船用高镁铝合金腐蚀性能屈服行为及高温变形行为研究

【作者】 陈星霖；

【导师】 罗兵辉；

【作者基本信息】 中南大学 ， 材料学， 2009， 硕士

【摘要】 本文分三部分研究了加工工艺和退火对高镁5XXX系铝合金组织和性能的影响及Mg含量最高的5A01铝合金的热变形行为。第一部分通过组织检测,腐蚀和力学性能检测等实验手段,研究Mg含量和时效温度对固溶淬火态高镁铝合金组织和性能的影响规律。第二部分考察不同压下量和不同退火温度的冷轧态5456铝合金的腐蚀性能和屈服行为,确定高镁铝合金的腐蚀性能和屈服行为随压下量和退火温度的变化规律。第三部分采用Gleeble-1500热力模拟机对5A01合金进行等温恒应变热压缩实验,研究了5A01合金热变形流变应力行为,并建立流变应力的数学模型。通过实验数据的分析比较,得到以下结果:1.在同样Mg含量的情况下,固溶淬火态高镁铝合金在经过150℃时效后析出了大量粗大的,无规则分布的β相,经过350℃时效后β相基本溶解,但样品在时效后的空冷过程中生成了少量的细小的β相。因此在腐蚀性能方面,经过150℃时效后的样品的应力腐蚀敏感性比淬火态和经过350℃时效的同样Mg含量的样品都要高,且抗晶间腐蚀能力最差。随着Mg含量的增加,合金中析出的β相越多,合金的应力腐蚀敏感性增加,抗晶间腐蚀能力降低;在屈服行为方面,经过150℃时效的样品由于析出大量的β相导致固溶体中的Mg含量降低,从而使得经过150℃时效的样品的的锯齿屈服强度比淬火态和经过350℃的样品都要小,同时,时效的时间越长,固溶体中的Mg含量越低,锯齿强度越低。2.对于不同压下量冷轧态的5456铝合金,由于残余应力的存在,冷轧态试样的抗剥落腐蚀能力最差,由于冷轧压下量大的样品中位错密度大,所具有的储能高,因此要产生同等程度的腐蚀,压下量大的样品所需要的退火温度比压下量小的样品所需要的退火温度要低。随着冷轧压下量的增加,再结晶形成的晶粒越小,晶粒数目越多,吕德丝带越长,锯齿的频率和振幅都越大。在单轴拉伸过程中,随着应变的增加,锯齿的频率降低,锯齿的振幅先升高后降低。经过回复退火后的样品内位错密度比冷轧态样品要小,因此锯齿的强度越小。3.在同一变形温度下,均匀化后的5A01铝合金的真应力随应变速率的增大而增大,表明5A01是正应变速率敏感材料。在同一应变速率下,5A01的真应力水平随温度的提高而降低。在相同的变形温度以及变形速率下,变形量对流变应力的影响不大。采用双曲正弦形式的Arrhenius关系来描述5A01铝合金高温变形时的流变应力,获得5A01的材料常数A、α、n和Q分别为0.06831s^-1、0.0094MPa^-1、2.7089和161.14KJ/mol。更多还原

【Abstract】 In this paper,the corrosion resistance,yielding behavior and the behavior during hot compression deformation of high Mg 5XXX aluminum alloy with different Mg content and different treatment have been studied by means of the slow strain-rate test,isothermal compression simulation test,DSC analysis,micro-hardness testing,electro-chemistry characteristic,metallographic microscope,SEM, TEM.Experimental results show:1.The low SCC resistance and intergranular corrosion resistance of the as-quenched alloy annealing at 150℃for 1 huor is relate to more and largerβphase precipitate after 150℃1 hour aging than the same Mg content alloy as-quenched or after 350℃1 hour aging.The same treatment alloy with lower Mg content has better corrosion resistance than the one with higher Mg content under the same condition.The serrated yielding intense of alloy after 150℃aging reduce when adding aging time.Low serrated yielding intense,elongation and high UTS is relate to more and largerβphase precipitate after 150℃1 hour aging than the same Mg content alloy as-quenched or after 350℃1 hour aging.2.The as cold-rolled alloy has the worst exfoliation corrosion resistance due to exist of residual stress.The precipitated temperature ofβphase reduce when increase reduction of cold-rolled treatment,which induce the different effect of heat treatment temperature to corrosion resistance of alloy.After recrystallization is completed,the smaller the recrystallized grain the longer the Luders elongation.The frequency of serrations also increases with decreasing grain size.The frequency of serrations decreases and the magnitude of serrations first increases and then decrease with increase in strain.The cold-rolled sample which has higher dislocation density has more intense serration than the sample after recovery heat treatment.3.To the 5A01 alloy after homogenization annealing:The stress increase with the strain rate at the same compression temperature,which show 5A01 aluminum alloy is positive strain rate sensitivity material,the stress increase with the compression temperature at the same strain rate. Deforming degree has little effect on the stress at the strain rate and the same compression temperature.The flow stress of 5A01 aluminum alloy during hot deformation can be expressed by Arrhenius function in the hyperbolic sine style.The values of A、α、n and Q in the analytical expression are 0.06831s^-1、0.0094MPa、2.7089 and 161.14KJ/mol.更多还原