ...     

SiCp/2024铝基复合材料的超塑性变形行为研究

对经过热处理和冷轧后的体积分数为17％，尺寸为3．5μm的SiC颗粒增强2024铝合金薄板在753－853K范围内进行了超塑性实验研究. 结果在813K时以10^-1/S的变形速率下获得了259％的最大延伸率，最大应力敏感系数为0．25复合材料的变形激活能值在753－793K范围内为144kJ/mol，在813－853K内为202kJ/mol，接近纯铝的晶格扩散激活能值142kJ/mol。复合材料的变形机制主要为基体晶粒滑动机制。     

2214铝合金超塑性变形机制

温轧态２２１４铝合金在超塑性变形过程中，由于动态回复和动态再结晶的作用，使晶内位错密度在一定程度上保持平衡。超塑性变形的主要机制为晶界滑动；晶内位错滑移和扩散蠕变作为重要的协调机制，促进了晶界滑动的顺利进行。该合金的超塑性变形机制符合位错协调晶界滑动模型。     

HIGH STRAIN RATE SUPERPLASTICITY IN A SiC_w/2024Al COMPOSITE MADE BY SQUEEZE CASTING

1.IntroductionHighStrainratesuperplasticity(HSRS)infineceramicwhiskerorparticulatereinforcedaluIninUIncompositesisveryattractipeforcommercialaPplicationsbecausetheHSRScompositesusuallyeallibitatotalelongation0f25M00%atahighstrainrate0f>10-2s-1Il-7]andoneofcurrentdrawbacksinsuperPlasticformingteclm0logyisaslowf0rIIilngratewhichistypically10-5-10-3s-1.Forindustrialfabricati0nofceramicwhiskerreinforcedaJumintuncomposites,squeezec88tingprocedureismorecost-ethetivethanpowdermetallurgy(P/M)m…     

FRACTAL DIMENSION OF SHAPE CHANGE OF CAVITIFS DURING SUPERPLASTIC DEFORMATION IN HIGH STRENGTH Al ALLOY

The fractal dimension changes of cavities have been determined during superplasticdeformation of the high strength aluminiurn alloy 7475 with different strain,temperature,strain rate and grain size.The fractal dimension of cavities may increase with the increase ofstrain.It becomes higher as the alloy deformed under lower temperatures,greater strain rateand coarser grain size.The alloy would be approaching to rupture if the fractal dimension ofcavities raised to a certain extent.     

TiB_2/SiC_w陶瓷复合材料的研究

采用热压工艺制备了TiB_2／SiC_w陶瓷复合材料。在TiB_2基体中添加适量的SiC_w晶须，可显著的提高材料的断裂韧性和抗弯强度。采用有限元法计算了由于基体和晶须熟膨胀系数失配所产生的残余应力及其分布，分析热胀失配所产生的残余应力对材料增韧特性的影响。结果表明：晶须径向及轴向均受残余压应力的作用；晶须拔出和桥联为该复合材料的主要增韧机制。