单级时效对7B04预拉伸厚板组织和性能的影响

研究了7B04合金单级时效处理过程中时效温度和时效时间对合金力学性能和电导率的影响,观察和对比了几种不同时效处理制度下合金的显微组织.结果表明:单级时效处理的温度越高,合金达到峰时效所需的时间越短,材料的峰时效强度和延伸率越低.电导率随时效时间的延长而不断上升;时效温度越高,电导率的增长速率越快.峰时效合金基体内有大量细小的弥散相析出,晶界析出相呈连续分布.当时效温度较低时,过时效合金的显微组织与峰时效没有明显差别;当时效温度较高时,过时效合金内粗大析出相的数量明显增加,晶界析出相呈不连续分布.不同时效温度下的峰时效和过时效合金中均不存在明显的晶间无析出带.     

7A04R铝合金管件开裂原因分析

用户采用我公司的φ125 mm×25 mm7A04R铝台金管材生产管件,在检查时发现个别管件的侧面存在开裂现象.通过对缺陷进行宏观组织和显微组织的观察及分析得知:此开裂缺陷是由于用户热处理不当造成的,是过烧引起的淬火裂纹.     

热处理对7B04铝合金厚板组织与力学性能的影响

通过显微组织观察和力学性能与电导率测试,研究了热处理工艺对7B04铝合金厚板组织与性能的影响。结果表明,适宜的固溶工艺为470℃×240min。120℃×22h时效后合金可获得,抗拉强度为621MPa,但合金的电导率较低,仅为18·3MS/m;双级T74时效时,强度下降了10%～12%(与T6态相比),电导率获得了明显提高,为21·3MS/m;三级时效(RRA)处理可使合金获得高强度和高电导率相结合,强度接近T6态,电导率与T74态相当。合金经RRA处理后,基体内分布着大量的细小弥散析出相(与T6态组织相似),晶界析出相粗大且呈完全不连续分布。     

7A04铝合金超厚板的淬透性

采用万能力学试验机、光学显微镜、扫描电镜等手段,研究了7A04铝合金超厚板的显微组织、性能及淬透性。结果表明:225 mm厚的7A04铝合金热轧板材经过475 ℃×340 min的固溶淬火处理后,再进行120 ℃×24 h 时效,其表面的力学性能最好,抗拉强度为584 MPa,屈服强度为500 MPa,伸长率为11%;T/4厚度层力学性能最差,抗拉强度为396 MPa,屈服强度为257 MPa,伸长率为11%,强度与表面分别相差32%、49%。淬透深度为单面32 mm。通过调控化学成分、加大轧制压下量、增加淬火冷却速率等可改善板材表心力学性能之差,并提高淬透性。     

7B04-T6铝合金挤压型材热处理

对7B04-T6合金型材热处理制度进行深入研究,制定出合理的工艺制度,使其生产出的T6状态型材的各项性能均能达到指标要求.     

时效制度对7B04铝合金组织和性能的影响

通过力学性能检测、扫描电镜和透射电镜观察,研究了不同时效制度、不同变形系数对7B04铝合金组织和性能的影响.结果表明:变形系数为12.5的合金其性能优于变形系数为6.5的合金;合金的断裂属晶内韧窝断裂与沿晶断裂的混合型断裂,合金的K IC主要受其δ值的影响并与其δ值有相似的变化趋势;合金的完全时效制度为130℃,16 h或140℃,15 h,在此制度下,合金的σb,σ0.2,δ和K IC分别为645.5 MPa,603.0 MPa,11.4%和36.1 MPa·mi/2.     

直流电对7B04铝合金固溶与时效组织和性能的影响

本文采用拉伸试验、扫描电子显微镜(SEM)和透射电子显微镜(TEM)等手段,研究了7B04铝合金在施加和不施加直流电条件下,经470℃固溶和100-140℃时效处理后的组织和力学性能。与传统的T6处理(470 oC/30 min+120 oC/24h)相比,固溶和/或时效处理时施加500A的电流,可显著提高GPII区的析出密度,进而提高峰时效状态下的拉伸强度和延伸率。固溶过程中施加直流电可将随后时效合金达到峰值强度的时间明显缩短12h。     

7B04-T6铝合金型材黑色条纹的原因分析

通过对7B04-T6铝合金DQ2544型材外观形貌、断口组织特征、显微组织特征、扫描电镜特征等几方面进行系统地观察,并结合生产工艺的特点,找出7B04-T6铝合金型材黑色条纹产生的原因,对其形成机制进行了阐述,为改善产品质量提供了依据,提出了避免该缺陷的方法。     

7B04铝合金疲劳断裂性能研究

研究了新型的7B04铝合金预拉伸厚板不同热处理状态的断裂韧性和疲劳裂纹扩展性能变化,试验结果表明,该合金T7451状态的断裂韧性和疲劳裂纹扩展性能明显优于T651状态的性能。     

二级时效温度对7B04-T74铝合金薄板组织及性能的影响

采用光学显微镜、透射电镜组织分析手段和室温拉伸、电导率、剥落腐蚀、疲劳极限性能测试方法,研究了二级时效温度对7B04-T74合金2 mm厚薄板组织与性能的影响。结果表明:二级时效温度由165 ℃逐渐升高至175 ℃时,7B04-T74合金晶粒组织特征没有明显变化,晶内析出相数量减少且尺寸增加,晶界析出相粗大且断续分布;7B04-T74态铝合金薄板的室温拉伸抗拉强度、屈服强度明显降低,其伸长率无明显变化,电导率明显提升,剥落腐蚀级别无明显变化趋势。通过对比不同二级时效温度下7B04铝合金的组织与性能测试结果可知,7B04合金2 mm厚薄板由退火状态到T74状态的最优二级时效温度为173 ℃。     

Effect of homogenization treatment on microstructure and hot workability of high strength 7B04 aluminium alloy

The effects of homogenization treatment on microstructure, overbumt temperature and hot rolling plasticity of high strength 7B04 aluminium alloy were investigated. Under the condition of homogenization at 470 ℃, the starting melting temperature of the primary eutectics in ingot of non-equilibium solidified 7B04 alloy is 478 ℃. Using two-step homogenization processing at ultra-high temperature which comprises heating the ingots to 470 ℃ at 10 ℃/h and holding for 64 h, and then heating to 500 ℃ at 1 ℃/h and holding for 10 h, the ingots of 7B04 aluminium alloy could safely pass the sensitive overbumt zone between 480 ℃ and 495 ℃, and the ordinary burnt phenomena of the ingots between 480 ℃ and 495 ℃ does not occur because the excess low-melting point eutectic phases in the as-cast alloy dissolve into the matrix during the two-step homogenization processing. Consequently, the hot rolling plasticity of ingot of 7B04 aluminium alloy is greatly improved.     

Microstructural evolution of aluminum alloy 7B04 thick plate by various thermal treatments

The microstructure of an AA 7B04 alloy in the form of plate was investigated using differential scanning calorimetry （DSC） and TEM analysis technologies. Tensile properties and electrical conductivity of AA 7B04 under various heat treatment conditions were also presented. The results reveal that peak-aged microstructure contains GP zones and η＇ precipitates predominantly. After retrogressing and reaging（RRA）, the η＇ and η precipitates disperse in the alloy matrix, and the η precipitates distribute coarsely and sparsely, decorating the grain boundaries, together with precipitate free zones（PFZs） around them. It is also shown that selecting of suitable heat treatments can provide optimal precipitates in matrix and at grain boundaries, which gives rise to a combination of high strength and stress corrosion cracking（SCC） resistance in such materials.     

Overheating temperature of 7B04 high strength aluminum alloy

The microstructure and overheating characteristics of the direct chill semicontinuous casting ingot of 7B04 high strength aluminum alloy, and those after industrial homogenization treatment and multi-stage homogenization treatments, were studied by differential scanning calorimetry(DSC), optical microscopy(OM) and scanning electron microscopy with energy dispersive X-ray spectroscopy(SEM-EDX). The results show that the microstructure of direct chill semicontinuous casting ingot of the 7B04 alloy contains a large number of constituents in the form of dendritic networks that consist of nonequilibrium eutectic and Fe-containing phases. The nonequilibrium eutectic contains Al, Zn, Mg and Cu, and the Fe-containing phases include two kinds of phases, one containing Al, Fe, Mn and Cu, and the other having Al, Fe, Mn, Cr, Si and Cu. The melting point of the nonequilibrium eutectic is 478 ℃ for the casting ingot of the 7B04 alloy which is usually considered as its overheating temperature. During industrial homogenization treatment processing at 470 ℃, the nonequilibrium eutectic dissolves into the matrix of this alloy partly, and the remainder transforms into Al2CuMg phase that cannot be dissolved into the matrix at that temperature completely. The melting point of the Al2CuMg phase which can dissolve into the matrix completely by slow heating is about 490 ℃. The overheating temperature of this high strength aluminum alloy can rise to 500-520 ℃. By means of special multi-stage homogenization, the temperature of the homogenization treatment of the ingot of the 7B04 high strength aluminum alloy can reach 500 ℃ without overheating.     

单级时效对7804预拉伸厚板组织和性能的影响

研究了7804合金单级时效处理过程中时效温度和时效时间对合金力学性能和电导率的影响，观察和对比了几种不同时效处理制度下合金的显微组织。结果表明：单级时效处理的温度越高，合金达到峰时效所需的时间越短，材料的峰时效强度和延伸率越低。电导率随时效时间的延长而不断上升；时效温度越高，电导率的增长速率越快。峰时效合金基体内有大量细小的弥散相析出，晶界析出相呈连续分布。当时效温度较低时，过时效合金的显微组织与峰时效没有明显差别；当时效温度较高时，过时效合金内粗大析出相的数量明显增加，晶界析出相呈不连续分布。不同时效温度下的峰时效和过时效合金中均不存在明显的晶间无析出带。     

基于简化辊系模型的热轧宽厚板板形有限元分析方法

建立基于简化辊系模型的热轧有限元模型及基于解析算法的工作辊弹性压扁模型,通过模型间的迭代计算,获得了最终稳定的板形。基于Windows平台,将该方法用C#语言开发成一套板形分析计算软件。该计算软件综合有限元法与解析算法的优点,实现了板形的快速计算以及对板形因素的定量分析。     

7B04铝合金的时效沉淀析出及强化行为

利用差示量热法(DSC)、透射电镜(TEM)、选区电子衍射(SAED)、常规力学性能测试等手段研究了7B04铝合金时效沉淀析出及强化行为。结果表明:该材料存在显著的自然时效现象,大量的GPⅠ区沉淀析出是自然时效强化的主要原因;合金在120℃进行人工时效的初期析出大量GP区,使材料的强度迅速提高,时效8 h后,其横向极限抗拉强度即可达到570 MPa,时效22 h时可达强度峰值点,此时GP区(包括GPⅠ和GPⅡ区)和η′相是主要强化相;峰值时效后继续延长时效时间,材料的强度无明显降低,极限抗拉强度保持在590 MPa左右。