Cu,Ce对Al-7Si-0.35Mg合金显微组织和力学性能的影响

采用控制变量法,研究了Cu,Ce元素添加对Al-7Si-0.35Mg合金铸态及505℃10h固溶淬火+160℃6h时效热处理后显微组织和力学性能的影响.Cu,Ce元素对热处理态合金的强度、塑性影响显著.热处理态下,Ce含量一定时,添加3.4%~4.0%的Cu元素能使Al-7Si-0.35Mg合金的断裂强度提高50%以上.添加3.6%~3.8%的Cu元素时,合金的抗拉强度超过了390MPa;Ce可以有效改善共晶硅的形态,提高合金的伸长率.当Cu含量一定时,添加0.15%的Ce,Al-7Si-0.35Mg~3.6Cu合金的伸长率从4.2%提高到7.4%.添加过量的Cu,Ce元素,合金中会生成针状的Al9Ce2Cu5Si3四元相.实验结果表明,Al-7Si-0.35Mg合金中同时添加3.6%Cu和0.15%Ce时,材料有良好的综合拉伸性能.     

稀土对Zn-15Al合金组织和耐蚀性的影响

制备了一种稀土 Zn 1 5Al合金 ,并用人工海水浸泡合金进行了腐蚀实验 ,借助金相与扫描电镜观察其腐蚀形貌及组织变化情况 .结果表明 :适量稀土的加入可细化Zn 1 5Al合金的铸态组织 ,而对合金的耐蚀性能无显著改善 ;当微量Cu、Mg及稀土复合添加时可显著改善合金的耐蚀性能 .通过实验确定了Ce的最佳含量为 0 .1 % (质量分数 ) .     

晶粒细化对Al-3.2Si-0.8Mg合金组织性能的影响

采用Al-5Ti-1B合金细化剂对Al-3.2Si-0.8Mg合金进行晶粒细化,采用金相显微镜、激光导热仪和拉伸试验机等研究晶粒细化对Al-3.2Si-0.8Mg合金微观组织、铸造流动性、力学性能与导热系数的影响.结果表明：随着Al-5Ti-1B合金细化剂添加量的增加,Al-3.2Si-0.8Mg合金的α-Al晶粒逐渐细化,铸造流动性、抗拉强度和伸长率逐渐升高,但导热系数略有下降.当Al-5Ti-1B合金细化剂的质量分数增加到0.5%时,Al-3.2Si-0.8Mg合金的晶粒被细化至平均直径约为90.9 μm,铸造流动性试样长度为867 mm,抗拉强度为234 MPa,伸长率为10.1%,导热系数为182.7 W·m^-1·K^-1.     

Al替代部分Ni对储氢合金La0.63Gd0.2Mg0.17Ni3.0Co0.3微观组织和电化学性能的影响

采用感应熔炼及退火处理制备的稀土-镁-镍系AB3.3型La0.63 Gd0.2 Mg0.17 Ni3.0-x Co0.3 A1x(x=0、0.1、0.2、0.3、0.4)储氢合金,系统研究了Al元素部分替代Ni后对合金的相结构和相组成及电化学性能的影响规律.X射线衍射(XRD)和显微电子探针(EPMA)方法分析结果表明...     

K465合金的显微组织和性能研究

研究了铸态、热处理态及含0.02%(质量分数)Mg的K465镍基铸造高温合金的显微组织、力学性能.研究结果表明:铸态K465合金组织主要由γ基体、弥散分布的γ′相、(γ+γ′)共晶和碳化物组成,室温平均抗拉强度960MPa,伸长率6.0%,975℃/230MPa条件下平均持久寿命28.1h;经1210℃/4h+空冷的固溶热处理后,晶界MC碳化物部分转变为M6C碳化物,γ′相颗粒尺寸减小到0.1～0.2μm,合金室温平均抗拉强度1055MPa,伸长率4.0%,975℃/230MPa条件下平均持久寿命为50.3h;加入0.02%(质量分数)Mg后,合金中MC碳化物球化,室温平均抗拉强度990MPa...     

Al-2Ti变质处理对Zn-6Al-3Mg合金组织与力学性能的影响

采用扫描电镜、万能电子试验机和HVS-5Z/LCD维氏硬度计观察与测试变质处理Zn-6Al-3Mg合金的凝固组织与力学性能,研究Al-2Ti变质剂加入量和变质温度对合金组织和力学性能的影响。研究结果表明:当变质温度为500℃,Al-2Ti变质剂加入量为0.5%(质量分数)时,Zn-6Al-3Mg合金组织中初晶Al-fcc相呈细小颗粒状,其体积分数最小,初晶MgZn_2相消失,Zn/Al二元和Zn/Al/MgZn_2三元共晶体的体积分数最多;当变质剂加入量为0.5%,变质温度为500℃时,Zn-6Al-3Mg合金的抗拉强度和伸长率最高,合金的综合力学性能最好。     

铸态Mg-2Nd-0.2Zn-0.4Zr-xY镁合金组织及力学性能

采用光学显微镜(OM)、扫描电子显微镜(SEM)、X线衍射分析(XRD)及力学性能测试等手段,研究不同含量稀土元素Y(4%,6%,8%,质量分数)对Mg-2%Nd-0.2%Zn-0.4%Zr镁合金铸态显微组织及力学性能的影响。结果表明:在Mg-2%Nd-0.2%Zn-0.4%Zr镁合金中添加Y可以明显细化合金晶粒,其中加入6%Y时效果最佳;合金晶粒粒径由100μm细化至35μm。未添加稀土元素的Mg-2%Nd-0.2%Zn-0.4Zr铸态合金中主要存在Mg12Nd相;加入稀土元素Y后,Nd和Y分别以Mg41Nd5和Mg24Y5化合物形式存在,合金的力学性能得到提高。其中加入6%Y的合金综合力学性能最好,抗拉强度和屈服强度分别提高至245 MPa和150 MPa,而伸长率大幅提高至16%,较未加稀土元素Y的合金提高191%;当Y含量达到8%时,合金综合力学性能下降。     

Mg-3Al-1Zn-(0~0.5)Sr镁合金铸态组织中的第二相研究

为系统研究微量Sr对铸态AZ31镁合金组织中第二相的影响,且为含Sr的Mg-Al-Zn系合金设计提供理论基础,通过X射线衍射分析(XRD)、差热分析(DSC)、扫描电镜观察(SEM)和能谱分析(EDS)等手段,对Sr含量为0~0.5(质量分数,%,下同)AZ31镁合金铸态组织中的第二相的类型及形成原因进行了分析。结果表明：铸态AZ31合金中除了Mg17Al12相以外,还存在少量的小块状Mg21(Zn,Al)17相。添加Sr含量为0.1的AZ31合金中存在Mg17Al12、Mg21(Zn,Al)17相以及少量Al4Sr相,添加Sr含量为0.3的合金组织中能观察到Al4Sr、Mg21(Zn,Al)17相以及少量Mg17Al12相,而在添加Sr含量为0.5的合金中仅能观察到Al4Sr和Mg21(Zn,Al)17相,Mg17Al12相的形成受到抑制。此外,层片状共晶Al4Sr相的数量在质量分数为0.3~0.5的区间随着Sr含量的增加显著增多。     

球磨Mg17Al12纳米晶/非晶合金的微结构和储氢性能

采用镁粉和铝粉为原料,通过高能球磨方法制备了Mg17Al12纳米晶/非晶储氢合金,系统研究了球磨时间对合金微结构和储氢性能的影响.结果表明:球磨时间对Mg17Al12合金的微结构和储氢性能有显著影响,随着球磨时间t从10 h延长到100 h,合金发生从晶态(t≤50 h)到纳米晶态(t=70 h)再到非晶态(t=100 h)的结构转变;样品的平均颗粒尺寸随着球磨时间的增加先减小后增大;球磨时间为30、70和100 h后的Mg17Al12合金在350℃时的最大储氢量(氢的质量分数)分别为4.03%、4.27%和4.18%,而相同条件下铸态Mg17Al12合金的最大储氢量只有2.85%;球磨时间为70 h的Mg17Al12纳米晶合金在200、280和320℃的储氢量分别为1.07%、3.02%和4.07%;球磨时间为100 h的Mg17Al12非晶合金在200℃时30 min内的吸氢量(氢的质量分数)可达到2.84%,分别为相同条件下纳米晶合金和铸态合金的2.7倍和5.1倍.     

添加纳米TiO2对Mg17Al12吸氢性能的影响

采用高能球磨在Mg17Al12合金中添加纳米级金红石型TiO2,并研究了材料的吸氢动力学性能、结构及微观形貌特征.研究结果表明,纳米TiO2的添加可显著地提高材料的吸氢动力学性能和吸氢量,降低吸氢温度.Mg17Al12合金在573 K及1 150 min的最大吸氢量(质量分数)仅为1.45%,而添加TiO2后,Mg17Al12合金在393 K下可快速吸氢,60 min时的吸氢量达到1.97%,在473 K下15 min内的吸氢量可达到1.68%,饱和时的吸氢量达到了3.94%.X射线衍射分析表明,添加TiO2后,Mg17Al12合金在球磨过程中没有新相生成,但放氢后会出现Al及Al3Ti等相,其中Al3Ti很可能是该反应的催化剂.     

浇注长度对流变压铸AlSi9Mg组织及性能的影响

采用自制的倾斜流变装置制备半固态合金熔体并直接进行流变压铸,研究了浇注长度对半固态AlSi9Mg组织及性能的影响。结果表明:浇注长度对抗拉强度和伸长率影响较大,对硬度和冲击韧性影响较小。浇注长度为500 mm时,抗拉强度为290 MPa,延伸率为4.1%,硬度为77.9HBS,冲击韧性为0.72 kJ/m2。流变压铸后AlSi9Mg组织晶粒尺寸明显减小,形状明显圆整。浇注长度为500 mm时,流变压铸组织中的初生固相平均尺寸为7.1μm,形状因子为0.73。     

Cu和La对Al-12.6Si合金微观组织和性能的影响

研究了La加入量为0.3%时,铜质量分数(0.3%,0.8%,1.3%,1.8%和2.5%)对共晶铝硅合金(Al-12.6Si)微观组织和力学性能的影响.结果表明:当La的加入量为0.3%时,共晶硅由片状和针状变为点状和短棒状,达到了完全变质的状态.随着铜加入量的增加,合金中的Al2Cu相的数量增多、尺寸增加,合金的抗拉强度和硬度逐渐增大,延伸率有所下降;当Cu加入量为2.5%时,Al-12.6Si-2.5Cu-0.3La合金的抗拉强度为241.4MPa,延伸率为4.82%,硬度为83.9HV,与Al-12.6Si合金相比这些力学指标分别提高了58.1%,41.8%和30.9%,合金的力学性能...     

La0.7Zr0.1Mg0.2Ni3.4-xCoxFe0.1合金的制备与电化学性能研究

在氩气保护下采用电磁感应熔炼制备La0.7Zr0.1Mg0.2Ni3.4-xCoxFe0.1（x=0.15,0.25,0.35,0.45）合金,研究合金的相结构,以及Co元素部分取代Ni元素对合金的气态储氢性能和电化学性能的影响。结果表明,合金主要由LaNi5、LaNi2以及La2MgNi9相组成。合金电极的最大放电容量分别为346.7mAh/g（x=0.15）、320.3mAh/g（x=0.25）、363.0mAh/g（x=0.35）和313.3mAh/g（x=0.45）,经过65个充放电循环后,合金电极的容量保持率从63.0%（x=0.15）增加到80.2%（x=0.35）,然后再下降到75.0%（x=0.45）。La0.7Zr0.1Mg0.2Ni3.15Co0.25Fe0.1合金具有较高的高倍率放电性能（HRD1200%=67.3）和较大的极限电流密度（IL=386.8 mA/g）,显示出其良好的电化学动力学性能。     

Effects of heat treatment on microstructure and mechanical properties of SLMed Sc-modified AlSi10Mg alloy

The influence of heat treatments on the microstructures and mechanical properties of the selective laser melting manufactured AlSi10Mg alloy modified with Sc was systematically investigated. The results showed that the addition of Sc element introduced primary Al₃Sc, which increased the heterogeneous nucleation during the solidification of AlSi10Mg alloy, and then the ultrafine network eutectic structure was obtained, and hence the tensile strength was improved significantly (nearly 23 ​%). During the heat treatment process, the network eutectic structure transformed from continuous to discontinuous, and the grain refinement was weakened with an increasing heating temperature, both of which affected the mechanical properties of the Sc modified AlSi10Mg alloy. The tensile strength decreased from 438 ​± ​10 ​MPa for the Sc-modified alloy to 208 ​± ​6 ​MPa, while the fracture strain significantly increased from 6 ​± ​0.2 ​% to 30.2 ​± ​1.2 ​% when the Sc-modified alloy was heat-treated at 325 ​°C for 12 ​h. It has been found that the desirable microstructure and mechanical properties of SLM Sc-modified AlSi10Mg alloy can be realized by controlling the heat treatment process parameters.     

Microstructure and properties of in-situ synthesized Cu-1 wt%TiC alloy followed by ECAP and post-annealing

A dispersion-strengthened copper alloy with 1 wt% TiC for commercial electrical-contact wires was prepared by in-situ reaction casting, grain-ultrafining by equal-channel angular pressing (ECAP) and subsequent annealing with aim to obtain excellent comprehensive performance. The results showed that fine TiC particles were in-situ synthesized in the as-cast Cu matrix and aggregated in clusters, and thus mechanical properties of the as-cast alloy deemed insufficient. Continued ECAP at 473 K significantly refined the grains of the as-cast alloy and improved the distribution of TiC particles. Due to multiple strengthening mechanisms, the ECAP-processed alloys maintained good conductivity with obviously enhanced tensile strength and hardness values. After post-ECAP annealing, the elongation and conductivity of the fine-grained copper alloy increased with the adequate tensile strength. The novel combined process endows the alloy appropriate performance to serve current high-frequency electrification railway systems.     

添加硼对La-Mg-Ni系(PuNi3-型)贮氢合金微观结构及电化学性能的影响

为了提出La-Mg-Ni(PuNi3型)系贮氢合金的电化学循环稳定性,在La2Mg(Ni0.85Co0.15)9合金中添加微量的B,用铸造及快淬工艺制备La2Mg(Ni0.85Co0.15)9Bx(x=0,0.05,0.10,0.15,0.20)贮氢合金,分析测试铸态及快淬态合金的微观结构与电化学性能,研究硼对合金微观结构及电化学性能的影响。结果表明:铸态合金具有多相结构,包括主相(La,Mg)Ni3相(PuNi3型)和LaNi5相,一定量的LaNi2相和微量的Ni2B相经快淬处理后,Ni2B相消失,且其他相的相对量随淬速的变化而变化。硼的加入提高了铸态及快淬态合金的循环稳定性,但使铸态合金的容量下降;铸态合金的电化学容量随B含量的增加单调下降,而快淬态合金的容量随B含量的增加有一极大值,B对铸态及快淬态合金电化学性能的影响机理是完全不同的。     

Hydrogen storage and low-temperature electrochemical performances of A2B7 type La-Mg-Ni-Co-Al-Mo alloys

The effect of Mo-addition on hydrogen storage and low-temperature electrochemical performances of La-Mg-Ni-Co-Al alloys is investigated. The alloys were synthetized via vacuum induction melting followed by annealing treatment at 1123 K for 8 h. The major phases in the annealed alloys are consisted of (La, Mg)2Ni7, (La, Mg)5Ni19 and LaNi5 phases. Mo-addition facilitates phase transformation of LaNi5 into (La, Mg)2Ni7 and (La, Mg)5Ni19 phases. Hydrogen absorption/desorption PCI curves indicates that the hydrogen storage capacity of the alloy increases remarkably with the addition of Mo. Furthermore, the La0.75Mg0.25Ni3.05Co0.2Al0.05Mo0.2 alloy shows excellent hydriding/dehydriding kinetics with a higher capacity, requiring only 100 s to reach its saturated hydrogen capacity of 1.58 wt% at low temperature of 303 K, and releasing 1.57 wt% hydrogen within 400 s at 338 K. Electrochemical experiments manifest that the Mo-added alloy electrode has perfect activation properties and the maximum discharge capacity. The low-temperature dischargeability shows that the La0.75Mg0.25Ni3.05Co0.2Al0.05Mo0.2 alloy exhibits the excellent low-temperature discharge performance, and the maximum discharge capacity is improved from 231.0 to 334.6 mAh/g at 253 K. The HRD property of the alloy electrode is enhanced, suggesting that Mo enhances the kinetic ability at low-temperature.     

Effects of Gd solutes on hardness and yield strength of Mg alloys

Relative contribution of individual strengthening mechanisms to the yield strength of Mg–0–15 wt%Gd alloys were investigated.Alloys with different grain size were prepared by adding Zr and hot extrusion.Hardness and tensile/compression yield strength were tested on the alloys after solid solution treatment and extrusion.HallPetch constants were calculated with hardness and tensile/compressive data.The results showed that the hardness of Mg–Gd alloys with similar Gd content and different grain size were almost the same,which indicates that grain size had little effect on hardness.The hardness linearly increased with rising Gd content(d H_v/dc≈25 kg mm~(-2)/at%Gd).The tensile and compressive yield strengths enhanced with the increase of Gd content for all alloys in different conditions.In addition,the tensile/compressive(t/c)yield asymmetry of extruded alloys decreased with increasing Gd content.Large t/c yield asymmetry ratio(1.77)was observed for pure Mg,and with increasing Gd content this value decreased to 1.With the increasing of tensile strength,the stress intensity factor,k_y,decreased from 0.27 MPa m~(1/2)for Mg–2 wt%Gd alloy to 0.19 MPa m~(1/2) for Mg–5 wt%Gd alloy,then increased to 0.29 MPa m~(1/2) for Mg–15 wt%Gd alloy.However,k_yincreased linearly form 0.16–0.31 MPa for compression test.The influence of grain size strengthening was eliminated,and the yield strength of tension and compression both linearly increased with c~n,where c is the atom concentration of Gd,and n=1/2 or 2/3.     

Effects of Zn content on the microstructure and the mechanical and corrosion properties of as-cast low-alloyed Mg–Zn–Ca alloys

The effects of Zn content on the microstructure and the mechanical and corrosion properties of as-cast low-alloyed Mg–xZn–0.2Ca alloys (x=0.6wt%, 2.0wt%, 2.5wt%, hereafter denoted as 0.6Zn, 2.0Zn, and 2.5Zn alloys, respectively) are investigated. The results show that the Zn content not only influences grain refinement but also induces different phase precipitation behaviors. The as-cast microstructure of the 0.6Zn alloy is composed of α-Mg, Mg₂Ca, and Ca₂Mg₆Zn₃ phases, whereas 2.0Zn and 2.5Zn alloys only contain α-Mg and Ca₂Mg₆Zn₃ phases, as revealed by X-ray diffraction (XRD) and transmission electron microscopy (TEM) analyses. Moreover, with increasing Zn content, both the ultimate tensile strength (UTS) and the elongation to fracture first increase and then decrease. Among the three investigated alloys, the largest UTS (178 MPa) and the highest elongation to fracture (6.5%) are obtained for the 2.0Zn alloy. In addition, the corrosion rate increases with increasing Zn content. This paper provides an updated investigation of the alloy composition–microstructure–property relationships of different Zn-containing Mg–Zn–Ca alloys.