微量Sr和Mn对Mg-8Li-3Al变形合金力学性能的影响

用光学显微镜(OM)、扫描电子显微镜(SEM)、X射线衍射仪(XRD)和电子万能试验机对比研究了微量添加Sr和Mn对Mg-8Li-3Al合金组织和力学性能的影响,结果表明:基础合金Mg-8Li-3Al主要由α-Mg,β-Li和Al12Mg17金属间化合物组成,Sr和Mn的加入使合金中形成了Al4Sr和Al2Mn3等金属间化合物。合金元素Sr和Mn对合金组织均有细化效果,Sr的细化效果优于Mn。添加Sr和Mn后合金的强度均有所提高,其中挤压态Mg-8Li-3Al-0.5Sr-0.5Mn合金的σb=242.15 MPa,σ0.2=206.96 MPa,δ=22.43%,比Mg-8Li-3Al镁合金的力学性能分别提高了14.98%,28.11%和8.31%。     

Mg-TiB2中间合金和Sr对AZ91D镁合金显微组织的细化

采用SEM、EDS和XRD等测试手段研究了粉末原位合成法制备的Mg-50%TiB2(质量分数,下同)中间合金的组织和结构,以及Mg-50%TiB2和Sr对AZ91D镁合金显微组织的细化效果。结果表明,1.4%(Mg-50%TiB2)中间合金和0.1%Sr的复合添加可使AZ91D镁合金的α-Mg晶粒尺寸由基体合金的240μm降至49μm。通过面错配度计算证实TiB2可成为初生-αMg的良好异质核心。加入碱土元素Sr引起合金成分过冷度增加,从而激活固/液界面前沿潜在的TiB2核心,提高TiB2的形核率。     

Sb变质Mg-10Al合金的组织与力学性能

研究了不同Sb含量的Mg-10Al合金的微观组织及在室温和150℃高温下的力学性能。结果表明,加入适量的Sb,Mg-10Al合金中生成了弥散分布的针状Mg3Sb2相,α-Mg初晶显著细化,抑制了网状共晶组织的形成。当Sb含量为0.5%(质量分数)时,组织细化效果最佳。随着Sb含量的增加,室温及高温下合金的抗拉强度、屈服强度和伸长率先升高后降低,均在Sb含量为0.5%(质量分数)时获得最佳综合性能。Mg-10Al-0.5Sb合金在150℃的抗拉强度为180MPa、伸长率为19%,比Mg-10Al合金分别提高了30%和90%。此外,在150℃条件下,含Sb合金仍保持了与其在室温下相当的强度,而未添加Sb的Mg-10Al合金的强度则明显下降。     

Ca和La对Mg-5Sn-2Si合金组织和蠕变性能的影响

利用Mg-20%Ca(质量分数,下同)和Mg-20%La中间合金分别对Mg-5Sn-2Si合金进行变质处理,研究Ca和La对Mg2Si相的变质效果,并进行了高温蠕变实验。结果表明:Ca和La对Mg2Si相起到了良好的变质效果,初晶Mg2Si颗粒消失,粗大树枝晶得到有效细化,且有CaMgSi(花瓣状)和La5Si4(棒状)新相生成。经过Ca和La变质后合金的蠕变速率大幅度降低,在250℃和60MPa应力下,Mg-5Sn-2Si-2Ca和Mg-5Sn-2Si-2La的稳态蠕变速率分别减少到未变质时的1/48和1/28。蠕变抗力提高的原因可能与Mg2Si相细化、新相生成后位错的滑移和晶界的滑动受到阻碍有关。     

Al，Zn对挤压Mg-1Mn合金晶粒组织和塑性变形机制的影响

目的 探索镁合金中常用合金化元素Al,Zn对挤压Mg-1Mn合金的晶粒组织和力学性能的影响,为含Mn合金的成分设计及商业化应用提供理论支撑.方法 在280℃下,对Mg-1Mn,Mg-1Mn-1Al和Mg-1Mn-2Zn合金进行热挤压,制备镁合金棒材,采用拉伸测试分析力学性能,利用电子背散射衍射技术观察晶粒组织,并通过粘塑性自洽模型研究塑性变形机制.结果 在3种合金中,Mg-1Mn-1Al的晶粒最为细小,平均晶粒尺寸为1.3μm,屈服强度、抗拉强度和断裂伸长率分别为309 MPa,313 MPa和19.5％.结论 在Mg-1Mn合金中,与Zn相比,较低含量的Al具有更好的再结晶晶粒细化效果.Al,Zn的添加能够有效抑制基面滑移,促进非基面滑移的开启.     

高Ca/Al比的Mg-Al-Ca合金的超塑性

针对3种高Ca/Al比的Mg-Al-Ca合金(Mg-3.7Al-3.8Ca,Mg-4.4Al-4.5Ca和Mg-4.9Al-5.0Ca)的超塑性行为展开研究,研究结果表明,铸态镁合金具有二次相Al2Ca分布于晶界的枝晶结构。经挤压后,合金的晶粒被细化,二次相也被细化为更小的粒子。这些合金在400℃时表现出很高的伸长率,Mg-4.9Al-5.0Ca在400℃时3.6×10-4 s-1应变速率下获得最大伸长率572%。超塑性流变的变形机制为晶格扩散(DL)控制的晶界滑移(GBS)。对于挤压态Mg-4.9Al-5.0Ca合金,大部分高温稳定相Al2Ca粒子尺寸为80nm,对晶粒长大的抑制作用强烈,在晶界滑移时协调变形,因此在3种合金中Mg-4.9Al-5.0Ca具有最好的超塑性。     

等径道角挤压制备高力学性能细晶Mg-6Al合金

为了制备高力学性能细晶Mg-6Al合金坯料,采用金相显微镜、材料拉伸实验机等手段对Mg-6Al合金铸坯进行等径道角挤压实验研究.并利用热处理工艺对挤压后材料进行处理,研究热处理工艺参数对材料力学性能的影响规律.结果表明,Mg-6Al合金的铸坯的抗拉强度为196.4MPa,延伸率为12.6%.经过等径道角挤压的Mg-6Al合金坯料的晶粒被大大细化,其晶粒尺寸由铸坯的140μm左右细化到8μm左右.其力学性能有很大提高,抗拉强度由196.4MPa提高到308.2MPa;延伸率由12.6%提高到30.6%.等径道角挤压工艺是一种非常好的制备高力学性能、细晶Mg-6Al合金的工艺方法.固溶和人工时效热处理工艺对等径道角挤压的Mg-6Al合金坯料的强度有较大影响,对延伸率影响较小.     

微量钪Sc对5A01合金性能与显微组织的影响

研究了在5A01合金基础上添加0.2%Sc和0.3%Sc后合金的显微组织、力学性能、腐蚀性能及焊接性能.结果表明,微量Sc的加入,初生Al3Sc或Al3(Sc,Zr)粒子可成为有效的非均质晶核,细化合金的铸态晶粒,次生Al3Sc或Al3(Sc,Zr)粒子能有效地钉扎位错和亚晶界,稳定亚结构并强烈抑制合金的再结晶.因此,微量Sc加入使5A01合金基体强度提高,腐蚀性能和焊接性能与5A01合金相当甚至更好.     

Sc、Zr对Al-Mg-Mn合金再结晶行为及内耗性能的影响

为了研究微量Sc、Zr在Al-Mg-Mn合金中的作用,采用铸锭冶金方法制备了Al-6.0Mg-0.5Mn-(Sc、Zr)合金,通过光学显微镜、显微硬度、透射电镜组织观察和低频扭摆法测量内耗方法研究了微量Sc、Zr对Al-6.0Mg-0.5Mn的组织、再结晶行为及内耗性能的影响.研究表明:添加质量分数为0.21%Sc和0.15%Zr可显著细化Al-6.0Mg-0.5Mn合金铸态组织;粒状Al3Sc1-xZrx相对位错、晶界有强烈钉扎作用,抑制合金再结晶;冷变形后的Al-6.0Mg-0.5Mn-0.21Sc-0.15Zr合金的内耗表现出非线性特征,频率越低或温度越高,合金内耗Q-1越大.在频率为1Hz、应变振幅为4.6×10-5下,冷变形Al-6.0Mg-0.5Mn-0.21Sc-0.15Zr合金升温Q-1-T曲线上在326℃时产生内耗峰,该峰可由Al3Sc1-xZrx沉淀粒子与位错脱钉机制解释.微量Sc、Zr可以细化Al-Mg-Mn合金组织,抑制合金的再结晶,导致合金在升温Q-1-T曲线上产生内耗峰.     

添加稀土Gd对Mg-6Al镁合金组织和耐蚀性的影响

Mg-6Al镁合金具有较好的铸造性能和力学性能,目前鲜见单一稀土元素对其腐蚀性能影响的报道。通过合金制备、微观组织分析和耐蚀性测试等方法研究了稀土Gd添加量对Mg-6Al镁合金微观组织和耐蚀性能的影响。OM、SEM、EDS、XRD分析结果表明,稀土Gd的添加改善并细化了Mg-6Al合金的铸态组织,形成杆状或块状的Al2Gd新相;动电位极化、浸泡试验等测试结果表明Gd的添加显著提高了Mg-6Al合金在3.5%NaCl溶液中的耐腐蚀性能,Mg-6Al-2%Gd镁合金的腐蚀速度最小,为0.83 mm/a,且腐蚀后组织较为致密,腐蚀产物和腐蚀坑均变小,Mg-6Al-x Gd合金的腐蚀产物主要为Mg(OH)2。     

稀土元素对轧制Mg–Zn–Zr合金板材微观组织和力学性能的影响

目的 为了使Mg–Zn–Zr合金在热加工过后具有良好的力学性能及变形各向同性,在Mg–2Zn–0.5Zr合金中添加不同含量的稀土元素,研究稀土元素对Mg–2Zn–0.5Zr合金轧制后微观组织和力学性能的影响规律,以解决变形镁合金织构强、变形各向异性强的问题。方法 通过添加不同含量（0.2%和0.8%,质量分数）的混合稀土元素,采用轧制的方法制备镁合金板材。通过SEM（扫描电子显微镜）、EDS（能谱仪）、EBSD（背散射电子衍射）和电子万能试验机等对镁合金板材的成分、微观组织、织构以及拉伸过程中的应力–应变曲线进行分析。结果混合稀土元素的添加会明显提高Mg–Zn–Zr合金板材的轧制成形性,可以起到细化晶粒、弱化轧制织构的作用,能够提高材料的伸长率并改善力学性能的各向异性。混合稀土元素会与Mg、Zn在晶界处形成第二相,但并不会影响稀土元素的织构弱化效果。与较低稀土元素（质量分数为0.2%）时相比,当混合稀土元素含量较高时（质量分数为0.8%）,合金材料的力学性能各向异性更优,这主要是由于添加较多的稀土元素,形成了{■}织构,使添加较多稀土元素的合金材料的织构强度更强。结论 随着混合稀土元素...     

Microstructure,tensile properties and thermal stability of AlMgSiScZr alloy printed by laser powder bed fusion

The new generation of Sc and Zr modified Al alloys has been attracted wide concerns in aerospace industry,owing to the excellent mechanical performances and superior thermal stability than other normal Al alloys. By microalloying with Sc and Zr, the Al3(Sc, Zr) particle forms as the grain refiner during the solidification, which is extremely beneficial for the laser powder bed fusion(LPBF) processed Al alloys. In this study, a new type Al-14.1 Mg-0.47 Si-0.31 Sc-0.17 Zr alloy was additively manufactured by LPBF, and the microstructure, tensile properties and thermal stability were studied in detail. By using a single melt-67°scanning strategy, the LPBF-processed specimen with a relative density of 99.4 % and tensile strength of 487.7 MPa was obtained at 160 W-200 mm/s. And this AlMgSiScZr alloy can still exhibit an excellent tensile strength of 393.9 MPa at a moderate temperature of 473 K. After the aging treatment, the tensile properties further increased due to the precipitate hardening of Mg2 Si and Al3(Sc, Zr), and the maximum value(580 MPa) was reached at an aging time of 10 h. The average crystal size was almost unchanged after aging treated at 325°C and 24 h, indicating this AlMgSiScZr alloy has an improved thermal stability.The AlMgSiScZr alloy is recommended to substitute some particular titanium alloys in aerospace field afterwards.     

Sb对Mg-5Al-2Sr合金组织和性能的影响

采用表面活性元素Sb微合金化的方法制备了Mg-5Al-2Sr-xSb(x=0,0.3,0.6,1.0)合金,通过金相显微镜、X射线衍射仪、扫描电镜和力学性能测试等方法研究了Sb含量对Mg-5Al-2Sr合金微观组织和力学性能的影响.结果表明,Mg-5Al-2Sr-xSb合金铸态组织主要由枝晶α-Mg、沿晶界或分布在枝晶间的层状或离异共晶的Al4Sr相、块状三元Mg9Al3Sr相(τ相)和颗粒状SbSr2相组成,随着Sb含量的增加,Sb-Sr2相的数量逐渐增多,τ相逐渐减少.Sb的质量分数为0.6%时,断续分布的Al4Sr相和细小弥散分布的Sb-Sr2相能够提高Mg-5Al-2Sr合金的室温和高温(150℃)机械性能.     

Effects of Zr,Ti and Sc additions on the microstructure and mechanical properties of Al-0.4Cu-0.14Si-0.05Mg-0.2Fe alloys

The evolution of microstructure and mechanical properties of Al-0.4Cu-0.14Si-0.05Mg-0.2Fe (wt.%) alloys, micro-alloyed with Zr, Ti and Sc, were investigated. The addition of 0.2%Zr to base alloy accelerates the precipitation of Si-rich nano-phase in α-Al matrix, which plays an important role in improving the mechanical properties of an alloy. The tensile strength increases from 102 MPa for the base alloy to 113 MPa for the Zr-modified alloy. Adding 0.2%Zr + 0.2%Ti to base alloy effectively refines α-Al grain size and accelerates the precipitation of Si and Cu elements, leading to heavy segregation at grain boundary. By further adding 0.2%Sc to Zr + Ti modified alloy, the segregation of Si and Cu elements is suppressed and more Si and Cu precipitates appeared in α-Al matrix. Accompanied with the formation of coherent Al₃Sc phase, the tensile strength increases from 108 MPa for the Zr + Ti modified alloy to 152 MPa for the Sc-modified alloy. Due to excellent thermal stability of Al₃Sc phase, the Sc-modified alloy exhibits obvious precipitation hardening behavior at 350 °C, and the tensile strength increases to 203 MPa after holding at 350 °C for 200 h.     

Bi对Mg-3Al-3Nd合金显微组织和力学性能的影响

使用扫描电子显微镜(SEM)和光学显微镜(OM)观察、X-射线衍射(XRD)分析以及力学性能测试等手段研究了Bi含量对Mg-3Al-3Nd合金的显微组织和力学性能的影响。结果表明：添加Bi元素可细化Mg-3Al-3Nd合金的组织。当Bi含量(质量分数)为1%时晶粒最小,晶粒尺寸从1854±58 μm减小到890±64 μm;Mg-3Al-3Nd合金由呈网状分布在晶界的Al₁₁Nd₃相和分布在晶内的颗粒状Al₂Nd组成;随着Bi含量的提高Al₁₁Nd₃相和Al₂Nd相的数量减少,晶内的BiNd相数量增加;Bi能明显改善Mg-3Al-3Nd合金室温和高温力学性能,Bi含量为1%时其室温和高温力学性能最佳。室温抗拉强度和延伸率分别为167±2.3 MPa和(16.1±0.3)%,高温抗拉强度及延伸率分别为136±1.7 MPa和(19.3±0.3)%。     

Effect of Y and Ce on the microstructure,mechanical properties and anisotropy of as-rolled Mg-8Li-1Al alloy

The effects of combined addition of Y and Ce on the microstructure, mechanical properties and anisotropy of as-rolled Mg-8 Li-1 Al(LA81) alloy were studied. The combined addition of Y and Ce improves the mechanical properties with a low plasticity loss by solution strengthening, dispersion strengthening,grain refinement strengthening. Mg-8 Li-1 Al-0.6 Y-0.6 Ce(LA81-0.6 Y-0.6 Ce) has better mechanical properties and shows an almost isotropy. It possesses an ultimate tensile strength of 278.7 MPa and an elongation of 15.0%. Compared to LA81 alloy, the ultimate tensile strength increases by about 17.6% with an elongation reduction of only 3.5%, and a good isotropy of ultimate tensile strength and elongation(the value of r_(avg) is near 1).     

Microstructure and mechanical properties of Mg-5Li-1Al sheets prepared by accumulative roll bonding

Ultrafine-grain and high-strength Mg-5Li-1Al sheets were prepared by accumulative roll bonding (ARB) process. Evolution of microstructure and mechanical properties of ARB-processed Mg-5Li-1Al sheets was investigated.Results show that, during ARB process, the evolution of deformation mechanism of t Mg-5Li-1Al alloy is as follows: twinning deformation, shear deformation, forming macro shear zone, and finally dynamic recrystallization (DRX). The grain refining mechanism changes from twin DRX to rotation DRX. With the increase in ARB cycles, strength of the Mg-5Li-1Al sheets is enhanced, whilst elongation varies slightly. With the increase in rolling cycles, anisotropy of mechanical properties decreases. It is conclusive that strain hardening and grain refinement dominate the strengthening mechanism of Mg-5Li-1Al alloy.     

Microstructural refinement and tensile properties enhancement of Mg-3Al alloy using charcoal additions

Significant grain refinement in Mg-3Al alloy is achieved with the addition of charcoal due to the formation of Al₄C₃ particles, which act as effective nuclei for magnesium grains. Addition of 0.5 wt% charcoal has lead to reduced grain size of Mg-3Al alloy from 500 to 80 μm and no substantial grain refinement is obtained on further addition of charcoal. The results further reveal that the prolonged holding of the melt after the addition of charcoal has not affected the grain refining efficiency of Al₄C₃. Steady increase in tensile properties observed with increasing amount of charcoal addition has been attributed to the grain refinement and the presence of fine Al₄C₃ particles. The strengthening mechanisms due to charcoal addition are discussed in terms of Hall-Petch relation and dispersion strengthening. The predicted values are in good agreement with experimental results.