Al-Mg-Si-Zr-XEr合金组织性能及时效析出强化的研究

发布时间：2018-01-17 21:38

本文关键词：Al-Mg-Si-Zr-XEr合金组织性能及时效析出强化的研究　出处：《沈阳工业大学》2016年博士论文　论文类型：学位论文

【摘要】：近些年,汽车产业蓬勃发展,Al-Mg-Si合金在汽车工业上的研究和应用也备受关注。微合金化是改善合金力学性能的有效方式,微量合金化元素对合金产生两方面作用,一是异质形核细化晶粒,再者影响合金析出相的时效析出进而提高性能。本文在6111合金成分基础上,通过微合金化Er、Zr元素的方式,配制了成分为Al-0.8Mg-1.0Si-0.8Cu-0.2Mn-0.15Zr-(0.1、0.2、0.3) Er的不同Er元素含量铝合金。通过对不同Er元素含量Al-Mg-Si-Zr-Er合金组织、性能、织构,以及含Er元素0.3%铝合金的热处理工艺、析出行为和强化机理的研究,奠定了Er元素微合金化应用的理论基础,获得了一种综合性能较好的Al-0.8Mg-1.0Si-0.8Cu-0.2Mn-0.15Zr-0.3Er合金。Al-Mg-Si-Cu-Mn-Zr-Er合金铸态组织为枝晶和等轴晶混合形态,第二相主要为CuAl2、Al3Zr、Al1.9CuMg4.1Si3.3 (Q相)、Al3Er、Al4Mn3Si2、Mg2Si和β-Si相。经过均匀化退火后,组织变得更加均匀,低熔点Al1.9CuMg4.1Si3.3 (Q相)、CuAl2相和Mg2Si相消失,Er、Zr元素与Al元素形成了三元核壳状Al3(Er,Zr)复合相。合金挤压态组织沿挤压方向晶粒被延伸,在晶粒内部及晶界处存在大量的析出相聚集区,呈现一定的方向性分布。合金轧制态组织为纤维组织,纤维层间距小且模糊,合金晶粒变的细而长,沿轧制的方向表现出明显的方向性,析出相在轧制过程中被压碎。T6热处理后的合金板材组织为等轴晶,低熔点溶质原子从过饱和基体内析出。采用Er元素微合金化时,随Er元素含量的增加,铸态、挤压态、轧制态和热处理态Al-Mg-Si-Cu-Mn-Zr-Er合金组织均有逐渐细化的倾向,强度和硬度均提高,但合金塑性减弱效果并不明显。时效过程中,随Er元素含量的增加,合金到达峰值硬度的时间明显缩短。T6热处理后,含Er元素0.3%的铝合金,其再结晶组织细化明显,板材晶界处的析出物也逐渐增多,溶质原子析出更充分,综合力学性能良好。在不同取向条件下,含Er元素0.1%的合金力学性能差异性较大,随着Er元素含量增加,合金板材力学性能差异性降低,含Er元素0.3%的合金三项IPA值为0.39%、1.59%、0.77%。在Al-Mg-Si-Cu-Mn-Zr-Er合金织构的研究上,合金轧制后织构主要为旋转立方织构{100}011,黄铜R织构{111}110和{111}112,常规变形织构B、S、C织构很弱。随着Er元素含量增加,织构体积分数下降,随机组分增多,制耳率有下降的趋势。微量Er元素的加入引起基体晶格变化,降低铝合金的层错能,阻碍了交滑移的进行,造成织构含量的转变。固溶处理后,含Er元素0.1%的Al-Mg-Si-Cu-Mn-Zr-Er合金中,主要织构是黄铜织构和旋转立方织构Cube+ND25, PSN形核是含Er元素0.1%铝合金的再结晶形核机制之一；Er元素含量增加到0.2%、0.3%时,织构为较弱的黄铜织构,PSN形核减弱。Al-0.8Mg-1.OSi-0.8Cu-0.2Mn-0.15Zr-0.3Er合金的T4、T4P和T6热处理工艺的研究表明,Al-0.8Mg-1.0Si-0.8Cu-0.2Mn-0.15Zr-0.3Er合金在自然时效1.5d和4d时,烤漆前后的强度、硬度均呈双峰特征。经T4处理后的Al-0.8Mg-1.0Si-0.8Cu-0.2Mn-0.15Zr-0.3Er合金模拟烤漆时,硬化速度减慢,p”相的析出被延迟,烤漆后形成的是以β"核心为主的析出物,出现烤漆软化效应；而经过预时效、自然时效处理(T4P)后的合金进行模拟烤漆时,形成的析出相以p”相为主,实现了板材烤漆强化,延长预时效时间,烤漆硬化效果进一步提高。Al-0.8Mg-1.0Si-0.8Cu-0.2Mn-0.15Zr-0.3Er合金的T6峰时效工艺为：540℃固溶1h,180℃时效时间5h,峰时效抗拉强度和屈服强度达到了392.4MPa和321.8MPa,伸长率为24.32%,硬度达到了117HB。考虑到汽车板材对合金冲压性能的要求,较合理的预时效工艺为固溶淬火处理后立即进行170℃/5min预时效,然后成型件通过自然时效和烤漆工艺进一步提高力学性能。在合金的时效析出行为与强化机理的研究上,Er和Zr元素的加入促进了Al-Mg-Si-Cu-Mn-Zr-Er合金主强化相β"相的析出,β"相析出温度变低,β"相也更为细小弥散,缩短了Al-Mg-Si-Cu-Mn-Zr-Er合金自然时效达到第一峰值的时间和合金达到峰时效时间。随Er元素含量的增加,Al-Mg-Si-Cu-Mn-Zr-Er合金β"相析出激活能降低,分别为96.3、93.6和84.9kJ/mol。析出动力学方程分别为：YEro.i=l-exp[-1.534×1013t1.5exp (-17382.7/T)]、YE0.2=1-expt[-5.268×1012t1.5exp(-16895.3/T)]、YEr0.3=[-2.965×1011 t1.5exp(-15324.9/T)];, Al-Mg-Si-Cu-Mn-Zr-Er合金β"相TTT表达式分别为：TEr0.1=17382.7/[30.4+1.51nt-lnln(1-Y)-1]、TEr0.2=16895.3/[29.4+1.51nt-lnln(1-Y)-1] TEr0.3=15324.9/[26.4+1.51nt-lnln(1-Y)-1]。Er和Zr元素的加入对,Al-Mg-Si-Cu-Mn-Zr-Er合金的强化起到了较大贡献。合金强化可归纳为加工硬化、细晶强化、固溶强化和第二相强化,其中,第二相强化又包含弥散强化和沉淀强化,第二相强化机制为Orowan绕过强化机制。
[Abstract]:In recent years, vigorous development of automobile industry, the research and application of Al-Mg-Si alloy in automobile industry is also of concern. Micro alloying is an effective way to improve the mechanical properties of the alloy, alloying elements have two effects on the alloy, is a heterogeneous nucleation of grain refinement, and effect of alloy precipitates aging and improve the performance. In this paper based on the 6111 component alloy, through micro alloying elements Er, Zr, compound composition of Al-0.8Mg-1.0Si-0.8Cu-0.2Mn-0.15Zr- (0.1,0.2,0.3) with different content of Er Aluminum Alloy Er. According to the organization, with different content of Er texture and properties of Al-Mg-Si-Zr-Er alloy, Er element containing 0.3% Aluminum Alloy heat treatment process, the study of the precipitation the behavior and strengthening mechanism, lay a theoretical foundation for application of microalloying element Er, obtained a better comprehensive performance Al-0.8Mg-1.0Si-0.8Cu-0.2Mn-0.15 Zr-0.3Er alloy as cast.Al-Mg-Si-Cu-Mn-Zr-Er alloy for dendrite and equiaxed mixed form, mainly for the second phase of CuAl2, Al3Zr, Al1.9CuMg4.1Si3.3 (Q), Al3Er, Al4Mn3Si2, Mg2Si and beta -Si. After homogenization, the organization becomes more uniform, low melting point Al1.9CuMg4.1Si3.3 (Q), CuAl2 and Mg2Si Er, Zr disappeared, and Al elements formed three core-shell Al3 (Er, Zr). The microstructure of composite alloy extruded along the extrusion direction of grain was extended, inside the grains and at grain boundaries in the existence of a large number of precipitation gathered area, is now a directional distribution of rolled alloy fiber tissue. Tissue, fiber spacing is small and fuzzy, grain becomes thin and long, along the rolling direction shows obvious direction, precipitates in the rolling process was crushed after heat treatment.T6 alloy microstructure to equiaxed crystal, the low melting point of solute atoms from overeating And the matrix precipitation. Using Er micro alloying elements, with the increase of Er content, casting, extrusion, rolling and heat treatment have the tendency of Al-Mg-Si-Cu-Mn-Zr-Er alloy microstructure refinement, strength and hardness were increased, but the plasticity of the alloy. The effect is not obvious. During the aging process, with the increase of Er elements the content of the alloy significantly shorten the time to reach the peak hardness of.T6 after heat treatment, Aluminum Alloy containing Er element 0.3%, the recrystallization microstructure obviously, grain boundary precipitates plate has gradually increased, the solute atoms precipitated more fully, good mechanical properties. In different orientation conditions, Er element containing 0.1% difference the mechanical properties of the alloy is larger, with the increase of Er content, mechanical properties of alloy sheet difference decreased, Er alloy containing 0.3% elements of three IPA was 0.39%, 1.59%, 0.77%. on the texture of Al-Mg-Si-Cu-Mn-Zr-Er alloy. After the main alloy rolling texture, rotated cube texture {100}011, brass R texture {111}110 and {111}112, S, B of conventional texture, C texture is very weak. With the increase of Er content, decreased texture volume fraction, random components increase, earing rate decreased. Trace Er element added by matrix lattice change, reduce Aluminum Alloy SFE, hindered the cross slide, caused by changes in texture content. After solution treatment, Al-Mg-Si-Cu-Mn-Zr-Er alloy containing Er element 0.1%, main texture is brass texture and rotated cube texture Cube+ND25, PSN nucleation is Er element containing 0.1% Aluminum Alloy of recrystallization nucleation mechanism; the content of Er increased to 0.2%, 0.3%, for the weak texture of brass texture, PSN nucleation weakened.Al-0.8Mg-1.OSi-0.8Cu-0.2Mn-0.15Zr-0.3Er alloy T4, T4P and T6 heat treatment showed that Al-0.8Mg-1.0Si-0.8Cu-0.2Mn -0.15Zr-0.3Er alloy in the natural aging 1.5D and 4D, before and after baking strength, hardness were characteristic of Shuangfeng. After Al-0.8Mg-1.0Si-0.8Cu-0.2Mn-0.15Zr-0.3Er T4 treated alloy simulated paint, hardening rate, P phase is delayed after the formation of the paint is "beta precipitates core, paint softening effect and appearance; after pre aging, natural aging treatment (T4P) alloy after simulated paint, the formation of precipitates in P phase, the paint sheet strengthened, prolonged pre aging time, baking hardening effect and further improve the T6 peak aging process of.Al-0.8Mg-1.0Si-0.8Cu-0.2Mn-0.15Zr-0.3Er alloy is 540 DEG 1h in solution, 180 ageing the time of peak aging 5h, the tensile strength and yield strength reached 392.4MPa and 321.8MPa, the elongation is 24.32%, the hardness reached 117HB. considering the car plate on the stamping properties of the alloy. Requirements of pre aging process is reasonable for 170 DEG /5min pre aging solution immediately after quenching, then molded by natural aging and baking process to further improve the mechanical properties. In the study on aging precipitation behavior of the alloy and strengthening mechanism, Er and addition of Zr promoted Al-Mg-Si-Cu-Mn-Zr-Er alloy main strengthening phase beta "the precipitation of beta" phase precipitation temperature becomes lower, beta "phase is more dispersed, shorten the natural aging Al-Mg-Si-Cu-Mn-Zr-Er alloy alloy for the first time and reached the peak peak time. With the increase of Er content of Al-Mg-Si-Cu-Mn-Zr-Er alloy" phase precipitation decreasing the activation energy were 96.3,93.6 and 84.9kJ/mol. precipitation kinetics equation respectively: YEro.i=l-exp[-1.534 * 1013t1.5exp (-17382.7/T)], YE0.2=1-expt[-5.268 * 1012t1.5exp (-16895.3/T)], 1011 YEr0.3=[-2.965 * t1.5exp (-15324.9/T)]; Al-Mg-Si-Cu-Mn-Zr-Er alloy, beta "phase TTT expressions were as follows: TEr0.1=17382.7/[30.4+1.51nt-lnln (1-Y) -1], TEr0.2=16895.3/[29.4+1.51nt-lnln (1-Y) -1] TEr0.3=15324.9/[26.4+1.51nt-lnln (1-Y) -1].Er and Zr element was added to Al-Mg-Si-Cu-Mn-Zr-Er alloy, strengthening plays a bigger contribution. Alloy strengthening can be summarized as the hardening of fine grain strengthening, solid solution strengthening and second phase strengthening. The second phase strengthening and dispersion strengthening and precipitation strengthening, second phase strengthening mechanism for Orowan around the strengthening mechanism.

【学位授予单位】：沈阳工业大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：TG146.21

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