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1、西北工业大学工学硕士学位论文AbstractDuringthesemi-solidforming,themicrostructureinmaterialsundergoesaseriesofdynamicchanges,whichwillafectthedeformationbehaviorofmaterialsandservicingpropertiesofworkpieces.Tounderstandtheofprocess0nmicrostructurevariables,andexplorethedeformationmechanismandestablishth
2、emodelformicrostructuralevolutioninthesemi-solidformingcanprovidethetheoreticalandtechnologicalfoundationforoptimizingtheprocessparametersanddevelopingthesemi-solidtechnique.Efectoftheprocessparameters,includingdeformationtemperature,heightreductionandstrainrate,onmicrostructurevariables,
3、includingthegrainsizeandthefractaldimension,hasbeeninvestigatedbytheisothermalcompressionandquantitativemetallographyexamination.Thedistinctionsofmicrostructurebetweenthesemi-solidformingandhightemperaturedeformationoftheAl-4Cu-Mgalloyasreceivedandsemi-solidAl-4Cu-Mgalloyhasbeeninvestigat
4、ed.Meanwhile,thesemi-soliddeformationmechanismhasbeeninvestigatedbyTEMandSEM,andthedefectivestructure,includingcavity,liquidphasesegregationandconstituentsegregation,hasbeeninvestigated.Intheend,integratingtheadvantagesofthefuzzysetandtheartificialneuralnetworktheory,amicrostructuralevolu
5、tionmodelduringthesemi-solidforminghasbeenestablishedaccordingtotheexperimentalresults.Meanwhile,thepresentmodelischecked.Thecomparisonofthecalculatedresultswiththeexperimentalofthetestsamplesshowsthatthemaximunerrorofgrainsizeislessthan10%,andwhichoffractaldimensionislessthan15%.Themicro
6、structuralvariablesofAl-4Cu-Mgalloyhasbeencalculatedduringsemi-solidforming.Keywords:Al-4Cu-Mgalloy;semi-solidforming;deformationmechanismmicrostructuralevolutionmodel西北工业大学工学硕士学位论文第1章绪论铝及铝合金简介1.1.1铝及铝合金的特点和应用铝是地壳中储量最丰富的金属材料,铝及铝合金具有良好的综合性能,因此在一系列应用领域中显示出许多胜于钢和铜合金的重要优点。在战后的整个时期内,铝的增长速度超过钢,
7、铝的年生产规模仅次于钢而跃居于第二位[III。在国民经济的各个领域,特别是航空航天、交通运输、建筑等领域,铝及其合金发挥了巨大作用。铝及其合金的广泛应用,除了其储量丰富的原因以外,更重要的是其具有优良的综合性能。慨括起来,铝及其合金的特点可以归纳为[x"21,1)密度小、同等体积的铝的重量只有钢铁的三分之一左右。2)耐腐蚀性好,化学性能比较稳定,表面氧化层可以起到良好的保护作用,不易与空气、水等发生反应。3)具有良好的导电性和导热性能。4)比强度高,某些铝合金的强度等于甚至超过普通碳素结构钢。5)铝的塑性很好,容易加工成形,可