Mg67Zn28Ca5合金激光表面熔凝处理及其生物腐蚀性能

镁锌钙合金因为具有较高的比强度和优异的可降解性,有望成为新一代的内固定材料,但是镁合金耐生理腐蚀能力相对较差而限制了其临床应用。通过激光熔凝处理对共晶成分的Mg67Zn28Ca5合金进行了表面改性,研究了Mg67Zn28Ca5合金激光熔凝处理前后的显微组织、相结构和元素分布;以及在人工模拟体液中合金激光熔凝处理前后的生物腐蚀性能。研究结果表明,Mg67Zn28Ca5合金经过激光熔凝处理后,在合金的表层形成了平均厚度约508.1 μm的熔凝层,该熔凝层平均晶粒大小约10 μm。与铸态和固溶态的合金相比,熔凝层在人工模拟体液中的腐蚀电位分别正移了76 mV和60 mV;熔凝层的腐蚀速率分别降低了82%和78%,为0.0468 mm/a。经激光熔凝处理后,合金表面的氧化膜也更为致密,提高了镁合金的耐腐蚀性能。MgZn2相含量减少和第二相尺寸的减小,降低了电偶腐蚀的程度,抑制了α-Mg基体相的腐蚀。     

高阻尼高强度铸态SiCp/Mg94Zn5Y1 复合材料的综合性能

采用铸造方法制备具有不同SiC_p含量（0.5%~2.0%,质量分数,下同）的SiC_p/Mg₉₄Zn₅Y₁复合材料,并研究了复合材料的力学性能和阻尼性能。通过扫描电子显微镜和X射线衍射仪测试复合材料的微观组织结构和物相组成。在基体中加入SiC_p之后,SiC_p均匀分布在基体中,增强体细化了复合材料的微观组织结构。SiC_p/Mg₉₄Zn₅Y₁复合材料包括α-Mg、I相（准晶相）和SiC_p相。分别使用动态热机械分析仪和AG-X试验机测试了SiC_p/Mg₉₄Zn₅Y₁复合材料的阻尼性能和力学性能。复合材料的力学性能优于Mg₉₄Zn₅Y₁合金,1.0%SiC_p/Mg₉₄Zn₅Y₁复合材料的抗压缩强度高达350 MPa;所有复合材料的阻尼性能都远高于基体合金的阻尼性能,其中0.5%SiC_p/Mg₉₄Zn₅Y₁复合材料具有最佳的阻尼性能。此外,根据功效系数法,SiC_p含量为1.0%的SiC_p/Mg₉₄Zn₅Y₁复合材料具有良好的综合性能。     

γ-TiAl合金表面Al2O3/Al复合涂层的抗高温熔盐腐蚀性能研究

采用磁控溅射技术于γ-TiAl合金表面制备Al₂O₃/Al复合涂层。在850 °C下、 100 wt.% Na₂SO₄熔盐中观测Al₂O₃/Al复合涂层的高温腐蚀行为。结果表明,Al₂O₃/Al复合涂层具备由Al₂O₃表层、富Al中间层以及互扩散层组成的梯度结构,因而有效地提高了基体γ-TiAl合金的抗高温腐蚀性能。在腐蚀实验后,涂层试样表面相结构为Al₂O₃,TiO₂和TiAl₃。致密的Al₂O₃/Al复合涂层有效地抑制了O_2-,S_-和Na₊对基体γ-TiAl合金的侵蚀。并且,Al₂O₃/Al复合涂层的梯度结构亦使其表现出了优异的抗开裂和抗剥落性能。     

NiTi合金激光熔凝处理及其生物腐蚀性能研究

目的 通过对NiTi合金表面进行激光熔凝处理,从而提高NiTi合金的耐腐蚀性能。方法 利用紫外激光器对NiTi合金进行表面熔凝处理,借助扫描电子显微镜(SEM)、光学显微镜(OM)、能量色散X射线光谱仪(EDX)和X射线衍射仪(XRD)等技术手段,研究了激光熔凝处理前后NiTi合金的表面显微组织、成分和相结构。测试了激光熔凝处理前后NiTi合金表面与模拟体液(SBF)的接触角、熔凝层的显微硬度等表面性能。通过全浸腐蚀试验和电化学测试,研究了熔凝层在SBF溶液中的生物腐蚀性能,并分析了腐蚀机理。结果 NiTi合金经过激光熔凝处理后,在合金的表层形成了厚度为90~150 μm的熔凝层,熔凝层主要由TiO2、β相以及少量的TiO相组成。合金表面的平均显微硬度提高了153~279HV,合金的表面接触角增大,由亲水性转为疏水性。相较于未处理的样品,熔凝处理后的样品在SBF溶液中的腐蚀电位分别正移了435 mV和413 mV,腐蚀电流密度分别下降了83%、62%左右。熔凝处理后的样品在SBF溶液浸泡168 h后,SBF溶液中的Ni²⁺浓度下降了约1/3。结论 以适当的激光加工参数对NiTi合金进行激光熔凝处理,可在NiTi合金表面形成致密的氧化膜,这层氧化膜和熔凝层可以有效地抑制NiTi合金在SBF溶液中的点腐蚀行为。     

Mg60Cu30Y10块体非晶合金的变温晶化行为

采用示差扫描量热仪(DSC)得到Mg60Cu30Y10块体非晶合金在不同加热速率下的DSC曲线。利用Losocka、Kissinger以及Doyle方法研究了Mg60Cu30Y10块体非晶合金的非等温晶化动力学。结果表明:Mg60Cu30Y10块体非晶合金具有良好的热稳定性。通过Kissinger方法计算得到的其玻璃转变激活能(Eg)、晶化激活能(Ex)以及晶化峰值激活能(Ep)分别为160.07 kJ/mol、136.11和145.19 kJ/mol。随着加热速率的提高,各特征温度值向高温端移动。局域晶化激活能随着复合材料晶化体积分数的增加先增大后减小。     

Cu44.25Ag14.75Zr36Ti5非晶合金的晶化行为

采用铜模铸造法制备了直径为3mm的柱状Cu44.25Ag14.75Zr36Ti5块体非晶合金,X射线衍射证明试样为完全非晶态。利用差示扫描热分析仪(DSC)、X射线衍射,研究了该非晶合金的晶化行为。利用Kissinger和Ozawa方程求得Cu44.25Ag14.75Zr36Ti5第一晶化峰和第二晶化峰的晶化激活能。结果表明,该大块非晶合金具有良好的热稳定性,在10K/min的加热速率下,析出相主要是Cu8Zr3和Cu10Zr7。     

TC4合金表面Ni-SiC-Y2O3复合镀层的摩擦磨损性能

为提高TC4合金表面耐磨性能,采用复合镀方法在其表面制备Ni-SiC-Y_2O_3复合镀层,研究镀层的组织结构及其在常温和高温下(600℃)下的摩擦磨损行为。结果表明,所制备的Ni-SiC-Y_2O_3复合镀层组织致密且与基体结合紧密,主要由Ni基体和弥散分布其中的SiC颗粒及微量Y_2O_3混合组成。镀层的硬度明显高于TC4基体合金,且由表向内呈梯度降低趋势。与GCr15对摩时,Ni-SiC-Y_2O_3复合镀层在常温和600℃均具有一定程度的减磨作用,并且耐磨性能明显优于TC4基体合金。镀层在常温下的磨损失重显著低于TC4基体合金,此时其磨损机制可以归结为疲劳磨损和轻微的氧化磨损;随磨损温度升高至600℃,镀层的磨损失重明显增大,此时的磨损机制为严重的氧化磨损、削层磨损和疲劳磨损。     

不同形态和热历史条件下Zr55Al10Ni5Cu30非晶合金的晶化行为

研究了不同形态Zr₅₅Al₁₀Ni₅Cu₃₀非晶合金（块体和粉末）在不同升温和冷却条件下的晶化行为.发现Zr₅₅Al₁₀-Ni₅Cu₃₀在不同热历史下的晶化行为有较大差别.对于块体非晶合金,在常规热处理条件下,合金的升温和冷却速率较低,Zr₅₅Al₁₀Ni₅Cu₃₀块体非晶合金在初始晶化温度Tx以上开始晶化,形成CuZr₂纳米晶.随着热处理温度的升高,晶粒尺寸增大,当热处理最终温度超过熔点后,合金在随炉冷却过程中形成了粗大的CuZr₂板条+板条间（CuZr₂）+（Zr,Cu,Al,Ni）共晶组织;在激光熔凝条件下,合金的升温和冷却速率较高,Zr₅₅Al₁₀Ni₅Cu₃₀块体非晶合金随单点熔凝次数的增加,晶化效应逐渐累加,热影响区中逐渐出现微米级球晶的弥散析出,并长大,随后失稳形成沿熔池边界带状分布,尺寸可达几百微米的等轴晶.对于粉末非晶合金,由于Zr₅₅Al₁₀Ni₅Cu₃₀非晶粉末的冷却强度不如块体非晶,冷却速率较块体低,造成粉末颗粒在激光熔凝过程中晶化为微米级的等轴枝晶,并随着激光能量的升高,等轴枝晶尺寸增大.     

Ti-Cu-Ni-Nb-Al-Zr-Hf非晶钎料合金真空钎焊Ti50Al50 接头的界面组织与剪切强度

在钎焊温度1140~1220 ℃、钎焊时间30 min的工艺参数下,采用Ti-9.5Cu-8Ni-8Nb-7Al-2.5Zr-1.8Hf（质量分数,%）非晶钎料成功实现了Ti₅₀Al₅₀ (at%)合金的真空钎焊连接,并研究了钎焊温度对钎焊接头的显微组织、剪切强度的影响规律。结果表明,在任何钎焊温度下获得的Ti₅₀Al₅₀钎焊接头均有3个界面反应层且每个反应层都含有α₂-Ti₃Al和Ti₂Cu(Ni) 2个物相。随着钎焊温度的增加,α₂-Ti₃Al和Ti₂Cu(Ni)在钎焊接头中的尺寸与分布发生了明显的变化,尤其是等温凝固层Ⅱ中的Ti₂Cu(Ni)相。1200 ℃下稳定存在的连续α₂-Ti₃Al层Ⅰ对母材和钎料原子的相互扩散具有阻隔壁垒作用,温度一旦超过1200 ℃,α₂-Ti₃Al相变得不稳定使得连续α₂-Ti₃Al层被打破从而失去阻隔壁垒效应。在钎缝中析出且弥散分布的α₂-Ti₃Al对焊缝中物相的形成可以起到抑制形核和细化晶粒的作用。随着钎焊温度升高,Ti₅₀Al₅₀钎焊接头平均抗剪切强度先增加后减小,在钎焊温度1180 ℃、钎焊时间30 min时钎焊接头的抗剪切强度最大,达184 MPa。剪切断口表面呈典型解理断裂特征且α₂-Ti₃Al占绝大多数。     

AB3 型 Mm0.78 Mg0.22 Ni2.48 Mn0.09 Al0.23 Co0.47储氢合金的表面氟化处理

目的提高AB3型储氢合金的电化学性能,扩大其应用范围。方法运用HF和NaF组成的溶液对AB3型合金Mm0.78Mg0.22Ni2.48Mn0.09Al0.23Co0.47(Mm由82.3%La和17.7%Nd(均为原子数分数)组成)进行表面处理,考察改性处理对合金相结构、电化学性能以及动力学性能的影响。结果氟化处理后有MgF2相生成,合金电极的最大放电容量得到提高,50次循环后的容量保持率由83.3%提高到92.8%。此外,合金的动力学性能也得到一定改善。结论氟化处理改变了合金的表面结构,提高了其电化学性能。     

Effect of nano-CeO2 on cobalt-based alloy laser coatings

Cobalt-based alloy coatings with/without nano-CeO₂ addition prepared by a 5 kW CO₂ laser on Q235 low carbon steel were introduced. The effects of nanoparticles on the macro-quality, microstructure, phase composition, and wear resistance of the coatings were investigated. The microstructure and phases composition of the coatings were analyzed using Olympus-Pme-3 type microscope, Philip Xl 30 type scanning electron microscope and XD-3A type X-ray diffractometer (XRD). The wear resistance was tested using MM-200 type sliding wear machine, and the wear mechanism was analyzed by JSM-35C type scanning electron microscope (SEM). The results showed that defect (such as crack, gas hole, etc.) -free coatings were obtained. There existed γ-Co and Cr₂₃C₆ in cobalt-based alloy coatings. Another two phases of CeCo₂ and -Co were identified with nanoparticles addition. Fine microstructure and equiaxed dendrite were obtained by adding nano-CeO₂. The relative wear resistance is improved with the increased amount of nano-CeO₂, and the coatings with the best wear resistance when laser power was 2.0 kW by adding 1.5 wt.% CeO₂. The mechanism was found from abrasive/adhesive wear to fretting wear. The wear resistance decreased with 2.0 wt.% CeO₂ addition.     

Microstructural modifications induced by hydrogen absorption in Mg5Ga2 and Mg6Pd

We have recently proposed a new method to design one-dimensional structures of MgH₂ in the nano- and micrometer ranges by hydrogen-induced disproportionation of bulk Mg₂₄Y₅. The present study confirms the same behavior in hydrogenated Mg₅Ga₂ and Mg₆Pd. Single-crystalline one-dimensional structures and microparticles of MgH₂ are formed by hydrogen absorption and subsequent partial disproportionation of Mg₅Ga₂ and Mg₆Pd. The MgH₂ whiskers and particles grow with different morphologies for different alloying partners. Growth mechanisms are proposed in relation to the morphology and the chemical surface composition of original compounds.     

Li对快速凝固Mg96.5Gd2.5Zn1合金微观组织和力学性能的影响

本文考察了快速凝固条件下不同含量Li元素添加对长周期有序结构相增强Mg-Gd-Zn合金微观组织和力学性能的影响。结果表明,随着Li元素的添加,铸态合金中Gd、Zn溶质原子在镁基体晶粒中的过饱和度降低、(Mg,Zn)₃Gd晶界析出相增加、镁基体晶粒尺寸减小。而固溶处理后,随着Li含量的增加,合金中14H型长周期堆垛有序结构相(LPSO)的形成受到抑制,同时纳米/亚微米(Mg,Zn)₃Gd颗粒相大量析出,当Li为7.6at. %时合金中无LPSO形成。经热挤压变形后,合金中块状14H相发生扭着分层开裂、层片状14H相发生不同程度溶解、(Mg,Zn)₃Gd相破碎细化、基体发生不同程度再结晶;不加Li的Mg_96.5Gd_2.5Zn₁表现出最佳的力学性能(UTS=325,δ=9.5%),而含Li合金则随Li含量的增加,力学性能逐步下降。合金在不同条件下的组织转变机理及力学行为变化被进行了分析。     

锆元素对Mg_(97)Y_2Zn_1镁合金微观组织和力学性能的影响(英文)

研究锆元素对Mg97Y2Zn1镁合金微观组织和力学性能的影响。锆元素的添加可以细化铸态Mg97Y2Zn1合金的组织。在挤压过程中,Mg97Y2Zn1镁合金在原始晶界和第二相周围优先形核。锆元素的添加促进合金的再结晶过程,这是因为锆元素的添加使合金形成更多的晶界,从而提高了再结晶的形核率。此外,锆元素的添加还能够提高合金的强度和伸长率等力学性能。     

Mg_(65)Cu_(25)Y_(10)块体非晶合金的晶化组织(英文)

将普通铜模浇铸法制得的Mg65Cu25Y10块体非晶合金试样置于200°C进行保温处理,对处理后的试样的相组成和显微组织进行研究。XRD分析结果表明,该块体非晶的晶化随保温时间的延长趋于完全,在此过程中有Mg2Cu、Mg24Y5和HCP-Mg等晶体相析出。通过SEM观察到雪花状组织,EDS结果表明该雪花状组织的成分接近于铸态合金的成分,TEM分析表明其为层片状结构。电子衍射花样分析表明,雪花状组织由Mg24Y5晶体和非晶相组成。在保温过程中,基体中的FCC-Mg会转变为HCP-Mg。     

CO2 laser cut quality of 4130 steel

Samples of 4130 steel were cut on a CO₂ laser cutting system and the combined effects of power and feed rate on kerf width, surface roughness, striation frequency and the size of heat affected zone (HAZ) have been studied. Regression analysis was used to develop models that describe the effect of the independent process parameters on laser cut quality. For the range of operation conditions tested, it was observed that power had a major effect on kerf width and size of HAZ, while feed rate affects were secondary. On the other hand, surface roughness and striation frequency were affected most by feed rate. At low power levels, the smallest kerf width and HAZ are obtained and the effect of feed rate is moderate. Low feed rates gave good surface roughness and low striation frequency. For optimum cut quality, kerf width, HAZ and surface roughness are kept at a minimum. However, operating conditions that satisfy these requirements while maintaining high productivity could not be identified.     

Microstructure and mechanical properties of ultrafine grained Mg97Y2Zn1 alloy processed by equal channel angular pressing

The Mg₉₇Y₂Zn₁ alloy processed by equal channel angular pressing (ECAP) has been investigated. It was found that the blocks of secondary phase were broken into uniform distributed sections after ECAP. The Mg₉₇Y₂Zn₁ alloy processed by ECAP obtained ultrafine grains and exhibits excellent mechanical properties. The average grain size of about 330 nm, yield strength (YS) of 400.3 MPa and ultimate tensile strength (UTS) of 450.0 MPa were obtained by two-step ECAP of 4 passes at 623 K and 2 passes at 603 K. The long-period stacking (LPS) structures contribute to the formation of ultrafine grains in ECAP processed Mg₉₇Y₂Zn₁ alloy. The results demonstrate that ECAP instead of rapid solidified powder metallurgy (RS/PM) can refine grain size and enhance the strength of Mg₉₇Y₂Zn₁ alloy. It was also found that the elongation of alloy is decreased with increasing pass number. It was found that cracks were preferentially initiated and propagated in the interior of X-phase during the process of ECAP.