简介概要

均匀化对7050铝合金板材淬火敏感性的影响

来源期刊:中国有色金属学报2010年第6期

论文作者:刘文军 张新明 刘胜胆 周新伟

文章页码:1102 - 1109

关键词:7050铝合金;均匀化制度;Al3Zr;淬火敏感性;组织演变

Key words:7050 aluminum alloy; homogenization treatment; Al3Zr; quenching sensitivity; microstructure evolution

摘    要:通过光学显微镜、透射电镜以及力学性能测试,研究均匀化制度对7050铝合金板材组织演变的影响。将合金固溶后在不同速率淬火,研究均匀化制度对该合金淬火敏感性的影响。结果表明:固溶后慢速率淬火过程中,平衡相η主要位于再结晶晶粒中Al3Zr粒子的相界、再结晶晶界、亚晶晶界以及亚晶中与位错交互作用的少量Al3Zr粒子上形核析出;均匀化时间较短时(室温,120 ℃/h升温至465 ℃,8 h),合金中析出少量Al3Zr粒子,固溶后的试样发生完全再结晶,此时合金淬火敏感性最好,但硬度较低;延长保温时间至20 h(室温,120 ℃/h升温至465 ℃,20 h),试样中析出大量Al3Zr粒子,但分布不均匀,从而导致轧制固溶后的试样依然明显再结晶,合金淬火敏感性较差;采用快速升温的双级均匀化制度((室温,120 ℃/h升温至465 ℃,20 h)+(475 ℃,8 h)),Al3Zr粒子有所长大,淬火敏感性最差;采用慢速随炉升温((室温,18 ℃/h升温至465 ℃)+(475 ℃,8 h))的双级均匀化制度,合金中将弥散析出大量细小的Al3Zr粒子,固溶后的再结晶得到有效抑制,较多η相在亚晶界上的非均匀形核析出在一定程度上增加了合金的淬火敏感性,但该制度处理的合金仍优于再结晶程度较高的快速升温双级均匀化制度的。

Abstract: The microstructure evolution of 7050 aluminum alloy plates after homogenization was studied by optical microscopy, transmission electron microscopy, hardness and electric conductivity measurements. The influence of such processing on the quenching sensitivity was investigated by different homogenization methods. The results show that the equilibrium η phase mainly precipitates at areas such as the grain boundaries, sub-grain boundaries, incoherent Al3Zr particles within the recrystallization region and some Al3Zr particles which interact with the dislocations during slow quenching. For short time homogenization treatment (RT, 120 ℃/h to 465 ℃, 8 h), the recrystallization is observed at most of the areas and the alloy shows good quenching sensitivity but low hardness. When the holding time increases to 20 h (RT, 120 ℃/h to 465 ℃, 20 h), the recrystallization would be partly inhibited with higher quenching sensitivity. The two-stage homogenization with fast heating rate ((RT, 120 ℃/h to 465 ℃, 20 h)+(475 ℃, 8 h)) can not improve the quenching sensitivity and the Al3Zr particles coarsen slightly. And when the ramp heating (RT, 18 ℃/h to 465 ℃+ 475 ℃, 8h) is concerned, the recrystallization is inhibited efficiently by finer size and higher density of Al3Zr particles,and the equilibrium η phase mainly precipitates at the sub-grain boundaries and some Al3Zr particles interact with the dislocations, in addition better quenching sensitivity is achieved.

基金信息:国家重点基础研究发展计划资助项目



详情信息展示

文章编号:1004-0609(2010)06-1102-08

均匀化对7050铝合金板材淬火敏感性的影响

刘文军,张新明,刘胜胆,周新伟

(中南大学 材料科学与工程学院,长沙 410083)

摘  要:通过光学显微镜、透射电镜以及力学性能测试,研究均匀化制度对7050铝合金板材组织演变的影响。将合金固溶后在不同速率淬火,研究均匀化制度对该合金淬火敏感性的影响。结果表明:固溶后慢速率淬火过程中,平衡相η主要位于再结晶晶粒中Al3Zr粒子的相界、再结晶晶界、亚晶晶界以及亚晶中与位错交互作用的少量Al3Zr粒子上形核析出;均匀化时间较短时(室温,120 ℃/h升温至465 ℃,8 h),合金中析出少量Al3Zr粒子,固溶后的试样发生完全再结晶,此时合金淬火敏感性最好,但硬度较低;延长保温时间至20 h(室温,120 ℃/h升温至465 ℃,20 h),试样中析出大量Al3Zr粒子,但分布不均匀,从而导致轧制固溶后的试样依然明显再结晶,合金淬火敏感性较差;采用快速升温的双级均匀化制度((室温,120 ℃/h升温至465 ℃,20 h)+(475 ℃,8 h)),Al3Zr粒子有所长大,淬火敏感性最差;采用慢速随炉升温((室温,18 ℃/h升温至465 ℃)+(475 ℃,8 h))的双级均匀化制度,合金中将弥散析出大量细小的Al3Zr粒子,固溶后的再结晶得到有效抑制,较多η相在亚晶界上的非均匀形核析出在一定程度上增加了合金的淬火敏感性,但该制度处理的合金仍优于再结晶程度较高的快速升温双级均匀化制度的。

关键词:7050铝合金;均匀化制度;Al3Zr;淬火敏感性;组织演变

中图法分类号:TG146       文献标志码:A

Effect of homogenization on quenching sensitivity

of 7050 aluminum alloy plates

LIU Wen-jun, ZHANG Xin-ming, LIU Sheng-dan, ZHOU Xin-wei

(School of Materials Science and Engineering, Central South University, Changsha 410083, China)

Abstract: The microstructure evolution of 7050 aluminum alloy plates after homogenization was studied by optical microscopy, transmission electron microscopy, hardness and electric conductivity measurements. The influence of such processing on the quenching sensitivity was investigated by different homogenization methods. The results show that the equilibrium η phase mainly precipitates at areas such as the grain boundaries, sub-grain boundaries, incoherent Al3Zr particles within the recrystallization region and some Al3Zr particles which interact with the dislocations during slow quenching. For short time homogenization treatment (RT, 120 ℃/h to 465 ℃, 8 h), the recrystallization is observed at most of the areas and the alloy shows good quenching sensitivity but low hardness. When the holding time increases to 20 h (RT, 120 ℃/h to 465 ℃, 20 h), the recrystallization would be partly inhibited with higher quenching sensitivity. The two-stage homogenization with fast heating rate ((RT, 120 ℃/h to 465 ℃, 20 h)+(475 ℃, 8 h)) can not improve the quenching sensitivity and the Al3Zr particles coarsen slightly. And when the ramp heating (RT, 18 ℃/h to 465 ℃+   475 ℃, 8h) is concerned, the recrystallization is inhibited efficiently by finer size and higher density of Al3Zr particles,and the equilibrium η phase mainly precipitates at the sub-grain boundaries and some Al3Zr particles interact with the dislocations, in addition better quenching sensitivity is achieved.

Key words: 7050 aluminum alloy; homogenization treatment; Al3Zr; quenching sensitivity; microstructure evolution

 



7×××系铝合金作为综合性能优秀的航空航天材料已被广泛应用,国内外对该系合金的开发和研究也一直没有停止[1-5]。早在20世纪80年代初,Thompson等[6]就已指出Al-Zn-Mg-Cu系铝合金中微量添加的Cr和Zr等元素将导致合金慢速率淬火时性能受到损失,淬火时η平衡相 (MgZn2)的非均匀形核析出是造成合金淬火敏感性较大的直接原因[6-11],DESCHAMPS  等[13-14]在前人的基础上进一步研究了合金中含Zr粒子的分布对6×××系和7×××系铝合金淬火敏感性的影响,认为慢速率淬火时η平衡相主要在Al3Zr粒子上形核析出,与Al3Zr粒子一起呈带状分布,另有报道指出,再结晶晶粒中与基体非共格的Al3Zr粒子是η相非均匀形核的主要位置[15-16]。在已有的研究中,关于热处理制度对合金淬火敏感性影响的文献相对较少,尤其关于均匀化制度对合金淬火敏感性的影响未见报道;固溶后慢速率淬火时,亚晶组织中的η平衡相的析出行为鲜见报道。因此,本文作者从均匀化角度出发,分析均匀化制度对合金固溶后慢速率淬火时η平衡相析出行为影响,阐明其与合金淬火敏感性的联系,具有理论价值,同时为实际生产中的均匀化制度选择提供参考依据。

1  实验

实验用7050铝合金的铸锭名义成分如表1所列。铸锭上切取厚12 mm的试样于空气炉中进行4种均匀化热处理,分别为快速升温的单级均匀化制度(室温,120 ℃/h升温至465 ℃,8 h);在保温8 h基础上延长保温时间20 h,即(室温,120 ℃/h至465 ℃,20 h);在单级制度基础上增加二级保温的快速升温双级均匀化制度(室温,(120 ℃/h升温至465 ℃,20 h)+(475 ℃,8 h));以及采用慢速率升温的双级均匀化(室温,(18 ℃/h升温至465 ℃)+(475 ℃,8 h))。为表述方便,4种均匀化制度分别用制度a、b、c和d表示。对均匀化后水淬样品立即制备透射试样进行微观组织观察;随后对样品进行统一轧制制度的热变形处理(开轧温度420 ℃,总轧制变形量85%,并严格控制轧制道次和每道次变形量,减少轧制制度不同造成的储能差异);固溶处理在空气炉中进行(固溶制度472 ℃,60 min),随后采用空气和室温水两种介质进行淬火处理(通过比较空气淬火试样时效后性能损失反映合金淬火敏感性差异),实测淬火速率分别为1和300 ℃/s左右,淬火试样进行电导率测定后立刻置于油浴炉中进行时效(121 ℃,24 h);最后对时效态试样分别进行电导率、硬度测试,并结合金相和TEM对样品进行组织观察,分析实验结果。

表1  7050铝合金的名义成分

Table 1 Nominal composition of Al 7050 alloy in present study (mass fraction, %)

实验中所采用的主要设备如下:XJP-6A 型光学显微镜,TecnaiG220透射电镜以及HV10-B硬度测试仪,TEM试样采用双喷减薄制备,双喷电解液配比为20%(体积分数)HNO3+80%CH3OH,温度控制在-20 ℃以下。

2  实验结果

2.1  合金的组织形貌

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