等通道转角挤压Mg-3.52Sn-3.32Al合金的组织与力学性能（英文）

采用等通道转角挤压(ECAP)Bc路径对固溶态Mg-3.52Sn-3.32Al合金分别挤压1、4和8道次。利用光学显微镜、扫描电子显微镜、透射电子显微镜和X射线衍射仪分析合金的组织和相组成,并测试了其室温拉伸性能。结果表明,经ECAP挤压后,固溶态合金组织中析出大量细小的Mg2Sn相和极少量的Mg17Al12相。随挤压道次增加,合金的综合力学性能先提高后降低。经4道次挤压后,合金的综合拉伸性能相对较佳,抗拉强度、伸长率和硬度HV9.8分别达到250 MPa、20.5%和613 MPa,较未ECAP时分别提高43.7%、105%和26.9%。经ECAP挤压的合金室温拉伸断口均呈韧性断裂。等通道转角挤压Mg-3.52Sn-3.32Al合金的力学性能受晶粒尺寸、析出相以及组织织构的共同影响。     

Zn对铸态及ECAP态Mg15Al合金组织与性能的影响

采用XRD、SEM、EDS和拉伸试验,研究添加Zn元素前后铸态和等通道转角挤压(ECAP)态Mg15Al高铝镁合金的组织和力学性能。结果表明,Zn添加到Mg15Al合金中,主要固溶于β-Mg17Al12相,不生成新相。能够促进铸态Mg15Al合金中α-Mg晶粒细化,使β-Mg17Al12相质量分数增加,以及网状化加剧;使ECAP挤压后Mg15Al-1Zn合金中α-Mg基体晶粒平均尺寸由ECAP态Mg15Al合金的11.3μm减少到8.73μm,促进了β-Mg17Al12相的碎化和均匀分布;ECAP挤压能显著提高Mg15Al-1Zn和Mg15Al合金的综合力学性能,ECAP态Mg15Al-1Zn合金的抗拉强度较铸态合金提高了86%,ECAP态Mg15Al合金抗拉强度较铸态提高了60%,而且在屈服强度和塑性变化不大的情况下,ECAP态Mg15Al-1Zn合金比ECAP态Mg15Al合金室温抗拉强度提高了61.8MPa。说明Zn元素添加,能促进ECAP挤压对Mg15Al合金的晶粒细化效果,提高合金的综合力学性能。     

挤压前固溶处理对ECAP态Mg-9Al-1Si合金组织及性能的影响

采用金相(OM)、X射线衍射(XRD)、扫描电镜(SEM)、拉伸实验等方法研究了铸态和固溶态Mg-9Al-1Si合金在等通道转角挤压(ECAP)后的组织和力学性能。结果表明:铸态的Mg-9Al-1Si合金经过4道次ECAP变形后,网状Mg_(17)Al_(12)相和汉字状Mg2Si相破碎成颗粒状,但Mg_(17)Al_(12)颗粒的尺寸(~15μm)仍然很大,且Mg_(17)Al_(12)和Mg_2Si颗粒分布不均匀,削弱了合金力学性能。固溶态的Mg-9Al-1Si合金经过4道次ECAP变形后,析出细小的Mg_(17)Al_(12)颗粒(~1μm)和破碎的Mg_2Si颗粒呈均匀分布,晶粒明显细化,力学性能显著提高,抗拉强度、屈服强度和伸长率分别达到了280 MPa、178 MPa和6.8%。     

真空压铸Mg-7Al(-2Sn)合金组织性能研究及第一性原理计算

利用光学显微镜、扫描电子显微镜、能谱分析、X射线衍射、差热分析及拉伸试验比较分析了2%Sn(质量分数)对真空压铸和固溶态Mg-7Al合金的组织与力学性能的影响。结果表明,向Mg-7Al合金中添加2%Sn元素后,能够细化晶粒,抑制Mg17Al12相的生长,在组织中形成新相Mg2Sn,其以颗粒状弥散分布于基体中;固溶处理后Mg-7Al合金中第二相数目明显减少,AT72合金基体中仍存在细小颗粒状Mg2Sn。由于合金组织细化、第二相数量的增加,Mg17Al12相形貌改善以及具有良好热力学性质的Mg2Sn相的析出的综合作用,使得AT72合金表现出比Mg-7Al合金更好的室温及高温拉伸力学性能;固溶处理后的AT72合金表现出更为优异的力学性能,主要强化机制包括:固溶强化和弥散强化。此外,利用第一性原理计算从微观理论角度探讨了Sn合金化Mg-7Al合金力学性能改善的原因。     

Mg-3.52Sn-3.32Al合金轧制板材的组织和力学性能

采用同步轧制工艺对Mg-3.52Sn-3.32Al合金挤压板材在603 K进行了小变形轧制实验,用XRD、OM、SEM和TEM分析了挤压板材和轧制板材的相组成和微观组织,并测试了室温拉伸性能。结果表明:热轧后,合金板材的相组成未发生变化,仍由α-Mg基体、颗粒Mg2Sn相和块状Mg17Al12相组成。但第二相大量析出,且发生明显的动态再结晶,晶粒尺寸为5～10μm。在细晶强化、加工硬化和第二相强化的共同作用下,轧制板材的综合拉伸力学性能显著提高,抗拉强度和屈服强度分别由挤压板材的270、193 MPa提高至332、297 MPa,提高幅度分别为23%和54%。此时,伸长率为5.0%。     

等通道转角挤压Al-10Mg-4Si合金的组织与性能研究

在250℃下以Bc路径对Al-10Mg-4Si合金进行4道次和8道次的等通道转角挤压,以求达到改善合金组织和提高合金力学性能的目的.扫描电子显微镜(SEM)和透射电子显微镜(TEM)对挤压前后的微观组织分析表明:铸态合金基体晶粒比较粗大,第二相Mg_2Si以粗大的汉字状或骨骼状分布于基体晶界处;经ECAP挤压后,基体晶粒得到细化,原粗大的汉字状Mg_2Si被碎化为短棒状或多边形状颗粒,并呈一定的弥散分布.室温拉伸测试结果表明:ECAP4道次挤压后,合金的抗拉强度和伸长率由铸态的166MPa、1.64%提高为322MPa、21.7%;ECAP8道次挤压后,合金的伸长率继续提高为24.7%.但抗拉强度下降到293MPa.     

热处理对挤压态Mg-5Sn-2Si-2Sr合金组织及性能的影响北大核心CSCD

为了确定挤压态Mg-5Sn-2Si-2Sr合金合适的热处理方案,分别采用硬度计、X射线衍射仪、力学性能试验机、光学显微镜,研究了该合金经T4(固溶处理)、T5(200℃×12 h时效)和T6(固溶+时效)热处理后显微组织及力学性能的变化。结果表明:挤压态Mg-5Sn-2Si-2Sr合金宜采用T5热处理工艺。经T5热处理后,在晶界处析出大量Mg2Si强化相,使合金的屈服强度、抗拉强度分别达210.9 MPa、257.0 MPa,高于挤压态、T4和T6热处理工艺下的合金强度。T4热处理时,固溶强化作用远小于退火软化作用,致使合金力学性能的下降。T6热处理时,析出相及晶粒尺寸的长大使得合金力学性能的提高受到了限制。     

等通道转角挤压Al-Mg2Si合金的组织与性能研究

研究Al-Mg2Si合金经250℃等通道转角挤压后的微观组织与力学性能。维氏硬度及拉伸力学性能测试结果表明:经4道次ECAP挤压后,Al-Mg2Si合金的硬度、抗拉强度和延伸率均显著提高;8道次挤压后合金的塑性进一步提高,但其硬度和抗拉强度却有所下降。扫描电子显微镜和透射电子显微镜分析表明:经ECAP挤压后,原汉字状或骨骼状Mg2Si相显著碎化,且挤压道次越多,Mg2Si相的破碎效果越明显,合金组织也不断细化。对合金经较多道次挤压后硬度及抗拉强度反而有所下降的原因进行了分析。     

热处理对Mg-12Gd-3Y-Sm-0.5Zr合金组织和性能的影响

通过OM,SEM,TEM,XRD和力学拉伸实验,研究了固溶和时效热处理对Mg-12Gd-3Y-Sm-0.5Zr(质量分数,%)合金组织和力学性能的影响。结果表明,Mg-12Gd-3Y-Sm-0.5Zr合金铸态组织由α-Mg基体和含Mg5Gd相和Mg41Sm5相的粗大枝晶组成,经过固溶和时效处理后,时效析出了Mg24Y5相,Mg5Gd相演变为Mg3Gd相,固溶时效态合金纳米尺寸的长条状相的脱溶析出可有效强化合金。合金在不同状态下的室温抗拉强度为:铸态219.4 MPa、固溶态224.0 MPa和时效态299.8 MPa。     

热处理对挤压态Mg-9Sn-1.5Y-0.4Zr镁合金显微组织与力学性能的影响

本文对热处理对挤压态Mg-9Sn-1.5Y-0.4Zr镁合金显微组织与力学性能的影响进行了实验性探究。结果显示热处理对挤压态Mg-9Sn-1.5Y-0.4Zr镁合金显微组织与力学性能具有显著影响。挤压态合金主要由非均匀分布的Mg2Sn相组成。经过495℃,10h固溶处理之后,大部分Mg2Sn相溶入到基体中。时效处理能大幅改善Mg-9Sn-1.5Y-0.4Zr合金的力学性能,最佳时效工艺为：在250℃条件下时效60h。实验最终力学性能参数为：维氏硬度89HV,极限抗拉强度262MPa,屈服强度218MPa,延伸率10.4%。基于实验结果分析,可以发现对于经时效处理的挤压态Mg-9Sn-1.5Y-0.4Zr合金,沉淀强化是主要的强化因素（~51.76%）。     

等通道转角挤压制备超细晶Mg15Al双相合金组织与性能

对高铝双相合金Mg15Al在553K以Bc路线进行了不同道次的等通道挤压(ECAP),获得了超细晶高铝镁合金。通过OM,SEM,TEM分析了ECAP前后合金的微观组织结构及断口形貌,并测试了不同挤压道次后合金的硬度和室温拉伸性能,分析了ECAP细化晶粒机理及其性能改善原因。结果表明,随挤压道次增加,累计形变增强,网状硬脆相β-Mg17Al12破碎,合金晶粒显著细化,但对单相区和两相混合区细化效果不同。在α、β两相共存区内,4道次ECAP后形成100nm～200nm的细晶粒;在α单相区,4道次ECAP后晶粒为1μm以下,且在初晶α-Mg内析出弥散细小的β相,起到细晶强化和弥散强化作用。8道次ECAP后,晶粒略有长大。ECAP使合金的硬度、抗拉强度和延伸率同时得到提高,尤其是4道次ECAP后,硬度提高了32.04%,抗拉强度σb从150MPa提高到269.3MPa,延伸率δ由0.05%提高到7.4%;8道次ECAP后,硬度、抗拉强度略有下降,延伸率略有上升。SEM断口观察显示ECAP使合金拉伸断口形貌由铸态的解理断裂特征转变为延性韧窝断裂特征。     

等通道转角挤压对L2工业纯铝力学性能的影响

利用等通道转角挤压(ECAP)技术挤压工业纯铝L2，探讨了挤压次数对其力学性能的影响。结果表明，随挤压次数的增加，L2的抗拉强度和硬度得到显著提高，抗拉强度可提高95％，硬度提高70％。挤压1次后，其伸长率由40％下降至15％，此后伸长率基本保持稳定。     

Translations: BISITS—British Industrial and Scientific International Translation Service

This paper described the mechanical properties and corrosion behaviour of new designed Mg–Gd–Nd–Zn–Zr alloy processed by equal channel angular pressing (ECAP) at 375°C. An attractive phenomenon was observed. Both strength and ductility of ultrafine grained Mg–Gd–Nd–Zn–Zr alloy were improved after multipass ECAP. The microstructure of the alloys became much finer and more homogeneous with increasing ECAP passes. The yield strength, ultimate tensile strength and elongation of the alloys under eight-pass ECAP process were over 223?MPa, 270?MPa and 36% respectively, showing desirable mechanical properties of equal channel angular pressed Mg–Gd–Nd–Zn–Zr alloy. The equal channel angular pressed alloy displayed a lower corrosion resistance immersed in Hank's solution due to the crystalline defects as well as the galvanic corrosion induced by precipitation of ultrafine β phase particles.     

Microstructure evolution and mechanical behavior of AZ31 Mg alloy processed by equal-channel angular pressing

AZ31 Mg alloy bar was subjected to 8-pass equal-channel angular pressing(ECAP) at 623 K. Microstructure evolution was observed by optical microscopy(OM) on cross section and X-ray diffraction analysis. The room temperature mechanical properties of the ECAP processed specimens were also investigated. A fine-grained structure with an average sub-grain size of 9 μm is obtained after 7 ECAP passes. XRD analysis indicates that after ECAP, in placing of planes and become the dominant directions that are favourable for grain refinement. ECAP processed AZ31 Mg alloy exhibits significant improvement in elongation but decrease in strength. The elongation of the specimen increases continuously up to 2 passes and then remains stable at further passes. This improvement can be related to the evolution of crystallographic texture and the scattered orientation of the basal plane (0001).     

Strong and ductile Al–Zn–Mg–Zr alloy obtained by equal angular pressing and subsequent aging

An ultrafine-grained Al–Zn–Mg–Zr alloy with superior mechanical performance was obtained by high passes of equal angular pressing (ECAP) and subsequent aging. After 8 ECAP passes and aging, the yield strength (YS) and ultimate tensile strength (UTS) of the solid-solutioned alloy are significantly improved from (98±10) and (226±7) MPa to (405±9) and (427±9) MPa, respectively. A large elongation is also maintained ((17.4±2.5)%). The microstructure features including grain refinement, morphology of precipitates, and dislocation density, were revealed with multiscale characterizations, including transmission electron microscopy, electron backscattered diffraction, and X-ray diffraction. After 8 passes of ECAP, the original coarse elongated grains are refined to a unique bimodal grain structure consisting of ultrafine equiaxed and lath-like grains. Additionally, the effects of ECAP and subsequent aging on the strengthening contribution of a variety of strengthening mechanisms, such as dislocation strengthening and precipitation strengthening, were discussed in detail.     

Mechanical properties at room temperature of an Al-Zn-Mg-Cu alloy processed by equal channel angular pressing

Tensile tests were conducted to evaluate the influence of equal-channel angular pressing (ECAP) on the mechanical properties at room temperature of overaged Al 7075-O alloy. ECAP processing was performed using route B_C at different temperatures and number of passes, i.e. different processing severity conditions. The maximum load (F_max) recorded during the last pass of each ECAP path considered in this study is a very good estimation of the processing severity. The mechanical properties were studied in terms of the balance between tensile strength and ductility. In the processed Al 7075-O alloy, the grain size was reduced down to ∼150 nm. Consequently, tensile testing at room temperature revealed a significant increase in the maximum tensile strength after ECAP with respect to the as start material. In the present study, as the processing severity increases with the number of ECAP passes or with the decrease in processing temperature, there is a consistent trend of increment in ultimate tensile strength with minor decrease in uniform plastic elongation respect to the first ECAP pass at room temperature. This is in contrast to the behaviour after more severe plastic deformation conditions, where an increase in strength together with a strong decrease in elongation would be expected.     

Enhancing room temperature mechanical properties of Mg–9Al–Zn alloy by multi-pass equal channel angular extrusion

Influence of equal channel angular extrusion on room temperature mechanical properties of cast Mg–9Al–Zn alloy was investigated. The results show that room temperature mechanical properties of Mg–9Al–Zn alloy, such as yield strength, ultimate tensile strength and elongation, can be improved heavily by equal channel angular extrusion. Processing routes, processing temperature and extrusion passes have important influence on room temperature mechanical properties of processed Mg–9Al–Zn alloy by equal channel angular extrusion. The optimum room temperature mechanical properties such as yield strength of 209 MPa, ultimate tensile strength of 339 MPa and elongation of 14.1%, can be obtained when Mg–9Al–Zn alloy was processed by equal channel angular extrusion for 6 passes at route B_C at 498 K. Large bulk materials of Mg–9Al–Zn alloy with average grain size of 4 μm and high mechanical properties can be prepared.     

Effects of die angle on microstructures and mechanical properties of AZ31 magnesium alloy processed by equal channel angular pressing

1　INTRODUCTIONMagnesiumalloysarethelightestmetallicstruc turalmaterialsandhencetheyprovidegreatpotentialintheweightsavingofautomotiveandaerospacecomponents ,materialhandlingequipment ,portabletoolsandevensportinggoods[1,2 ] .Duetotheirhexago nalclose packed (HCP)crystalstructure ,magnesiumalloysperform poorformabilityandlimitedductilityatroomtemperature ,thustheirproductsaremainlyfabricatedbycasting ,inparticular ,die casting ,andtheapplicationsofwroughtmagnesiumalloysarelim ited .Nowit…     

Microstructure and Mechanical Properties of Cast Al-5Zn-2Mg Alloy Subjected to Equal-Channel Angular Pressing

In the present work, cast Al-5Zn-2Mg alloy was processed through equal-channel angular pressing (ECAP) in route B_C up to four number of passes. Microstructure and mechanical properties were investigated on processed and unprocessed materials. In cast condition, the material was composed of dendritic structure. After homogenization treatment, large-sized grains were observed. After ECAP processing, significant grain refinement was observed. After ECAP processing, high-density dislocations and high degree of misorientation between the grains were observed. In cast material, rod-shaped precipitates were observed, while, after ECAP processing, spherical-shaped precipitates were observed. ECAP processing leads to a noticeable improvement in the mechanical properties of the material. After four passes, 122% improvement in the microhardness and 135% improvement in the ultimate tensile strength of the material were observed. After three passes, a slight decrease in the mechanical properties was observed. This is attributed to the dissolution of the metastable η′ phase, annihilation of dislocations, dynamic recrystallization and texturing during ECAP processing. Brittle fracture mode was observed in tensile testing cast and homogenized samples. After ECAP processing, fracture mode was changed into shear fracture mode.