ZK60镁合金ECAP变形组织及力学性能

在300℃温度下对ZK60镁合金进行了不同道次的等通道挤压(ECAP).研究了ECAP挤压对合金显微组织、室温力学性能和高温抗蠕变性能的影响.结果表明,合金铸态组织主要由α-Mg基体、Mg7Zn3相和MgZn相组成.等通道挤压可显著破碎层片状MgZn相并使其趋于弥散分布,同时基体组织也得到细化.挤压2道次后,合金的室温抗拉强度由170MPa增加到250MPa,伸长率由7％增加到17.7％.挤压4道次后,合金的伸长率进一步增加到20％,而抗拉强度却下降至242 MPa;合金的高温蠕变寿命由铸态1.4h延长到44.8h,稳态蠕变速率减小了约一个数量级.     

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.     

往复挤压Mg-4Al-2Si合金的显微组织与高温力学性能

研究了往复挤压Mg-4Al-2Si合金的显微组织与高温力学性能。结果表明,往复挤压可显著细化Mg-4Al-2Si合金的组织,随着挤压道次的增加,基体晶粒与Mg2Si相颗粒不断细化,其中,基体晶粒由于动态再结晶而细化。挤压8道次时,基体晶粒和Mg2Si颗粒的平均尺寸分别由铸态的45μm和20μm减小至1.5μm和1.3μm;但是,当挤压道次为11时,基体晶粒与Mg2Si相颗粒均出现粗化现象。往复挤压可使合金的高温力学性能大幅度提高,挤压8道次时,高温屈服强度最高,为197 MPa;挤压11道次时,高温抗拉强度最高,为256 MPa,与铸态高温强度相比,分别提高了163.9%和239.7%。合金的高温强化机制为Mg2Si颗粒的弥散强化作用,高温拉伸断裂形式为微孔聚合型韧性断裂。     

等通道转角挤压Mg-6Zn-2Si合金组织及性能研究

采用等通道转角挤压变形工艺,在573 K下以Bc路径对Mg-6Zn-2Si镁合金进行4道次和8道次挤压细化合金晶粒来提高其力学性能,同时对合金室温拉伸断口进行分析,并阐述了等通道挤压改善实验合金微观组织和力学性能的机理。结果表明:经4道次挤压后晶粒由310μm细化到13μm,Mg_2Si相最大约60μm,细化为细小颗粒状约7μm,α-Mg基体与Mg Zn相均得到显著细化,屈服强度提高180%,伸长率提高140%,抗拉强度提高75%。与4道次相比,经8道次挤压后微观组织无明显变化,屈服强度有所提高,抗拉强度和伸长率变化不大。合金的室温拉伸断口由铸态合金的脆性断口过渡为韧性断口,并且韧窝加深,分布更均匀。     

等通道转角挤压对耐热镁合金AZ61-4Si组织及性能的影响

研究了镁合金AZ61-4Si等通道转角挤压前后的微观组织与力学性能。结果表明:经4道次挤压后汉字状Mg2Si相细化为细小颗粒状,基体α-Mg与离异共晶相β-Mg17Al12也得到细化;合金的屈服强度提高128%,伸长率提高340%,抗拉强度提高89%,高温蠕变断裂寿命提高8倍,蠕变速率为0.058%/h。与4道次相比,经8道次挤压后微观组织没有明显变化;屈服强度有所提高,抗拉强度和延伸率有所降低,高温蠕变断裂寿命有所下降,蠕变速率有所提高。对等通道转角挤压改善实验合金微观组织及力学性能机理进行了分析。     

改进型ECAP路径对Al-Mg_2Si原位复合材料组织与力学性能的影响

采用一种结合BC、BA路径特点的改进型路径BC-UD2、在250℃对铸造Al-10.9%Mg2Si原位复合材料进行等通道转角挤压(ECAP)来细化组织、改善Mg2Si增强相形态及分布状态,考察其对力学性能的影响。结果表明:经BC-UD2路径8道次ECAP挤压后,复合材料基体由约100μm发达的树枝晶组织细化为约1.5μm的细晶粒组织;原先粗大的汉字状共晶Mg2Si相被细化为约0.85μm的多边形状颗粒,趋于均匀分布状态,较常规BC路径中Mg2Si颗粒沿基体晶界聚集分布状态有很大改善;经BC-UD2路径挤压后复合材料的抗拉强度由铸态的166.9 MPa增大到331.8 MPa,伸长率由铸态的0.43%增加到23.6%,分别提高了99%和5 400%;同时也比BC路径挤压材料的抗拉强度(297.3 MPa)提高了12%,伸长率(15.15%)提高了56%,综合力学性能显著提高。     

ECAP对Mg-1Si合金组织和性能的影响

研究Mg-1Si铸造镁合金在挤压温度为623 K和挤压路径为BC条件下,等通道转角挤压(ECAP)不同道次变形对其组织及室温力学性能的影响。结果表明,随着挤压道次增加,α-Mg基体、Mg2Si相均得到细化且趋于均匀分布;铸态试样屈服强度为55 N/mm2,抗拉强度为93 N/mm2,伸长率为6%;1道次挤压试样的屈服强度提高67%,抗拉强度提高86%,伸长率提高95%;2道次挤压试样的抗拉强度和屈服强度与1道次相比有所降低,但伸长率进一步提高;3、4道次后试样的组织和性能相差不大;随着挤压道次增加,合金的伸长率逐渐提高,塑性提高。     

等通道转角挤压对Mg-12Al-0.7Si合金组织与性能的影响(英文)EI北大核心CSCD

研究了Mg-12Al-0.7Si镁合金在等通道转角挤压过程中微观组织与力学性能随着挤压道次的变化行为。结果表明,随着挤压道次的增加,基体晶粒不断细化。6道次细化效果最佳,从铸态约90μm细化至约8μm,连续网状分布的β-Mg17Al12相被挤碎至约4μm,汉字状Mg2Si相破碎且趋于均匀分布,8道次挤压后平均尺寸为2～3μm。室温抗拉强度和伸长率在6道次和8道次挤压后达到最高,分别为293 MPa和5.1%。高温抗拉强度和伸长率在2道次和6道次挤压后最佳,分别为204 MPa和34.4%。基面(0002)晶面取向随挤压道次增加而逐渐增强,形成基面变形织构。     

Mg-6Y-7RE-0.4Zr镁合金的显微组织和力学性能

利用光学显微镜、扫描电镜、X射线衍射、拉伸试验等方法,研究了固溶处理和挤压对Mg-6Y-7RE-0.4Zr合金显微组织和力学性能的影响,以及挤压后合金的高温力学性能。结果表明,铸态合金组织主要由α-Mg基体和Mg24Y5、Mg12RE相组成,经过固溶处理(500℃×8h)之后,Mg-Y相基本消失,Mg-RE相仍有部分存在于晶界处;室温条件下,挤压后合金塑性有了大幅度提高,抗拉强度由156MPa提高到260MPa,且出现了明显的屈服特征,屈服强度为220MPa,伸长率由0.5%提高到7.0%;高温条件下,低于250℃时挤压态合金仍保持与室温条件下相当的力学性能,300℃时强度有所降低,伸长率大幅度提高,σ=215MPa,σ=164MPa,δ=20.5%。     

往复挤压Mg-4Al-4Si镁合金的显微组织与力学性能

研究往复挤压对Mg-4Al-4Si(AS44)合金显微组织和性能的影响。结果表明:往复挤压显著地细化晶粒,改善组织的均匀性;往复挤压4道次和8道次后,Mg2Si颗粒尺寸由铸态下的约120μm分别减小至3和2μm,α-Mg基体晶粒尺寸由铸态下的约50μm分别减小至9和8μm,形成了较为细小、弥散分布的Mg2Si颗粒和细小的等轴晶组织。合金的力学性能随往复挤压道次的增加而显著提高,挤压8道次时,合金的极限抗拉强度、屈服强度和伸长率分别达到251.7 MPa、210.5 MPa和14.8%,与铸态合金相比,上述力学性能指标分别提高了131.3%、191.1%和469.2%;挤压态合金拉伸断裂形式为微孔聚合型韧性断裂。     

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Mg-3.52Sn-3.32Al合金的组织与力学性能

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力学性能。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,合金的综合拉伸力学性能相对较佳,抗拉强度、伸长率和硬度分别达到250 MPa、20.5%和61.3 HV9.8,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。     

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。     

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).     

RECIPROCATING EXTRUSION OF IN SITU Mg_2Si REINFORCED Mg-Al BASED COMPOSITE

M92Si reinforced Mg-Al based composite with high amount o/silicon was prepared by permanent mould casting, and then extruded by reciprocating extrusion （RE） after the composite was processed by homogenization heat treatment. The effect of RE processing on the morphology and size of M92Si and the mechanical properties of the com- posite were investigated, to develop new ways to refine the M928i phase and improve its shape. The result showed that RE was very useful in refining the M92Si phase. The more the RE processing passes, the better the refining effect would be. Moreover, the uniform distribution of M928i phases would be more in the composite. After the composite was processed by RE for 12 passes, most M92Si phases were equiaxed, with granular diameter below 20 μm, and distributed uniformly in the matrix of the composite. The mechanical properties of the composite could be increased prominently by RE processing, and were much higher than that in the as-cast state. As the temperature rises, the tensile strength is reduced. For the composite RE processed for 12 passes, the tensile strength, yield strength, and elongation are 325.9 MPa, 211.4 MPa, and 3.3% at room temperature, whereas, 288.2 MPa, ,207.7 MPa, and 7.8%, respectively, at 150℃. In comparison with the properties at room temperature, the tensile strength and yield strength are high and only decrease by 11.6% and 1.8% at 150℃. The M928i reinforced Mg-Al based composite possesses good heat resistance at 150℃. The excellent resistance to effect of heat is attributed to the high melting tempera- ture and good thermal stability of fine Mg2Si phases, which are distributed uniformly in the composite, and effectively hinder the grain boundary gliding and dislocation movement.     

往复挤压Mg-Al-Si合金的高温拉伸性能

利用往复挤压(RE-n,n为挤压道次)制备Mg-4Al-2Si(AS42)、Mg-4Al-4Si(AS44)和Mg-6Al-6Si(AS66)合金,并在150℃和1.33×10-3s-1的初始应变速率下测试合金的拉伸性能。结果表明:RE-8-AS42合金晶粒尺寸为2.1μm,Mg2Si颗粒尺寸为1.3μm;RE-4-AS42合金晶粒尺寸为4.8μm,组织中含有2～20μm的大块Mg2Si颗粒;RE-AS44和RE-AS66合金晶粒尺寸约为11μm,组织中存在>20μm的Mg2Si颗粒。合金拉伸强度随挤压道次增加而提高,RE-8-AS42合金性能最佳,抗拉强度、屈服强度和伸长率分别为250 MPa、197 MPa和62%,高的性能归因于细小的晶粒和阻碍晶界滑移的细小稳定Mg2Si颗粒。     

RECIPROCATING EXTRUSION OF IN SITU Mg2Si REINFORCED Mg-A1 BASED COMPOSITE

Mg2Si reinforced Mg-Al based composite with high amount of silicon was prepared by permanent mould casting, and then extruded by reciprocating extension (RE) after the composite was processed by homogenization heat treatment. The effect of RE processing on the morphology and size of Mg2Si and the mechanical properties of the composite were investigated, to develop new ways to refine the Mg2Si phase and improve its shape. The result showed that RE was very useful in refining the Mg2Si phase.The more the RE processing passes, the better the refining effect would be. Moreover,the uniform distribution of Mg2Si phases would be more in the composite. After the composite was processed by RE for 12 passes, most Mg2Si phases were equiaxed, with granular diameter below 20 μm, and distributed uniformly in the matrix of the composite. The mechanical properties of the composite could be increased prominently by RE processing, and were much higher than that in the as-cast state. As the temperature rises, the tensile strength is reduced. For the composite RE processed for 12 passes, the tensile strength, yield strength, and elongation are 325.9 MPa, 211.4 MPa,and 3.3% at room temperature, whereas, 288.2 MPa, 207.7 MPa, and 7.8%, respectively, at 150° C. In comparison with the properties at room temperature, the tensile strength and yield strength are high and only decrease by 11.6% and 1.8% at 150°C. The Mg2Si reinforced Mg-Al based composite possesses good heat resistance at 150° C. The excellent resistance to effect of heat is attributed to the high melting temperature and good thermal stability of fine Mg2Si phases, which are distributed uniformly in the composite, and effectively hinder the grain boundary gliding and dislocation movement.     

反复镦压AZ31-Mg2Si原位复合材料的组织和力学性能

采用常规铸造方法制备AZ31-4.6%Mg2Si复合材料,在400℃对铸态复合材料进行1、3和5道次的反复镦压（RU）剧烈变形。材料流动的有限元分析表明：1道次后变形集中于试样底部区域,5道次后可获得均匀的变形。多道次反复镦压过程中基体施加的剪切应力使树枝状和汉字状Mg2Si相破碎成小颗粒,随着反复镦压道次的增加,晶粒尺寸逐渐减小,Mg2Si颗粒分布逐渐均匀,同时强度和塑性显著提高,在400℃反复镦压5道次后,AZ31-4.6%Mg2Si复合材料抗拉强度和伸长率分别为248 MPa和9.8%,而原始铸态复合材料的抗拉强度和伸长率分别只有128 MPa和5.4%。