Design optimization of cast Cu-Al-Be-B alloys for high damping capacity

This paper investigated high-damping Cu-Al-Be-B cast alloys using metallographic analysis, X-ray diffraction (XRD) and electrical resistance measurements for transformation temperatures. The results showed that beryllium can stabilize β phase, resulting in a thermo-elastic martensite microstructure leading to high-damping capacity in cast Cu-Al-Be-B alloys. Trace additions of boron to Cu-Al-Be alloys can significantly refine the grains, providing high strength and ductility to the alloys. A factorial design of experiment method was used to optimize the composition and properties of cast Cu-Al-Be-B alloys. The optimal microstructure for thermo-elastic martensite can be obtained by adjusting the amounts of aluminum and beryllium to eutectoid or pseudo-eutectoid compositions. An optimized cast Cu-Al-Be-B alloy was developed to provide excellent mechanical properties, tensile strength σ_b=767MPa, elongation δ=7.62%, and damping capacity S. D. C=18.70%.

Preparation of FeCoNi medium entropy alloy from Fe^(3+)-Co^(2+)-Ni^(2+)solution system

In recent years,medium entropy alloys have become a research hotspot due to their excellent physical and chemical performances.By controlling reasonable elemental composition and processing parameters,the medium entropy alloys can exhibit similar properties to high entropy alloys and have lower costs.In this paper,a FeCoNi medium entropy alloy precursor was prepared via sol-gel and coprecipitation methods,respectively,and FeCoNi medium entropy alloys were prepared by carbothermal and hydrogen reduction.The phases and magnetic properties of FeCoNi medium entropy alloy were investigated.Results showed that FeCoNi medium entropy alloy was produced by carbothermal and hydrogen reduction at 1500℃.Some carbon was detected in the FeCoNi medium entropy alloy prepared by carbothermal reduction.The alloy prepared by hydrogen reduction was uniform and showed a relatively high purity.Moreover,the hydrogen reduction product exhibited better saturation magnetization and lower coercivity.

Influence of introducing Zr,Ti,Nb and Ce elements on externally solidified crystals and mechanical properties of high-pressure die-casting Al–Si alloy

High pressure die casting(HPDC)AlSi10Mn Mg alloy castings are widely used in the automobile industry.Mg can optimize the mechanical properties of castings through heat treatment,while the release of thermal stress arouses the deformation of large integrated die-castings.Herein,the development of non-heat treatment Al alloys is becoming the hot topic.In addition,HPDC contains externally solidified crystals(ESCs),which are detrimental to the mechanical properties of castings.To achieve high strength and toughness of non-heat treatment die-casting Al-Si alloy,we used AlSi9Mn alloy as matrix with the introduction of Zr,Ti,Nb,and Ce.Their influences on ESCs and mechanical properties were systematically investigated through three-dimensional reconstruction and thermodynamic simulation.Our results reveal that the addition of Ti increased ESCs'size and porosity,while the introduction of Nb refined ESCs and decreased porosity.Meanwhile,large-sized Al_3(Zr,Ti)phases formed and degraded the mechanical properties.Subsequent introduction of Ce resulted in the poisoning effect and reduced mechanical properties.

Effects of the extrusion parameters on microstructure,texture and room temperature mechanical properties of extruded Mg-2.49Nd-1.82Gd-0.2Zn-0.2Zr alloy

Microstructure,texture,and mechanical properties of the extruded Mg-2.49Nd-1.82Gd-0.2Zn-0.2Zr alloy were investigated at different extrusion temperatures(260 and 320℃),extrusion ratios(10:1,15:1,and 30:1),and extrusion speeds(3 and 6 mm/s).The experimental results exhibited that the grain sizes after extrusion were much finer than that of the homogenized alloy,and the second phase showed streamline distribution along the extrusion direction(ED).With extrusion temperature increased from 260 to 320℃,the microstructure,texture,and mechanical properties of alloys changed slightly.The dynamic recrystallization(DRX)degree and grain sizes enhanced as the extrusion ratio increased from 10:1 to 30:1,and the strength gradually decreased but elongation(EL)increased.With the extrusion speed increased from 3 to 6 mm/s,the grain sizes and DRX degree increased significantly,and the samples presented the typical<2111>-<1123>rare-earth(RE)textures.The alloy extruded at 260℃ with extrusion ratio of 10:1 and extrusion speed of 3 mm/s showed the tensile yield strength(TYS)of 213 MPa and EL of 30.6%.After quantitatively analyzing the contribution of strengthening mechanisms,it was found that the grain boundary strengthening and dislocation strengthening played major roles among strengthening contributions.These results provide some guidelines for enlarging the industrial application of extruded Mg-RE alloy.

Study on the hydrogen absorption properties of a YGdTbDyHo rare-earth high-entropy alloy

This study investigated the microstructure and hydrogen absorption properties of a rare-earth high-entropy alloy(HEA),YGdTbDyHo.Results indicated that the YGdTbDyHo alloy had a microstructure of equiaxed grains,with the alloy elements distributed homogeneously.Upon hydrogen absorption,the phase structure of the HEA changed from a solid solution with an hexagonal-close-packed(HCP)structure to a high-entropy hydride with an faced-centered-cubic(FCC)structure without any secondary phase precipitated.The alloy demonstrated a maximum hydrogen storage capacity of 2.33 H/M(hydrogen atom/metal atom)at 723 K,with an enthalpy change(ΔH)of-141.09 kJ·mol^(-1)and an entropy change(ΔS)of-119.14 J·mol^(-1)·K^(-1).The kinetic mechanism of hydrogen absorption was hydride nucleation and growth,with an apparent activation energy(E_(a))of 20.90 kJ·mol^(-1).Without any activation,the YGdTbDyHo alloy could absorb hydrogen quickly(180 s at 923 K)with nearly no incubation period observed.The reason for the obtained value of 2.33 H/M was that the hydrogen atoms occupied both tetrahedral and octahedral interstices.These results demonstrate the potential application of HEAs as a high-capacity hydrogen storage material with a large H/M ratio,which can be used in the deuterium storage field.

铸造Cu-Al-Be阻尼合金在海水中的腐蚀行为

通过黄海和东海水域 6～ 14个月的全浸挂片试验 ,显示了经过铸态时效的Cu Al Be阻尼合金腐蚀速率为 19 3～2 5 8μm /a ,其腐蚀速度随曝露时间增加而增加 ,具有良好的耐海水腐蚀性能和一定的抗海生物污损能力。结合Neophot 2 1型光学显微镜、JSM 35C扫描电镜、DX -4型特性X射线能谱仪等手段分析讨论了合金的腐蚀特点和机理 ,Cu Al Be合金在海水中基本为单相马氏体组织 ,宏观上表现为均匀腐蚀特征 ,且无缝隙腐蚀迹象 。

热型连铸柱状晶Cu-Al-Be合金丝力学性能试验研究

采用循环加载试验,研究了热型连铸柱状晶Cu-Al-Be合金丝的超弹性力学性能,重点考察了合金丝循环加载次数及加载速率的影响,并基于试验结果提出了二种本构模型。结果表明:Cu-Al-Be合金丝具有很好的塑性变形能力和可恢复变形能力;经过循环加载训练后的Cu-Al-Be合金丝具有稳定的滞回性能,且残余变形较小;Cu-Al-Be合金丝的力学性能具有很强的率相关性;修正Wilde模型和FS模型均具有较高的分析精度,且后者计算效率更高。

用低频内耗研究Cu-Al-Be合金的相变过程

通过测量Ｃｕ－Ａｌ－Ｂｅ合金在相变范围内的低频内耗，研究了在变温和等温条件下样品内耗与频率、温度变化率等关系．在低于逆马氏体相变温度范围内，实验观测到一内耗峰，可能和相变前亚结构的变化有关．

Cu-Al-Be形状记忆合金的应力腐蚀性能

用恒载荷法和慢应变速率法及SEM研究了Cu -Al-Be形状记忆合金在甘油、海水和氨介质中的应力腐蚀性能 .结果表明 ,Cu -Al-Be合金具有良好的抗海水应力腐蚀性能和较低的氨介质应力腐蚀倾向 .单相马氏体有较好的耐海水腐蚀能力 ,可减少腐蚀引起的裂纹源 ;外应力下马氏体的孪晶变形和变体间的界面迁移 ,则有利于松弛应力集中 ,阻碍和延缓腐蚀裂纹源的扩展 ,从而提高Cu

Cu-Al-Be超弹性合金的力学性能研究

用热型连铸法制取直径为1.2mm的Cu-Al-Be超弹性合金丝,通过弯曲疲劳试验和拉伸试验,得出了Cu-Al-Be超弹性合金丝的试验结果。该合金可恢复应变量大,其数值不低于20%,最大应变高达40%;铸态下弯曲疲劳试验结果达50283次,经热处理后,弯曲疲劳试验达168480次。这些结果表明,在工程实际中Cu-Al-Be合金极有可能成为被广泛应用的新型超弹性合金。

Cu-Al-Be形状记忆合金湿磨粒磨损性能研究

采用销-盘式二体磨损试验研究了CuAlBe形状记忆合金的湿磨粒磨损行为.结果表明,CuAlBe形状记忆合金的磨损性能不完全取决于材料硬度,具有热弹性马氏体组织的A合金的抗磨性优于高硬度B合金.在湿磨粒磨损条件下,A合金具有β 1+β双相组织,在磨粒的交变应力作用下,由于β相应力诱发马氏体相变、β 1相马氏体变体择优取向并产生形状记忆效应,使应变弹性回复,并钝化裂纹尖端,使得A合金具有优良的抗磨粒磨损性能.

Al,Be含量对Cu-Al-Be-X合金相变点的影响

本文采用电阻－温度测试仪，系统地研究了合金元素Ａｌ、Ｂｅ含量对Ｃｕ－Ａｌ－Ｂｅ－Ｘ合金相变点的影响。结果表明，该合金在一定成分范围内，随着合金元素Ａｌ、Ｂｅ含量的增加，相变点Ａｓ、Ａｆ、Ｍｓ、Ｍｆ均下降，尤其是对Ｂｅ含量更加敏感。

高阻尼性能的Cu-Al-Be形状记忆合金在舰艇螺旋桨上的应用

本文论述了高阻尼性能的Ｃｕ－Ａｌ－Ｂｅ形状记忆合金在舰艇螺旋桨上减振降噪的试验研究成果。用Ｃｕ－Ａｌ－Ｂｅ合金和原实艇螺旋桨材料ＺＱＡＬ１２－８－３－２分别制作参数相同的模型桨，在相同的５６种工况下对比试验表明：用Ｃｕ－Ａｌ－Ｂｅ形状记忆合金制作的螺旋桨能够完全抑制由共振产生的异常噪声唱音，有显著的减振降噪作用。该合金在舰艇螺旋桨上应用具有一定的可行性。

等温时效过程Cu-Al-Be形状记忆合金内耗行为研究

对ＣｕＡｌＢｅ合金在等温时效过程中的内耗特性进行了研究。结果表明，等温时效时该合 金内耗主要是由应力诱发马氏体相变和Ｍ／Ｍ、Ｐ／Ｍ界面在交变应力下的粘滞性迁移所引起的。 时效过程中，合金内耗迅速下降，至一定值后趋于稳定，且大小受测量频率影响。在马氏 体态时效时，内耗衰减曲线出现峰值，这与试样中的淬火空位及其在时效时的界面扩散有 关。

Cu-Al-Be阻尼合金的抗空泡剥蚀性能

采用超声伸缩振动空蚀设备及XRD和SEM等手段 ,研究了Cu Al Be阻尼合金与对比合金ZHMn5 5 3 1和ZQAl12 8 3 2的空泡剥蚀性能。结果表明 ,Cu Al Be合金的空泡剥蚀平均速率仅为 0 .0 4mm3 /h ,相当于ZHMn5 5 3 1的 3.6 % ,ZQAl 12 8 3 2的 5 0 % ,具有优异的抗空泡剥蚀性。外力作用下Cu Al Be合金马氏体变体间的界面迁移 ,有助于减轻材料表面的塑性变形和疲劳积累 ,提高抗空蚀性能。

Cu-Al-Be-X合金阻尼性能研究

研究了Ｃｕ－Ａｌ－Ｂｅ－Ｘ合金在铸态、空冷淬火及水冷淬火态下的阻尼性能。结果表明该合金热弹性马氏体界面数量越多，过饱和空位越少，阻尼越高；并且在马氏体界面数量一定的情况下，随着应变振幅的增大，阻尼增大。

铸造Cu-Al-Be合金的超声特性

在金相观察和X射线衍射试验的基础上 ,用超声回波法测定了铸造Cu Al Be合金的超声速度和超声衰减的动态温度曲线。结果表明 ,超声速度与合金相状态有关 ,而且对热弹性马氏体相变及其逆相变非常敏感。根据超声速度随温度的异常变化可确定相变温度 ,与电阻法相比 ,超声试验测定的相变温度精确度更高。合金的超声衰减主要由各种相界面的散射引起 ,并在马氏体和母相混合区出现超声衰减峰。同时 ,超声波因诱发马氏体相变和界面迁移而消耗能量 。

Cu-Al-Be形状记忆合金的低频相变内耗研究

在变频、变温、变振幅的条件下，对ＣｕＡＩＢｅ合金的低频相变内耗进行了研究、结果表明：ＣｕＡＩＢｅ合金的连续变温相变内耗峰峰高Ｑｍ－１与变温速率ｖ和振动频率ｆ都有关，但与v、1/f或v/f都成非线性关系；峰温Tp与f无关，随v的增大而升高;温度低于Ｍｓ时，合金内耗Ｑ－１与应变振幅Aε呈线性关系。

组织及相结构对Cu-Al-Be-B形状记忆合金阻尼与力学性能的影响

研究了Cu Al Be B形状记忆合金的成分、微观组织和相结构与阻尼和力学性能的关系 ,通过扫描电镜原位观察合金在单向拉伸应力作用下裂纹萌生和扩展的特征。结果表明 :应力诱发马氏体变体的转变使Cu Al Be B合金具有较高的阻尼性能 ;弹性各向异性和相变应变差引发晶界应力集中 ,导致合金在拉伸条件下发生晶间断裂 ;18R与 2H马氏体混合程度大时 ,会增加相变应变差引起的晶界应力集中和可能萌生的晶界裂纹源 ,大大减小合金的塑性和强度。

柱状晶Cu-Al-Be合金丝等温拉拔试验研究

对柱状晶Cu-Al-Be合金丝进行了不同温度的等温拉拔试验。研究了拉拔温度对合金丝金相组织、循环拉伸性能、弯曲疲劳性能的影响。结果表明：变形温度在450℃时，合金丝产生应变诱发马氏体；在470℃时，合金丝没有马氏体和12相析出；温度在490-510℃时，合金丝析出12相，且析出物的量随变形温度的上升而增加。合金丝的残余应变量随变形温度增加先减小后增大，变形温度为470℃时，所产生的残余应变最小。当变形温度为530、550℃时，试样出现缩颈而断裂，变形温度越高，合金丝的抗拉强度越低。合金丝的弯曲疲劳性能在变形温度470℃时达最大值。