Mg-TM-RE系镁合金中LPSO相的研究进展

镁合金是最具发展潜力的轻量化材料之一,但相对较低的强度和塑性限制了其工程应用。具有堆垛有序和化学有序特征的长周期堆垛有序(LPSO)相是有望实现镁合金强韧化的新型析出相,受到了越来越广泛的关注。本文总结分析了LPSO相的原子结构特征、形成和转变机制,讨论了不同合金元素对LPSO相稳定性、本征结构物性参数的影响规律,分析了LPSO相对镁合金动态再结晶行为和力学性能的影响机理,并总结了基于LPSO相发展高性能镁合金需解决的关键问题,以期为新型高强韧镁合金的发展提供参考。

基于机器学习的含LPSO相镁合金腐蚀

含LPSO相镁合金具备优异的综合力学性能,在轨道交通、航空航天、生物医疗等领域具有广泛的应用前景,然而其易腐蚀的特性极大制约了该类合金的广泛应用。本文聚焦机器学习辅助研究合金腐蚀这一新兴领域,首先重点概述了机器学习在合金腐蚀研究等领域的应用进展,以期通过机器学习方法构建含LPSO相镁合金腐蚀预测模型,阐明LPSO相腐蚀机理;其次系统总结了镁合金中LPSO相含量、形状、结构、分布等显微组织对合金腐蚀性能的影响,为建立准确可靠的腐蚀模型提供借鉴与理论指导。最后,讨论了机器学习在含LPSO相镁合金腐蚀领域的发展机遇和挑战,展望了其发展前景。

LPSO相调控对ECAP挤压Mg-Y-Zn-Al合金组织和力学性能的影响

针对含18R-LPSO相铸态Mg-Y-Zn系合金塑韧性差、变形后力学性能提高有限的问题,研究了固溶、铸态+ECAP挤压和固溶+ECAP对Mg-3.74Y-1Zn-0.5Al(at%)合金力学性能的影响。结果表明,固溶处理诱发18R→14H-LPSO相转变、Al(Y,Zn)相化合物颗粒破碎细化,改善了合金的塑性,但强度几乎不变。铸态+ECAP挤压导致18R-LPSO和Al(Y,Zn)相破碎,并诱发大量α-Mg晶粒发生再结晶。固溶+ECAP挤压使14H-LPSO相弯曲或扭折变形、细小Al(Y,Zn)颗粒均匀分散,仅少数α-Mg晶粒发生再结晶,其强度、塑韧性远高于铸态+ECAP挤压合金的。良好强度、塑韧性匹配的14H-LPSO相的大量形成、α-Mg基体再结晶被抑制及细小Al(Y,Zn)颗粒的均匀分散是其性能提高的主要原因。

Microstructure and damping properties of LPSO phase dominant Mg-Ni-Y and Mg-Zn-Ni-Y alloys

This work studied the microstructure,mechanical properties and damping properties of Mg_(95.34)Ni_(2)Y_(2.66) and Mg_(95.34)Zn_(1)Ni_(1)Y_(2.66)alloys systematically.The difference in the evolution of the long-period stacked ordered(LPSO)phase in the two alloys during heat treatment was the focus.The morphology of the as-cast Mg_(95.34)Ni_(2)Y_(2.66)presented a disordered network.After heat treatment at 773 K for 2 hours,the eutectic phase was integrated into the matrix,and the LPSO phase maintained the 18R structure.As Zn partially replaced Ni,the crystal grains became rounded in the cast alloy,and lamellar LPSO phases and more solid solution atoms were contained in the matrix after heat treatment of the Mg_(95.34)Zn_(1)Ni_(1)Y_(2.66)alloy.Both Zn and the heat treatment had a significant effect on damping.Obvious dislocation internal friction peaks and grain boundary internal friction peaks were found after temperature-dependent damping of the Mg_(95.34)Ni_(2)Y_(2.66)and Mg_(95.34)Zn_(1)Ni_(1)Y_(2.66)alloys.After heat treatment,the dislocation peak was significantly increased,especially in the alloy Mg_(95.34)Ni_(2)Y_(2).66.The annealed Mg_(95.34)Ni_(2)Y_(2.66)alloy with a rod-shaped LPSO phase exhibited a good damping performance of 0.14 atε=10^(−3),which was due to the difference between the second phase and solid solution atom content.These factors also affected the dynamic modulus of the alloy.The results of this study will help in further development of high-damping magnesium alloys.

基于PCC-LPSO-BP的油气管道缺陷分类识别研究

为准确识别油气管道的缺陷类型,分析缺陷漏磁信号特征对识别精度的影响,建立了基于PCC-LPSO-BP的油气管道缺陷识别模型。采用皮尔逊相关系数法(PCC)分析了缺陷漏磁信号特征量与缺陷尺寸间的相关程度,建立了混沌映射和莱维飞行改进的粒子群优化后的BP神经网络识别模型即LPSO-BP模型,采用评价指标综合比较了模型的识别效果,分析了该识别模型对各缺陷类型的识别精度以及各特征量对识别结果的影响。研究结果表明:LPSO-BP模型相较于BP模型识别精度提高了7.47%,且在现有的数据范围内对表面剥落和裂纹的识别率达到了100%。研究结果对油气管道缺陷识别量化具有一定的参考价值。

Formation and transformation of metastable LPSO building blocks clusters in Mg-Gd-Y-Zn-Zr alloys by spinodal decomposition and heterogeneous nucleation

To study the formation and transformation mechanism of long-period stacked ordered(LPSO)structures,a systematic atomic scale analysis was conducted for the structural evolution of long-period stacked ordered(LPSO)structures in the Mg-Gd-Y-Zn-Zr alloy annealed at 300℃~500℃.Various types of metastable LPSO building block clusters were found to exist in alloy structures at different temperatures,which precipitate during the solidification and homogenization process.The stability of Zn/Y clusters is explained by the first principles of density functional theory.The LPSO structure is distinguished by the arrangement of its different Zn/Y enriched LPSO structural units,which comprises local fcc stacking sequences upon a tightly packed plane.The presence of solute atoms causes local lattice distortion,thereby enabling the rearrangement of Mg atoms in the different configurations in the local lattice,and local HCP-FCC transitions occur between Mg and Zn atoms occupying the nearest neighbor positions.This finding indicates that LPSO structures can generate necessary Schockley partial dislocations on specific slip surfaces,providing direct evidence of the transition from 18R to 14H.Growth of the LPSO,devoid of any defects and non-coherent interfaces,was observed separately from other precipitated phases.As a result,the precipitation sequence of LPSO in the solidification stage was as follows:Zn/Ycluster+Mg layers→various metastable LPSO building block clusters→18R/24R LPSO;whereas the precipitation sequence of LPSO during homogenization treatment was observed to be as follows:18R LPSO→various metastable LPSO building block clusters→14H LPSO.Of these,14H LPSO was found to be the most thermodynamically stable structure.

TiO_(2)@C catalyzed hydrogen storage performance of Mg-Ni-Y alloy with LPSO and ternary eutectic structure

A designed Mg_(88.7)Ni_(6.3)Y_(5)hydrogen storage alloy containing 14H type LPSO(long-period stacking ordered)and ternary eutectic structure was prepared by regulating the alloy composition and casting.The hydrogen storage performance of the alloy was improved by adding nano-flower-like TiO_(2)@C catalyst.The decomposition of the LPSO structure during hydrogenation led to the formation of plenty of nanocrystals which provided abundant interphase boundaries and activation sites.The nanoscale TiO_(2)@C catalyst was uniformly dispersed on the surface of alloy particles,and the"hydrogen overflow''effect of TiO_(2)@C accelerated the dissociation and diffusion of hydrogen on the surface of the alloy particles.As a result,the in-situ endogenous nanocrystals of the LPSO structure decomposition and the externally added flower-like TiO_(2)@C catalyst uniformly dispersed on the surface of the nanoparticles played a synergistic catalytic role in improving the hydrogen storage performance of the Mg-based alloy.With the addition of the TiO_(2)@C catalyst,the beginning hydrogen desorption temperature was reduced to 200℃.Furthermore,the saturated hydrogen absorption capacity of the sample was 5.32 wt.%,and it reached 4.25 wt.%H_(2) in 1 min at 200℃and 30 bar.

基于LPSO-GRNN模型的螺栓松紧状态预测研究

在轴重式动态汽车衡的服役状态下,由于受到重型货车频繁的加卸载循环冲击,会导致其内部螺栓发生松弛脱落,针对这一问题,提出了一种基于莱维飞行改进粒子群算法优化的广义回归神经网络(LPSO-GRNN)的轴重式动态汽车衡螺栓松紧状态预测模型,并结合振动信号特征提取,将该模型应用于汽车衡螺栓松紧状态的预测。首先,研究并提取了螺栓不同松紧状态下输出振动信号的波形指标、峰值指标、脉冲指标、峭度指标等信号特征,并将其作为模型的共同输入特征向量;然后,采用莱维飞行提高了粒子群优化算法的寻优能力,通过产生随机步长,提高了算法的全局寻优能力,避免算法陷入局部最优值;利用改进的算法对广义回归神经网络(GRNN)的光滑因子进行了优化,得到了全局最优的光滑因子;最后,通过设计实验,分别使用广义回归神经网络(GRNN)、粒子群算法优化广义回归神经网络(PSO-GRNN)和LPSO-GRNN,以此来对螺栓松紧状态进行了预测,并将预测结果与实际情况进行了对比分析。实验结果表明:基于LPSO-GRNN建立的螺栓松紧状态预测模型,其预测准确率可达到95%。研究结果表明:该螺栓松紧状态预测模型可以有效提高汽车衡螺栓松紧预测的准确率,同时有效解决粒子群算法容易陷入局部最优收敛的问题。

18R-LPSO相的体积分数对Mg-Zn-Y合金腐蚀行为与机理的影响

通过实验设计阐明LPSO相对镁合金腐蚀行为的影响。按照形成18R-LPSO相的最小结构单元,即Zn/Y=3/4(摩尔比),设计4种不同LPSO相体积分数的Mg-Zn-Y合金,对比研究4种合金的显微组织和腐蚀行为。结果表明,合金主要含有α-Mg和18R-LPSO相,18R-LPSO相的体积分数随着Zn和Y含量的增加而增加。4种合金中18R-LPSO相的体积分数依次为16.55%、34.45%、54.24%和70.36%,18R-LPSO相的空间分布也由离散块状变为连续网络状。当LPSO相的体积分数在50%左右时,合金的耐蚀性最好,体积分数大于或小于50%都会导致合金耐蚀性能降低。

调控LPSO层片相Mg-9Gd-4Y-2Zn-0.5Zr合金的热变形行为及热塑性提升机制

以挤压态Mg-9Gd-4Y-2Zn-0.5Zr合金为研究对象,通过热处理调控出晶内不含和含层片状LPSO相的两种合金,进行了热压缩试验。结果表明,含层片状LPSO相合金热塑性更好,主要是由于层片状LPSO相的扭折及其诱发的连续动态再结晶能有效提升合金的变形协调能力。随后,对含层片状LPSO相合金的热变形行为进行了深入研究,发现在低应变速率变形时,软化机制主要以不连续动态再结晶为主。在高应变速率变形时,动态回复和不连续动态再结晶共同作用,造成材料软化。结合应变0.8下的热加工图和典型区域微观组织分析,确定最佳成形温度为440~480℃,应变速率为0.001~0.01 s-1。提出了一种通过调控层片状LPSO相提升稀土镁合金热塑性的方法,为挤压态稀土镁合金的后续变形提供了新思路。

超声振动对含LPSO结构的Mg_(98)Y_(1.0)Ni_(0.5)Al_(0.5)合金显微组织与力学性能的影响

低Y、Ni含量的LPSO结构增强镁合金具有低成本、优异力学性能的特点。为进一步提升其综合力学性能,掺杂Al元素及熔体超声振动处理是可行的途径。通过扫描电子显微镜、能谱分析、透射电子显微镜、X射线衍射和纳米压痕测试研究掺杂Al元素后低Y、Ni含量的Mg_(98)Y_(1.0)Ni_(0.5)Al_(0.5)合金的显微组织,对比超声振动对显微组织与力学性能的影响。掺杂Al后LPSO结构的含量降低,且在块状LPSO结构相邻处析出圆整的Al_(2)NiY相。Al_(2)NiY相与LPSO结构和Mg基体在界面处均不共格。通过对熔体施加超声振动处理后,Al_(2)NiY相被有效细化为短片状,并均匀分布在基体中,阻碍微裂纹的产生和扩展,从而提高Mg98Ni0.5Y1.0Al0.5合金的力学性能。与未经超声处理Mg_(98)Ni_(0.5)Y_(1.0)Al_(0.5)合金相比,其极限抗拉强度和伸长率提升至187 MPa和7.9%,分别增长21.4%和105.7%。

Dissolution and reprecipitation of 14H-LPSO structure accompanied by dynamic recrystallization in hot-extruded Mg_(89)Y_(4)Zn_(2)Li_(5) alloy

We investigate the variation induced in long-period stacking ordered(LPSO)structures,dynamic recrystallization(DRX),and mechanical performance of hot-extruded Mg89Y4Zn2Li5 alloys fabricated at different extrusion speeds(Ve=0.4,0.8,1.0,1.2 mm/s)and die angles(α=30°,60°,90°)under 400℃,the dissolution and reprecipitation of 14H LPSO structure accompanied by DRX process are then clarified in detail.Upon all extrusion conditions,the block 18R LPSO structures elongate in the extrusion direction,while the lamellar 14H LPSO structures dissolve under the deformation strain.In addition,due to discontinuous and continuous DRX mechanisms,all hot-extruded alloys have a full DRX microstructure consisting of equiaxed recrystallized grains,but the DRX grain size reduces when both extrusion speed and die angle decrease.Note that,in the interior of DRX grains,thin LPSO lamellae mixing 14H,18R and 24R structures nucleate and dynamically precipitate due to the dissolution of the original lamellar 14H LPSO structures.Furthermore,the hot-extruded Mg_(89)Y_(4)Zn_(2)Li_(5)alloy becomes stronger as decreasing of the extrusion speed and die angle,whereas the ductility remains nearly constant.Finally,the hotextruded Mg_(89)Y_(4)Zn_(2)Li_(5)alloy achieves an excellent strength-ductility balance at a relatively low extrusion speed(0.4 mm/s)and small die angle(30°)mainly due to the elongated 18R LPSO structure,fine and full DRX microstructure,thin mixed LPSO precipitates in the DRX grains,twins and dislocations.

Synergetic deformation mechanisms in an Mg-Zn-Y-Zr alloy with intragranular LPSO structures

Deformation kink is one of the important strengthening mechanisms of the long-period-stacking-ordered(LPSO)phase containing magnesium(Mg)alloys,while the deformation twin is generally suppressed.To optimize the mechanical properties of LPSO containing Mg alloy by simultaneously exciting kink and twin,we successfully prepared the Mg-Zn-Y-Zr alloy featuring intragranular LPSO phase and free grain boundary LPSO phase by homogenization.We unraveled the corresponding strengthening and toughening mechanisms through transmission electron microscopy characterization and theoretical analysis.The high strength and good plasticity of the homogenized alloy benefit from the synergistic deformation mechanism of multiple kinking and twining in the grains.And the activation of kinking and twinning depends on the thicknesses of LPSO lamellae and their relative spacing.These results may shed light on optimizing the design of Mg alloys regulating the microstructure of LPSO phases.

Controlling dynamic recrystallization via modified LPSO phase morphology and distribution in Mg-Gd-Y-Zn-Zr alloy

Featured initial microstructures of Mg-11Gd-4Y-2Zn-0.5Zr alloy(wt%) were obtained by adjusting temperatures of solid solution and cooling methods, including island intergranular 18R and 14H LPSO phases with low-density stacking faults, differentially spaced lamellar intragranular 14H-LPSO phases, and network intergranular 18R-LPSO phases with high-density intragranular stacking faults. Effects of these featured LPSO phases and stacking faults on dynamic recrystallization(DRX) behavior were investigated via hot compression. Promoted DRX behavior via particle stimulated nucleation(PSN) is introduced by coexisting intergranular island 18R and 14H LPSO phases and intragranular wide spacing lamellar 14H-LPSO phases, contributing the highest DRX fraction of 42.6%. Conversely, it is found that DRX behavior with network intergranular 18R-LPSO phases and dense intragranular stacking fault is considerably inhibited with the lowest fraction of 22.8%. That is, the restricted DRX due to dislocations pinning by stacking faults overwhelms the enhanced DRX behavior via PSN of island intergranular 18R and 14H LPSO phases. Specially, compared with dense intragranular lamellar 14H-LPSO phases, high-density stacking faults exert a larger inhibition effect on DRX behavior.

长周期有序堆垛相(LPSO)的研究现状及在镁合金中的作用

镁合金由于具有较高的比强度、比刚度以及良好的成形性和切屑加工性等优点,在航空航天、交通以及电子产品等领域获得了广泛的应用。但是由于镁合金的绝对强度较低,使其在结构件的应用上受到了一定的限制。近年来,采用稀土元素来提高镁合金的强度已成为镁合金研究领域的热点,尤其是Mg-Zn-Y镁合金。由于m(Y)/m(Zn)比的变化,Mg-Zn-Y中的强化相也逐渐产生变化,当m(Y)/m(Zn)>1时,在Mg-Zn-Y合金中出现与镁合金基体完全共格、但富含Y、Zn元素的结构及化学成分均有序的长周期堆垛有序相(LPSO)。相比于其他第二相,LPSO相具有高硬度、良好的热稳定性、良好的阻尼性能、高抗蠕变性能、高弹性模量等特点,因此,这种新型结构强化相在镁合金中对其力学性能的影响引起了研究人员的广泛关注,成为目前镁合金强韧化的研究热点。近几年的研究多是通过快速凝固粉末冶金、铜模铸造、溶体甩带等不同的铸造方法制备出含LPSO相的镁合金,并通过改变溶质原子种类、含量及比例的方法来探究LPSO相对镁合金性能的影响,之后通过热处理、挤压和轧制等加工工艺对LPSO相的数量、尺寸和分布进行调控,进而提高镁合金的性能。而有关LPSO相的微观结构,如LPSO相结构中各原子的排列方式和具体位置等,通过第一性原理计算模拟、选区电子衍射(SADP)、高分辨率透射(HRTEM)及高角环形暗场像扫描电子显微镜(HAADF-STEM)等方法进行研究,已经建立了一个比较完善的LPSO相结构模型。同时,近几年对镁合金凝固和变形过程LPSO相结构中原子的运动研究也有了突破性的进展。在21世纪初,有研究人员通过快速凝固和热挤压的方法制备出的Mg97Zn1Y2(原子分数)合金的屈服强度和延伸率分别达到了610 MPa和5%,这些优异的力学性能归因于纳米级的LPSO相。本文综述了镁合金中LPSO相的形成机制、类型及其含LPSO相的合金体系,并对LPSO相的结构堆垛有序和化学成分有序进行了详尽的叙述,同时分析了LPSO相提高镁合金强度、塑性、抗蠕变性及高阻尼性能的机理;阐述了含LPSO相镁合金的制备工艺对其性能产生的影响;最后对含LPSO相镁合金的发展方向进行了展望。

Mg_(97)ZnY_2合金中LPSO结构的研究现状

综述了国内外几种制备Mg_(97)ZnY_2合金的工艺特点和研究现状,分析了该合金中几种不同长周期结构(Long period stacking ordered structure,简称LPSO)的形成机制及堆跺方式,提出了Mg_(97)ZnY_2合金当前研究的主要问题,并展望了Mg_(97)ZnY_2合金应用于现实生产的前景。

轧制工艺对Mg-Gd-Y-Zn-Mn合金中LPSO相及其组织性能的影响

研究"轧制+固溶+轧制"工艺和"固溶+轧制"工艺对Mg-Gd-Y-Zn-Mn合金中LPSO相及其组织性能的影响。结果表明:经"轧制+固溶+轧制"工艺处理后,合金中块状LPSO相较小,且分布弥散,合金的组织由细小的再结晶晶粒组成,最终合金获得较好的综合力学性能,抗拉强度(UTS)达到347 MPa,伸长率(EL)为11.6%;经"固溶+轧制"工艺处理后,合金中块状LPSO相较粗大,分布不均匀,由于固溶退火后析出的层状LPSO相阻碍合金的再结晶,轧制后合金中仍存在变形组织,最终合金具有相对较高的抗拉强度(UTS为358 MPa),但是伸长率较低(EL为6.6%);对比而言,"轧制+固溶+轧制"工艺易进行更大压下量轧制,进而获得更高综合力学性能。

热处理对含LPSO结构Mg-Y-Cu-Zr镁合金组织与腐蚀行为的影响

为研究长周期堆垛有序(LPSO)结构对镁合金腐蚀行为的影响,通过重力铸造制备了Mg-6.6Y-2.6Cu-1.2Zr(质量分数%)合金,并分别在420、440和460℃下固溶处理。借助SEM和XRD对合金显微组织和物相进行分析;通过腐蚀浸泡实验研究合金的耐蚀性能。结果表明,铸态Mg-6.6Y-2.6Cu-1.2Zr含有LPSO结构,随着固溶温度的升高,LPSO结构减少,晶粒尺寸增大,当固溶温度为460℃时,LPSO结构消失。不含LPSO结构的Mg-Y-Cu-Zr合金耐蚀性能优于含LPSO结构的该合金,而随着固溶温度的升高,含有LPSO结构的Mg-Y-Cu-Zr合金的耐蚀性能降低。此外,合金表现为严重的局部腐蚀行为。

18R单相Mg-Y-Zn合金经773K退火过程中14H LPSO相的析出行为（英文）

为了揭示14H相的形成机理,制备并研究了18R LPSO单相Mg-Y-Zn(简称S18)合金经773 K退火100 h的显微组织演变。结果表明:铸态S18合金主要由18R相组成(其体积分数高于93%),并含有少量的W相和α-Mg相。退火时,S18合金中的18R相保持稳定,未转变成14H LPSO结构。然而,在α-Mg相内部形成了14H层片相,其尺寸和体积分数随着退火时间的延长不断增大。TEM分析表明,14H相在α-Mg内基面堆垛层错区域独立形核。14H层片的增厚生长是界面控制过程,与基面台阶的形成密切联系。而14H层片的伸长生长属于扩散控制,与溶质元素的扩散有关。该18R单相合金中14H相的形成机理可通过反应式α-Mg'→α-Mg+14H表示。

Mg-RE合金LPSO结构的析出与控制研究进展

在Mg-RE合金中添加微量合金元素,并通过一定的工艺控制可以获得层片状的长周期堆垛(LPSO)结构,使合金的综合力学性能得到大幅度提高。LPSO结构增强镁合金已成为高强韧镁合金研究的热点。结合不同Mg-RE合金综述不同LPSO结构的类型、特点、形成条件、形成机制和控制方法以及对力学性能的影响,提出Mg-RE系合金中LPSO结构研究需要解决的主要问题和LPSO结构增强镁合金的发展方向。