镁基汽车电池合金的锻造工艺及组织性能

采用不同温度进行了Mg18Al0.2Ni镁基电池合金的多向等温锻造工艺试验,并与锻造前的合金进行了显微组织、耐腐蚀性能和充放电循环稳定性的对比分析.结果表明:多向等温锻造工艺明显细化了合金晶粒,显著提高了合金的耐腐蚀性能和充放电循环稳定性;随着锻造温度从350 ℃增至450℃,Mg18Al0.2Ni镁基电池合金的内部组...     

变形温度对大塑性变形TA15合金显微组织和力学性能的影响

在600～800℃温度区间对TA15合金进行多向等温锻造,利用金相显微镜(OM)、透射电子显微镜(TEM)以及拉伸试验研究了变形温度对微观组织与力学性能的影响.结果表明:经3道次多向等温锻造后,TA15合金发生细化和球化,随变形温度的升高,等轴α机械破碎细化效应受到抑制,而片状α细化更加明显,不连续动态再结晶(dDRX...     

IN718合金近等温锻造研究

对IN718合金进行近等温锻造实验.结果表明:近等温锻造IN718合金微观组织和拉伸性能对温度场敏感,对变形量和应变速率不敏感,有利于IN718合金近等温加工成形.当成形温度较低时(980℃),晶粒细小,间隙相以短棒状析出,分散程度高,塑性性能高,但是屈服强度低;当成形温度较高时(1060℃),晶粒粗大,仅在晶界处有间隙相以针状析出,塑性性能较低,但是屈服强度好转;在1020℃近等温锻造IN718合金,晶粒细小,短棒状问隙相在晶内析出、针状间隙相在晶界处析出,拉伸性能优越,针状间隙相对屈服强度贡献显著.     

AZ31镁合金高应变速率多向锻造组织演变及力学性能

采用空气锤对AZ31合金在350℃以Δε=0.22的道次应变量进行1~12道次多向锻造变形,并对其组织和性能进行测试。结果表明:合金高应变速率多向锻造(HSRTF)组织演变分为两个阶段,累积应变∑Δε<1.32时为晶粒细化阶段,其主要机制为孪晶再结晶;累积应变∑Δε>1.32时为晶粒长大阶段,其主要机制为热激活长大。利用大量的孪晶对再结晶的促进作用,高应变速率多向锻造工艺可快速生产细晶粒高性能AZ31变形镁合金锭坯,累积应变∑Δε=1.32时,可获得组织均匀、平均晶粒度为7.4μm的锻坯,其抗拉强度、屈服强度和伸长率分别为313 MPa、209 MPa和28.6%。     

低温多向锻造锆-4合金的力学性能和超细晶组织演化（英文）

研究低温(77K)多向锻造锆-4合金累积应变为1.48,2.96,4.44和5.91时的力学性能和组织演变。通过万能拉伸测试和维氏硬度实验测得多向锻造合金的力学性能。相对于原始合金,当锆-4合金变形的累积变形为5.91时,其极限抗拉强度从474MPa提高到717MPa,维氏硬度从HV 190提高到HV 238。然而,由于锆-4合金的低应变硬化,其延展性显著降低(18%~3.5%)。变形合金强度和硬度的提高是因为多向锻造引起的晶粒尺寸效应和高的位错密度。采用光学显微镜和透射电镜表征变形试样的显微组织演化。当累积应变为5.91时,经12次多向锻造后合金的微观组织演化主要是超细晶的形成,其平均晶粒尺寸为150~250nm。     

高应变速率多向锻造对AZ31镁合金组织及耐腐蚀性能的影响

对均匀化处理后AZ31镁合金进行高应变速率多向锻造,使用金相显微镜(OM)与电子背散射衍射仪(EBSD)等测试手段研究了不同累积应变量对AZ31镁合金显微组织的影响;采用电化学测试等方法研究不同累积应变量对合金在质量分数为3.5%的NaCl溶液中的腐蚀行为。实验结果表明:相对于锻造前,高应变速率多向锻造后,合金平均晶粒尺寸大幅度减小、耐腐蚀性能提升。当累积应变量为1.32时,合金获得了均匀细小的晶粒组织,其平均晶粒度为7.8218μm,再结晶比例分数为79.40683%,平均腐蚀速率V_i=0.072 mm·a~(-1),合金耐腐蚀性能最优;当累积应变量大于1.32时,在自激活的作用下,引起了再结晶晶粒的长大,合金的再结晶程度与组织的均匀性下降,耐腐蚀性能降低。     

Mg-8Gd-1Er-0.5Zr合金多向锻造工艺及锻后组织与力学性能研究

为改善和提高Mg-8Gd-1Er-0. 5Zr合金的组织和力学性能,采用不同锻造温度和累积应变量对Mg-8Gd-1Er-0. 5Zr合金进行了等温多向锻造实验,并测试和分析了合金的组织和力学性能。实验结果表明:在实验温度范围内,随着锻造温度的升高,Mg-8Gd-1Er-0. 5Zr合金的可锻性逐步提高;在420℃锻造时,锻造初期产生大量的孪晶以协调变形,随着锻造温度升高至480℃,孪晶数量减少,再结晶晶粒数量增加,且平均晶粒尺寸有一定的增大;在累积应变量Δε=0. 66时,与420℃锻造时相比,450℃锻造后的试样强度略有降低,但伸长率明显增加,其抗拉强度、屈服强度、伸长率分别为295 MPa、252 MPa、13. 8%,但当锻造温度提高到480℃时,强度下降;当锻造温度一定时,随着累积应变量的增加,合金内部组织经历了从原始粗晶到混晶组织、再到由再结晶晶粒组成的细小均匀组织的演变,且合金在Δε=0. 66时的力学性能最佳。最终,确定了Mg-8Gd-1Er-0. 5Zr合金的锻造温度优选为450℃。     

等温锻造对Ti-17粉末合金组织与性能的影响

采用粉末真空烧结+等温锻造复合工艺制备了Ti-17粉末合金材料,并研究了等温锻造工艺对合金微观组织与力学性能的影响。结果表明:粉末烧结后的Ti-17粉末合金微观组织为魏氏组织形态;经β相变点上、下等温锻造及热处理后,原始烧结体中残留的孔隙可以充分闭合,魏氏组织被有效地破碎;但不同的等温锻造应变速率对最终微观组织形态影响较大,低应变速率会造成组织粗化、性能降低,合适的等温锻造应变速率可以使粉末合金获得良好的力学性能。     

等温锻造GH710合金组织与性能

为解决GH710合金普通锻造时变形困难、组织性能不均匀的技术问题,开展了GH710合金等温锻造工艺研究.对等温锻造GH710合金变形性能、微观组织和力学性能进行了分析,结果表明,等温锻造工艺可有效改善GH710合金变形性能、细化晶粒组织、提高合金力学性能.GH710合金经1100 ℃变形量为50%和70%的等温锻造后,均具有良好的力学性能,特别是其持久性能得到大幅度提高,815 ℃缺口持久性能达到100 h之上,980 ℃光滑持久性能达到80 h之上.采用等温锻造工艺研制出了Φ240 mm的GH710合金涡轮盘模锻件,锻件外观完整、晶粒组织细小均匀,力学性能稳定,等温锻造工艺是制备GH710合金细晶涡轮盘的理想工艺.     

等温锻造温度对2A70铝合金组织性能的影响

在6300kN四柱油压机上对2A70铝合金试样在变形温度350～480℃、应变速率0.001s~(-1)的条件下进行等温压缩试验,然后对其进行标准同溶时效处理,并进行室温拉伸性能测试和显微组织观测.实验研究结果表明,在430～450℃变形温度范围内,等温锻件的显微组织为完全再结晶组织,晶粒细小且沿变形方向分布;在430℃纵向抗拉强度和屈服强度分别达到最大值(410MPa和292.5MPa),在450℃横向抗拉强度和屈服强度分别达到最大值(400MPa和270MPa),而伸长率均远超过技术条件要求.综合考虑显微组织、强度和塑性等因素,选取450℃为该合金的较佳等温锻造温度.     

二次挤压对挤压和ECAP变形后ZK60镁合金显微组织和力学性能的影响

测试四种状态下ZK60合金的显微组织和力学性能,四种状态分别为：挤压;挤压＋4道次ECAP;挤压＋4道次ECAP＋二次挤压;挤压＋4道次ECAP＋退火＋二次挤压。在室温下成功地进行ZK60的二次挤压,得到超细晶组织。结果表明：ECAP和二次挤压可以显著细化晶粒。挤压＋4道次ECAP＋二次挤压后的ZK60合金的屈服强度为342MPa,但是其伸长率只有0.8%。在二次挤压之前进行退火,ZK60合金的伸长率可以提高到4.5%,而屈服强度基本不变,抗拉强度达到 388 MPa。     

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.     

Influence of extrusion temperature on microstructure and mechanical properties of Mg-4Y-4Sm-0.5Zr alloy

The solution-treated Mg-4Y-4Sm-0.5Zr alloy was extruded at temperatures from 325℃ to 500℃.Dynamic recrystallization(DRX) completely occurs when the alloy is extruded at 350℃and above.The grains of the extruded alloy are obviously refined by the occurrence of DRX.The average grain size of the extruded alloy increases with increasing the extrusion temperature,leading to a slight decrease of the ultimate tensile strength(UTS) and the yield strength(YS) .On the contrary,the UTS and YS of the extruded and aged alloy increase with increasing the extrusion temperature.Values of UTS of 400 MPa,YS larger than 300 MPa and elongation(EL) of 7%are achieved after extrusion at 400℃ and ageing at 200℃ for 16 h.Both grain refinement and precipitation are efficient strengthening mechanisms for the Mg-4Y-4Sm-0.5Zr alloy.     

Influence of magnesium on grain refinement and ductility in a dilute Al–Sc alloy

Experiments were conducted to determine the influence of magnesium additions on grain refinement and tensile ductility in an Al–0.2% Sc alloy processed by equal-channel angular pressing (ECAP). The experiments show ECAP reduces the average grain size to within the range of ∼0.70 to ∼0.20 μm for alloys containing from 0 to 3% Mg but the as-pressed grain size increases to ∼0.3 μm in an alloy with 5% Mg because it is then necessary to use additional annealing treatments during the pressing process. The ultrafine grains introduced by ECAP are stable to high temperatures in the alloys containing from 0 to 3% Mg: in all alloys, the average grain size is <5 μm after annealing for 1 h at temperatures up to ∼750 K. High superplastic ductilities were achieved in the alloy containing 3% Mg but alloys containing 0.5% and 1% Mg exhibited the enhanced ductilities generally associated with conventional Al–Mg alloys. The results suggest the addition of ∼3% Mg is optimum for achieving superplastic elongations at rapid strain rates in the Al–0.2% Sc alloy.     

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。     

非连续TiB+TiC颗粒增强钛基复合材料的剧烈塑性变形行为

针对TiB+TiC陶瓷颗粒增强钛合金提出一种新的强塑性变形方法,即将等径弯曲通道变形应用到非连续增强钛基复合材料中。本文采用通道夹角Φ=120°成功地实现了(TiB+TiC)/Ti6Al4V钛基复合材料1~4道次B_c路径的ECAP变形,研究了剧烈塑性变形对微观组织演化和力学性能的影响。结果表明,剧烈塑性变形可以实现TiB纤维和TiC颗粒的细化,以及基体晶粒的细化;随着挤压次数的增加,基体中偏聚的TiB细长纤维和TiC大颗粒也随着挤压道次的增加也逐渐趋于均匀化,力学性能也得到了提高,抗拉强度能够提高至1205MPa,延伸率与挤压1道次相比也得到了明显提高。     

Using equal-channel angular pressing for the production of superplastic aluminum and magnesium alloys

Equal-channel angular pressing (ECAP) is a useful tool for achieving exceptional grain refinement in bulk metallic alloys. Typically, the grain sizes produced through ECAP are in the submicrometer range, and thus they are smaller by up to an order of magnitude than the grain sizes attained through typical thermomechanical treatments. As a consequence of these ultrafine grains, the as-pressed alloys may exhibit superplastic ductilities at faster strain rates than in conventional superplastic alloys. This work initially describes the application of ECAP to two different alloys. First, results are presented for a commercial Al-2024 alloy where this alloy was selected because it contains no minor additions of either zirconium or scandium to assist in restricting grain growth. The results show that superplasticity is achieved through the use of ECAP. Second, results are described for a Mg-0.6%Zr alloy where this alloy was selected because it is the optimum composition for achieving a high damping capacity. Again, processing by ECAP produces superplastic ductilities not attained in the cast alloy. The second part of this work demonstrates that processing by ECAP may be extended from conventional rod or bar samples to samples in the form of plates. This is a very attractive feature for industrial superplastic forming applications. This paper was presented at the International Symposium on Superplasticity and Superplastic Forming, sponsored by the Manufacturing Critical Sector at the ASM International AeroMat 2004 Conference and Exposition, June 8–9, 2004, in Seattle, WA. The symposium was organized by Daniel G. Sanders, The Boeing Company.     

Er、Zr微合金化5083铝合金的超塑性

针对5E83合金(Er、Zr微合金化5083合金),采用超塑性拉伸试验、扫描电镜(SEM)、电子背散射衍射(EBSD)和透射电镜(TEM),探究了Er、Zr微合金元素、晶粒尺寸、变形温度、应变速率对合金超塑性的影响。通过再结晶退火、空冷和水冷的搅拌摩擦加工(FSP),分别获得了晶粒尺寸为7.4、5.2、3.4μm的完全再结晶组织,作为初始状态进行超塑性拉伸。结果表明,初始晶粒尺寸越细小,超塑性伸长率越高。当晶粒尺寸>5μm时,超塑性变形过程晶粒粗化缓慢,细化初始晶粒可显著提高超塑性;而当晶粒尺寸<5μm时,超塑性变形过程晶粒粗化严重,进一步细化初始晶粒对超塑性的提高有限。不同变形温度、应变速率的超塑性拉伸结果显示在变形温度为450～540℃、应变速率为1.67×10^-4～1.67×10^-1 s^-1,超塑性伸长率随变形温度和应变速率的提高呈现先上升后下降再上升的趋势;变形温度为520℃、应变速率为1.67×10^-3 s^-1条件下,水冷FSP态合金获得最大伸长率330%...     

等通道转角挤压变形Mg-1.5Mn-0.3Ce镁合金的组织、织构与力学性能

采用等通道转角挤压(ECAP)工艺以Bc路径在623K温度下对Mg-1.5Mn-0.3Ce镁合金进行变形,观察显微组织与织构,测试了力学性能。显微组织分析表明,镁合金经ECAP变形晶粒尺寸明显得到细化,经6道次ECAP变形后晶粒尺寸由原轧制态的约26.1μm细化至约1.2μm,且细小的第二相粒子Mg12Ce弥散分布于晶内及晶界处;同时经ECAP变形后,原始轧制织构随变形道次的增加不断减小,并开始转变为ECAP织构,织构强度不断增强;力学性能结果表明,由于晶粒细化作用大于织构软化作用,前3道次ECAP变形镁合金强度随道次的增加不断提高,与Hall?Petch关系相符,在第3道次时其抗拉强度和屈服强度达到最大值,分别为272.2和263.7MPa;在4道次之后形成较强的非基面织构,镁合金强度下降,与Hall?Petch呈相悖关系。断口分析表明,轧制态与ECAP变形镁合金的断裂方式都是沿晶断裂,由于6道次变形镁合金晶粒细化,存在更多的韧窝并获得16.8%最大室温伸长率。     

Effect of Various SPD Techniques on Structure and Superplastic Deformation of Two Phase MgLiAl Alloy

MgLiAl alloy containing 9 wt% Li and 1.5% Al composed of hexagonal α and bcc β phases was cast under protecting atmosphere and hot extruded. Various methods of severe plastic deformation were applied to study their effect on structure and grain refinement. Rods were subjected to 1–3 passes of Twist Channel Angular Pressing TCAP (with helical component), cyclic compression to total strain ε?=?5 using MAXStrain Gleeble equipment, both performed at temperature interval 160–200 °C and, as third SPD method, KOBO type extrusion at RT. The TCAP pass resulted in grain refinement of α phase from 30 μm down to about 2 μm and that of β phase from 12 to 5 μm. Maxstrain cycling 10?× up to ε?=?5 led to much finer grain size of 300 nm. KOBO method performed at RT caused average grain size refinement of α and β phases down to about 1 μm. Hardness of alloy decreased slightly with increasing number of TCAP passes due to increase of small void density. It was higher after MAXStrain cycling and after KOBO extrusion. TEM studies after TCAP passes showed higher dislocation density in the β region than in the α phase. Crystallographic relationship (001) α|| (110) β indicated parallel positioning of slip planes of both phases. Electron diffraction technique confirmed increase of grain misorientation with number of TCAP passes. Stress/strain curves recorded at temperature 200 °C showed superplastic forming after 1st and 3rd TCAP passes with better superplastic properties due to higher elongation with increasing number of passes. Values of strain rate sensitivity coefficient m were calculated at 0.29 after 3rd TCAP pass for strain rate range 10^?5 to 5?×?10^?3 s^?1. Deformation by MAXStrain cycling caused much more effective grain refinement with fine microtwins in α phase. Superplastic deformation was also observed in alloy deformed by KOBO method, however the value of m?=?0.21 was obtained at lower temperature of deformation equal to 160 °C and deformation rate in the range 10^?5 to 5?×?10^?3. Tensile samples deformed superplastically showed grain growth and void formation caused by grain boundary slip. Summarizing, all methods applied resulted in sufficient grain refinement to obtain the effect of superplastic deformation for alloys of two phase α?+?β structure.