Tuning microstructure,transformation behavior,mechanical/functional properties of Ti-V-Al shape memory alloy by doping quaternary rare earth Y

The microstructure features, martensitic transformation behavior and mechanical/functional properties of Ti–V–Al alloy were tailored by changing rare element Y content in the present investigation. The results showed that Y doping resulted in the grain refinement and formation of Y-rich phase mainly distributing along grain boundary in Ti–V–Al alloys. The martensitic transformation temperatures of Ti–V–Al alloys slightly increased due to the variation of matrix composition induced by the presence of Y-rich phase. The mechanical and functional properties of Ti–V–Al alloys doped moderate Y addition were significantly improved, which can be ascribed to grain refinement, solution strengthening and precipitation strengthening. The 1.0 at.%Y-doped Ti–V–Al alloy exhibited the highest ultimate tensile stress of 912 MPa and largest elongation of 17.68%. In addition, it was found that the maximum recoverable strain of 5.42% can be obtained in Ti–V–Al alloy with adding 1.0 at.%Y,under the pre-strain of 6% condition, which is enhanced by approximate 0.6% than that of Ti–V–Al alloy without Y addition.     

Micro-alloying of yttrium in Zr-based bulk metallic glasses

The effect of yttrium addition on the glass-forming ability(GFA) and mechanical properties of the Zr-based (Zr_(0.525)Al_(0.1)Ti_(0.05)Cu_(0.179)Ni_(0.146))_(100-x)Y_x and(Zr_(0.55)Al_(0.15)Ni_(0.1)Cu_(0.2))_(100-x)Y_x(x=0,0.2,0.4 0.6,1,2) alloys was studied.Micro-alloying of 0.6%yttrium enhances the room temperature ductility as well as the GFA of the Zr-based alloys.The mechanism of enhancing the GFA and room temperature ductility was analyzed.It is indicated that proper yttrium addition stabilizes the...     

稀土元素Ce对Ti-Ni形状记忆合金力学性能的影响

采用拉伸试验研究了稀土元素Ce对Ti—Ni合金力学性能的影响,通过扫描电镜对Ti—Ni—Ce合金的断口形貌进行观察。实验结果表明,添加稀土元素Ce使Ti—Ni合金的应力-应变行为有显著影响。在马氏体状态拉伸时,当x（Ce）低于0．5％时,合金的应力-应变曲线出现明显的屈服平台;而当％（Ce）超过1％时,合金的应力-应变曲线上无明显的屈服平台,以连续屈服和强烈的加工硬化为特征。随Ce加入量增加,合金的延伸率降低、脆性增大,断裂类型由微孔聚集型的韧性断裂逐渐转变为沿晶脆性断裂。因此,Ce的加入量不能超过1％,否则将损害Ti—Ni合金的使用性能。     

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.     

Low-cost (ZrCu)50-xTax high temperature shape memory alloys showing excellent shape memory effect

ZrCu-based alloys, as one of the most potential high-temperature shape memory alloys, show quite high martensitic transformation temperature, relatively low price for the raw materials, and good casting fluidity. In this work, the martensitic transformation (MT) and shape memory effect of (ZrCu)_50-xTa_x high-temperature shape memory alloys were systematically investigated. Both X ray diffraction and SEM backscattered electron image demonstrated the coexistence of the main phase monoclinic martensite phase and the second phase Ta₂Cu. SEM results also revealed that increasing Ta content resulted in a larger volume fraction of Ta₂Cu phase. Differential scanning calorimetry results showed that the MT temperatures remarkably increased with Ta addition. The ductility of the (ZrCu)_50-xTa_x alloys was reduced to some degree with increasing Ta content. The shape memory effect was improved significantly, in which (ZrCu)₉₈Ta₂ alloy showed the 6.19% maximum recovery strain during 8% pre-strain under compression at 25 ?°C.     

Microstructural evolution and performance of hydrogen storage and electrochemistry of Co-added La0.75Mg0.25Ni3.5−xCox (x = 0, 0.2, 0.5 at%) alloys

Microstructure, hydrogen storage and electrochemical performances of Co-added La_(0.75)Mg_(0.25)Ni_(3.5_x)Co_x(x = 0,0.2, 0.5 at%) alloys are studied. XRD and rietveld refinement results suggest that the samples are mainly composed of(LaMg)Ni_3,(LaMg)_2Ni_7 and LaNi_5 phases, Co substitution for Ni changes the phase abundance,but not the phase composition. With the rising of Co content, the amount of(LaMg)_2 Ni_7 phase decreases, but the amount of LaNi_5 phase increases, while the amount of(LaMg)Ni_3 phase firstly increases and then decreases.The alloys reversibly absorb and desorb hydrogen at 298 K smoothly. When Co content is 0.2 at%, the hydrogen absorption capacity reaches the maximum value of 1.14 H/M, and the absorption capacities reach 1.09 H/M and 1.03 H/M in the first minute at 298 K and 323 K, respectively. Electrochemical performance measurement results show that La_(0.75)Mg_(0.25)Ni_(3.5-x)Co_x alloys are completely activated within 2 cycles, and the cyclic stability of La_(0.75)Mg_(0.25)Ni_(3.3)Co_(0.2) alloy approaches 63.7% after 100 charge/discharge cycles, which is higher than that(S_(100) = 60%) of La_(0.75)Mg_(0.25)Ni_(3.0)Co_(0.5) alloy. Thus, the La_(0.75)Mg_(0.25)Ni_(3.3)Co_(0.2) alloy exhibits optimum comprehensive properties of hydrogen storage and electrochemistry.     

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。     

Effect of thermo-mechanical treatment on Ti–Ta-Hf high temperature shape memory alloy

The microstructure, martensitic transformation and mechanical/functional properties of Ti–Ta-Hf alloys with various thermo-mechanical treatments were investigated. The results reveal that the hot-rolling could refine the grain size and introduce a certain number of defects, resulting in the disappearance of martensitic transformation. The as-casted and solution treated Ti–Ta-Hf alloys were composed of α'' martensite phase and smaller volume of β phase. In contrast, the grain size of solution treated Ti–Ta-Hf alloy was slightly less than that of as-casted Ti–Ta-Hf alloy. This should be responsible to the higher yield stress and superior strain recovery characteristics for solution treated Ti–Ta-Hf alloy. The yield stress for the dislocation slip and the maximum recoverable strain of solution treated Ti–Ta-Hf alloy were 723 ​MPa and 5.06%, respectively.     

AB3型储氢合金复合电极材料制备及电化学性能

以La_2Mg_(17)作为中间合金采用熔炼法成功制备了AB_3型合金La_(0．7)Mg_(0．3)Ni_(2．875)Co_(0．525)Mn_(0．1),与球磨法制得的NiB进行不同比例的复合．对合金复合前后的电化学容量、循环寿命、高倍率放电以及电化学交流阻抗(EIS)进行了测试,结果表明储氢材料经NiB复合后,合金电极循环稳定性明显提高,但是其最高放电容量有所降低；高倍率放电能力增强,抗腐蚀性能增强．     

Stability of thermal cycling and high temperature mechanical properties for Ti–V–Al–B lightweight shape memory alloy

The microstructure of the Ti–V–Al shape memory alloy with refined grain and in-situ TiB phase was modified by doping minor Boron (B), which contributes to the superior mechanical performances and strain recovery characteristics. Compared with other quaternary Ti–V–Al-X alloys, the Ti–V–Al–B alloy showed the largest ultimate tensile stress due to the solution strengthening, grain refinement and precipitation strengthening of in-situ TiB phase. Moreover, the Ti–V–Al alloy added 0.1 ?at.%B possessed the maximum yield stress of 701 ?MPa and the largest tensile fracture strain of 27.6% at the temperature of 150 ?°C. Meanwhile, the excellent strain recovery characteristics with fully recoverable strain of 4% could be obtained due to B addition. Besides, B addition suppressed the precipitation of ω phase during thermal cycling and further improved the thermal cycling stability of the Ti–V–Al alloy.     

Zr对Al-Ni-Y-(Zr,Cu)合金系非晶形成能力及热稳定性的影响

通过Zr部分取代Al80Ni10YsCu5中的Y,获得了Al80Ni10Y5-xZrxCus（x=0、1、2、3、4）铝基非晶合金．用XRD和DSC等测试手段1分析了单辊旋淬法制备的该合金非晶条带,研究了Zr对合金体系非晶形成能力和热稳定性的影响．结果表明,x=2或x=3的合金的衍射峰较为宽化;当x从0增加到2时,合金的晶化温度增加,此后,随x的进一步增加,合金的晶化温度先降低后又有所回升．Al80Ni10Y3Zr2Cu5合金既具有相对较好的非晶形成能力,又具有较高的热稳定性．     

Y对Mg-Nd-Zn-Zr铸造镁合金组织和性能的影响

采用光学显微镜、扫描电镜、透射电镜和X线衍射仪等分析研究Y对Mg-Nd-Zn-Zr铸造镁合金组织和性能的影响,并测试其室温力学性能.研究结果表明:Mg-Nd-Zn-Zr-xY(x=0,0.6％,1.2％,1.8％,质量分数)合金铸态组织主要由α-Mg和Mg12(NdaZn1-a)相组成,Y元素主要固溶在α-Mg和Mg12(NdaZn1-a)相中;合金经530℃/14h固溶处理后组织由α-Mg、残余的少量Mg12(NdaZn1-a)相以及方块状Mg24RE5相组成;固溶态合金经200℃/12h时效处理后有大量尺寸为10nm左右的β'和β”析出相生成,能有效地强化基体;随Y质量分数增加,合金室温抗拉强度和屈服强度逐渐上升,最高分别达到271 MPa和161 MPa,较基础Mg-Nd-Zn-Zr合金有较大幅度提高.     

Mg-50wt.%Ti_(1-x)C(x=0.1,0.2,0.3,0.4)合金的贮氢性能研究

采用机械合金化方法制备Mg-50wt.%Ti1-xCx(x=0.1,0.2,0.3,0.4)贮氢合金.x-射线衍射(XRD)分析结果表明,合金主要由Mg、Ti、c以及二元合金相Ti2C0.06和Mg2C3组成,随着球磨时间增加,合金的非晶化程度提高.压强-成分-温度(Pcr)测试结果显示,Mg-50wt.%Ti1-xC(x=0.1,0.2,0.3,0.4)合金的贮氢量分别为2.96、2.95、2.76、2.6wt.%;随着碳含量的增加,样品吸氢量逐渐减少,放氢温度和平台压也随之下降;适当增加球磨时间可降低吸放氢温度.     

Internal friction behaviors of Ni-Mn-In magnetic shape memory alloy with two-step structural transformation

The internal friction (IF) behaviors of dual-phase Ni52Mn32In16 alloy with two-step structural transformation were investigated by dynamic mechanical analyzer. The IF peak for the martensite transformation (MT) is an asymmetric shoulder rather than those sharp peaks for other shape memory alloys. The intermartensitic transformation (IMT) peak has the maximum IF value. As the heating rate increases, the height of the IMT peak increases and its position is shifted to higher temperatures. In comparison with the IMT peak, the MT peak is independent on the heating rate. The starting temperatures of the IMT peak are strongly dependent on frequency, while the MT peak is weakly dependent. Meanwhile, the heights of both the MT and IMT peak rapidly decrease with increasing the frequency. This work also throws new light on their structural transformation mechanisms.     

La3-xYxMgNi14(x=0～2)贮氢合金的相结构与电化学性能研究

系统研究了La3-xYxMgNi14(x=0,1.0,1.5,2.0)贮氢合金的相结构和电化学性能.结构分析表明,合金均由Gd2Co7和Ce2Ni7型结构相组成.随Y含量值x的增加,Gd2Co7型相的丰度增加,Ce2Ni7型相的丰度减少.合金各相的晶胞参数(a,c)和晶胞体积(V)均随x的增加而线性减小.电化学研究表明,随着Y含量的增加,合金电极最大放电容量减小,活化性能显著降低.合金随x的增加,HRD值减小与合金电极电催化活性及氢在合金相中的扩散速率的减小有关.     

稀土Y对挤压态Mg-5Li合金组织及性能的影响

采用表面覆盖剂及氩气保护的熔炼方法制备了Mg-5Li-x Y(x=0,1,2,3,4)合金,研究了稀土元素Y对挤压态Mg-5Li合金的显微组织及力学性能的影响.研究结果表明,Mg-5Li合金中的Y元素主要是以稀土化合物Mg24Y5的形式存在于合金中;挤压变形后,合金发生了明显的动态再结晶,出现了大量的等轴晶,弥散分布的Mg24Y5相阻碍了动态再结晶过程中的晶粒长大,晶粒明显细化.挤压态Mg-5Li-3Y合金获得了优异的力学性能,其抗拉强度和断裂伸长率分别达到了231.63 MPa和9.35%,合金断裂方式主要为韧性断裂.     

Cu,Zr对Al-Ni-Zr-Cu-Y非晶合金的形成和热稳定性的影响

采用单辊旋淬技术,在真空条件下制备了快速凝固Al85Ni10Zr3Y2四元合金条带和Al80Ni10Zr8-xCuxY2(x=1,2,3,5)五元合金条带.利用X射线衍射及差热分析对条带进行了研究.结果表明,w(Cu)和w(Zr)对该合金系的非晶形成能力及热稳定性有显著影响,并且非晶合金的形成对这两种元素的质量分数很敏感.当w(Cu)和w(Zr)其中一种达到一较大值时,可以形成非晶合金或是以非晶相为主的合金,否则将只能得到晶体相.另外,Al80Ni10Zr7Cu1Y2,Al80Ni10Zr3Cu5Y2合金系具有较强的非晶形成能力,可形成完全非晶或以非晶为主体和部分晶体的复相材料.     

考虑温度记忆效应的形状记忆合金本构模型

近年来在形状记忆合金（Shape Memory Alloy,SMA）中发现的由于不完全马氏体逆相变引起的温度记忆效应,在智能材料与结构等领域具有潜在的应用价值,建立克服现存SMA本构模型不能考虑SMA温度记忆效应这一局限性的SMA本构模型具有理论和工程实际意义．本文在前期研究的基础上,基于作者提出的形状记忆因子的概念,综合运用热力学、连续介质力学和马氏体相变学的相关理论,建立了描述SMA的形状记忆因子、应力、温度间关系的形状记忆方程和描述SMA的应变、应力、温度间关系的力学本构方程．由形状记忆方程和力学本构方程构成的SMA本构模型,克服了现存SMA本构模型不能考虑SMA温度记忆效应的局限性．数值结果表明,该SMA本构模型能有效描述经历不完全马氏体逆相变的SMA的热力学行为,可为SMA温度记忆效应的应用研究提供理论基础．     

超细片层NbTi/TiNi记忆合金复合材料的制备与功能特性

基于NbTi-TiNi共晶型相变,经成分分析,通过电弧熔炼制备几种具有NbTi和TiNi记忆合金铸态双相组织的NbTiNi合金。这种合金是一种原位自生的NbTi/TiNi记忆合金复合材料,具有复合比可控(通过调整Ni或Nb含量)、可逆马氏体相变温度可调(通过调整Ti/Ni比例)的特点。通过对其辅以常规的锻造、拔丝等大变形工艺加工,使NbTi和TiNi组元细化至微米级别,进一步得到复合组元比表面大、分布均匀、界面强度高的超细片层NbTi/TiNi记忆合金复合丝材料。通过热膨胀仪和万能拉伸试验机对其进行热膨胀和力学性能测试。结果表明,该复合材料不但具有很高的屈服强度(超过1.6 GPa),还具有负膨胀点记忆效应、应变软模效应等新功能特性。     

变形镁合金的研究热点概述

铸造工艺是镁合金件制造的主流,但经过塑性加工成形的镁合金产品具有更好的力学性能,可适应更为多变的工况需求。国际镁业协会认为,镁合金的长期发展目标应放在新变形镁合金与新成形工艺的开发与研究上。该文概述了变形镁合金目前在世界上的研究热点,分析了中国研究者的变形镁合金研究特点并建议在提高镁合金板材常温下的塑性成形性能方面多做工作,以增强中国镁合金深加工的技术能力。