Ni-Ti合金对Ti(C,N)基金属陶瓷组织和性能的影响

采用粉末冶金方法真空烧结制备了添加Ni-Ti形状记忆合金的Ti(C,N)-Co系金属陶瓷,研究了Ni-Ti合金对Ti(C,N)基金属陶瓷显微组织和力学性能的影响。结果表明:未加Ni-Ti合金的Ti(C,N)基金属陶瓷的显微组织表现为经典的黑芯-灰壳组织,陶瓷相多为球形;而加入Ni-Ti后的金属陶瓷随着Ni-Ti加入量的增多,组织逐渐细化,出现了多边形的陶瓷相,陶瓷相与粘结相的界面呈现直线关系。同时,金属陶瓷的抗弯强度和断裂韧性随着Ni-Ti合金加入量的增多有明显的提高,而硬度基本保持不变;Ni-Ti合金的加入量为15wt%时金属陶瓷获得最好的力学性能。     

大尺寸NiFe2O4-10NiO/17Ni型金属陶瓷惰性阳极的制备

研究以PVA为主要成分的粘结剂体系的热分解特性对大尺寸粉末压坯脱脂行为的影响,发现PVA的不均匀热分解是造成大尺寸粉末压坯脱脂失效的原因之一,开发一种具有稳定热分解反应特性的新型粘结剂体系,实现大尺寸粉末压坯的无缺陷热脱脂;研究烧结气氛、金属相的添加对NiFe2O4-10NiO致密化行为的影响。结果表明：N2气氛烧结及加入Ni可有效提高NiFe2O4-10NiO陶瓷基体的烧结致密度,1350℃时于N2气氛中烧结的NiFe204．10NiO／5Ni型金属陶瓷材料的相对密度达到97．28％。采用优化工艺实现d120mmX140mm深杯状NiFe2O4-10NiO／17Ni金属陶瓷惰性阳极脱脂预烧坯的烧结,所得烧结坯平均相对密度为95．21％。     

Y_2O_3添加对Cu-W合金显微组织和性能的影响

研究了Y2O3添加对Cu-W合金显微组织和性能的影响。结果表明,混合粉末经过裂解、还原后颗粒尺寸得到显著细化。随着Y2O3添加量的增加,烧结试样中钨相尺寸逐渐减小。Y2O3的含量为0.4%时组织中的钨相分布最为均匀,烧结颈形成良好。但随着Y2O3含量的继续增加,钨颗粒自身及Y2O3的团聚倾向均增加,组织中出现孔洞。且Cu-W合金的硬度、电导率均逐渐减小。     

Ni含量和烧结压力对SPS法制备NiTi合金显微组织及摩擦学性能的影响

采用高能球磨和放电等离子烧结法(SPS)在1000℃制备了NiTi合金,研究了镍含量和烧结压力对NiTi合金致密度、显微组织、显微硬度和摩擦学性能的影响。结果表明：通过高能球磨后,粉末颗粒尺寸减小,随着镍含量增加,Ni相衍射峰向高角度偏移。NiTi合金致密度随着烧结压力增大而增大,在低烧结压力下,合金致密度随着镍含量增加从94.7%降低到84.6%;在高烧结压力下,合金致密度随着镍含量增加表现出先增加后减小的趋势,在镍含量为45%(质量分数,下同)时,合金致密度最低。NiTi合金中主要由NiTi相、NiTi₂相和Ni₃Ti相组成,Ni₃Ti相含量随着镍含量和烧结压力增大而增大,并且镍含量和烧结压力增大会引起Ni₃Ti相晶格畸变。随着镍含量从0%增加到65%时,合金显微硬度先增大后减小,在镍含量为50%时,显微硬度最大。在相同化学成分下,合金显微硬度随着烧结压力增大而增大。增大镍含量和烧结压力会降低NiTi合金磨损率,显著提高合金耐磨性。室温下NiTi合金的磨损机制是磨粒磨损和黏着磨损。     

多孔NiTi形状记忆合金的制备工艺

以NH_4HCO_3为造孔剂,利用元素粉末混合烧结法制备了多孔NiTi形状记忆合金。研究了压制压力、烧结温度和烧结时间对多孔NiTi合金孔结构的影响,并分析了其物相组成。结果表明:随压制压力的增加,平均孔径和孔隙率逐渐减小;随烧结温度提高,多孔NiTi合金的平均孔径减小、孔隙率先增加后减少,孔隙分布趋于均匀;随烧结时间延长,多孔NiTi合金的平均孔径及孔隙率先增加后减少。在造孔剂添加量50%,压制压力250 MPa,烧结温度1000℃,烧结时间6 h条件下可制备出孔结构均匀(平均孔径为314μm,孔隙率56.3%)的多孔NiTi合金,其基体相为B2(NiTi)相。     

润滑剂含量不同时W-Ni-Fe合金的温压行为

研究90W-7Ni-3Fe合金的温压成形工艺,探讨润滑剂含量不同时温压行为对硬粉的作用,并比较温压工艺与常温压制工艺的不同。结果表明：在相同单位压制压力下,温压压坯密度明显高于常温压制的;润滑剂含量为0.6%（质量分数）时压坯密度达到最大值,温压压制与常压压制相比,压坯密度增加0.26 g/cm3;润滑剂含量超过0.6%后,压坯密度又逐渐下降;添加润滑剂后合金的脱模力明显降低,其温压脱模力较常压脱模力小;试样的抗拉强度、伸长率在润滑剂含量为0.6%时达最大值,这与烧结体的密度随润滑剂含量的变化一致;同时温压烧结坯的密度与常压试样的区别不明显,但抗拉强度和伸长率都高于同批的常压试样。     

烧结次数对30Mo-ZrO_2金属陶瓷结构及导电性能的影响

采用粉末冶金方法以钼粉和氧化锆粉为原料制备30Mo-ZrO_2金属陶瓷,研究烧结次数对金属陶瓷微观结构和高温电导率的影响。结果表明,烧结次数为3次的试样密度最大(6.41 g/cm~3),高温电导率最高(1 600℃时电导率为12.50×10~(-3)S/cm);增加烧结次数能改变粉体颗粒形态,提高金属陶瓷致密度,降低孔隙率,提高导电相的相对体积分数,增加材料电导率;金属陶瓷电导率随着温度升高而增大,变化幅度随着温度的升高而增加。     

90W-Ni-Fe合金的水基体系凝胶注模成型制备及性能

以工业级钨粉、镍粉和铁粉为原料,采用凝胶注模成型技术制备90W-Ni-Fe合金。研究了分散剂含量和固相体积分数对金属浆料黏度的影响,并对素坯的抗弯强度以及脱脂、烧结进行了分析。结果表明,90W-Ni-Fe金属浆料的黏度随着分散剂添加量的增加先降低后升高,随着固相体积分数的增加而增高。坯体抗弯强度随着单体交联剂比例的增大呈现出先升高后降低的趋势,固相体积分数为45%时坯体的抗弯强度最高。素坯脱脂后在1 445℃烧结1.5 h,获得了密度为16.93 g/cm~3的烧结体,其致密度高达98.72%。     

合金元素P,Cu含量对铸铁短纤维结合剂组织和性能的影响

本文研究了合金元素磷和铜对铸铁短纤维烧结体显微组织和性能的影响。结果表明，合金元素磷可显著提高铸铁短纤维烧结体的密度、致密化系数和压强度。磷与铜的共同加入可进一步提高烧结体的压溃强度和硬度，同时，铜的加入可抑制由磷引起的烧结体的急剧。烧结机理随磷、铜含量的增加逐渐由固相烧结＋瞬态液烧结转变为液相烧结。     

ZrO_2添加量和烧结温度对氧化铝陶瓷性能的影响

采用不同的氧化铝粉为原料,添加ZrO_2,通过冷等静压和烧结工艺制备了致密度较高的氧化铝陶瓷。研究了不同ZrO_2添加量和烧结温度对氧化铝陶瓷的显微组织、烧结性能和显微硬度的影响。结果表明,对于烧结温度为1 600℃和1 550℃的试样,ZrO_2分布在氧化铝晶粒晶界上,显著减少了烧结试样中的气孔。添加ZrO_2降低了烧结温度,提高了烧结试样的致密度,ZrO_2作为第二相也起到了弥散强化的作用。添加ZrO_2可显著改善ZTA复相陶瓷的烧结性能,大幅度提高其相对密度。ZrO_2的加入和烧结温度的提高,均能有效提高试样的抗弯强度。影响试样抗弯强度的因素包括试样的气孔率及试样组分及其性质和微观组织形貌,但试样的气孔率为主要影响因素。提高烧结温度和加入ZrO_2均是通过提高试样的相对密度,降低其气孔率实现力学性能的提升。     

On the Martensitic Transformation Temperatures and Mechanical Properties of NiTi Alloy Manufactured by Selective Laser Melting: Effect of Remelting

In this study, the infl uence of laser remelting on the relative density, martensitic transformation temperatures(MTTs), and mechanical properties of a NiTi alloy fabricated by selective laser melting(SLM) at a laser power between 15 and 75 W were investigated. A relative alloy density of approximately 99% was achieved in the power range of 45–60 W corresponding to the forming energy density range of 65.45–87.27 J/mm~3. The MTTs increased with the increase in the energy density; thus, the initial contents of the B2 and B19′ phases of the SLM-produced NiTi alloy can be tailored by the utilized technique. However, the number of defects such as metallurgical pores and microcracks considerably increased at higher energy densities( 87.27 J/mm~3). Interestingly, the concentration of these defects was reduced by remelting in the energy density range of 21.82–65.45 J/mm~3, while the alloy relative density increased to 99.7% ± 0.1% at a remelting energy density of 65.45 J/mm~3. The results of tensile testing revealed that when the remelting energy was 75% or 100% of the forming energy input, the ultimate tensile strength and elongation of the alloy significantly increased. Therefore, the remelting strategy represents a promising route for manufacturing NiTi alloys with desired MTT ranges and mechanical properties.     

Microstructure and Mechanical Properties of NiTi Shape Memory Alloys by In Situ Laser Directed Energy DepositionEI北大核心CSCD

以Ni粉与Ti粉为原料,采用激光定向能量沉积(LDED)技术制备NiTi形状记忆合金。利用XRD、物相拟合、SEM、EDS和DSC等测试方法,对NiTi合金的显微组织、物相含量和物相转变进行分析,随后采用压缩圆柱样品进行形状记忆效应测试,并评估其形状记忆效应。激光能量密度较低时,NiTi合金中产生大量Ni_(4)Ti_(3)相沉淀,随着激光能量密度增加,Ni_(4)Ti_(3)相消失。激光能量密度为20.0 J/mm^(2)时,NiTi合金具有2878 MPa的压缩断裂强度与34.9%的压缩失效应变,且样品在循环20 cyc后具有88.2%形状记忆恢复率。     

Al_2O_3短纤维/ZA22合金复合材料凝固的方式及组织

采用扫描电镜及能谱仪等测试手段研究了挤压铸造Ａｌ２Ｏ３短纤维增强ＺＡ２２合金复合材料的凝固方式及组织特征。结果表明：在该复合材料中,短纤维呈准二维随机分布,ＺＡ２２合金基体初晶在纤维间隙中生核长大,纤维周围被低熔点物质环绕。压力、纤维及稀土铈的存在均使ＺＡ２２合金组织细化。在复合材料制备过程中,纤维预制块对大块稀土化合物或其它杂质有阻挡作用。     

Effects of aluminum concentration and compact thickness on reaction synthesis of Ni3Al---NiAl alloys

The effects of aluminum concentration and green compact thickness on the reaction synthesis of powder compacts containing 25 to 40 at. %Al were studied under a uniaxial compressive stress of 10 MPa. The results indicate that both reaction product and material density are sensitive to these two parameters. For all powder compacts with a thickness of 5 mm, no temperature increase was detected during reaction synthesis, indicating no formation of transient liquid phases and thus no self-sustaining combustion reaction. For 6- and 7-mm-thick compacts containing 40% Al, a full synthesis reaction took place, resulting in production of the NiAl alloy with a high material density (>98%) and a fine grain size (14 μm). Other compacts containing 25 and 30% Al showed a coexistence of partially and fully reacted zones, with the reaction zone size strongly dependent on aluminum concentration and compact thickness. All the results are discussed in terms of local heat accumulation and heat transfer as well as thermodynamic analyses of exothermic reactions during each reaction step.     

Influence of preparation process on sintering behavior and mechanical properties of ultrafine grained Ti（C, N）-based cermets

The influences of forming and sintering processes on distortion, cracking as well as mechanical properties of sintered bodies of ultrafine grained Ti（C, N）-based cermets were investigated. The results show that lubricant is indispensable to fabrication of ultrafine Ti（C, N）-based cermets, however, with low binder content in powder mixture, the lubrication action of paraffin is attenuated. A appropriate level of 2% （mass fraction） paraffin is determined for a cermet with binder content of 36% （mass fraction）. It is also found that the influence of compaction pressure on distortion and cracking of sintered bodies presents a complex relationship. A relatively lower or higher compaction pressure, less than 100 MPa and more than 400 MPa respectively, favors uniform density distribution in green compact. The heating rate of sintering should be strictly controlled. Too fast heating rate results in enclosed pores to burst and forms large size pores in sintering body. A heating rate of 3 ℃/min is recommended.     

Synthesis and characterization of sol-gel hydroxyapatite coatings deposited on porous NiTi alloys

A hydroxyapatite (HA) coating was deposited onto a porous NiTi alloy via dip-coating using a sol-gel procedure with triethyl phosphite and calcium nitrate as phosphorus and calcium precursors, respectively. Adjusting the concentration and viscosity of the sol as well as changing the spin-coating rotational velocity or dip-coating times, enabled uniform coatings with controllable thickness at the sub-micron scale to be successfully deposited on the external surface and within the pores of the porous NiTi alloy. Cross-sectional SEM analysis and EDS characterization of the HA films show that the coating on the inner surface of the pores is thicker than that on the outer surface. The results of an immersion test in a Tris solution show that the HA coating possesses excellent stability, and the rates of Ni ion release through the HA coatings on the porous NiTi alloys of different porosity ratios in a simulated body fluid decrease markedly compared with the uncoated alloys. There is also a remarkable increase in the apatite forming ability of the HA coated porous NiTi alloy in a calcium containing solution.     

镍钛合金表面钛酸锶生物薄膜的水热合成

目的：改善镍钛合金的耐蚀性和添加锶离子用于治疗骨质疏松症。方法采用氢氧化钠和硝酸锶混合溶液对镍钛合金进行水热处理,处理温度180℃,处理时间分别为1、3和6 h。采用扫描电镜、X射线能谱、X射线衍射和X射线光电子能谱对试样进行显微结构和化学成分分析,采用接触角测量仪评价试样的亲水性,在无钙Hank’s平衡盐液中进行动电位极化实验评价试样的耐蚀性,采用粘结拉伸法测量钛酸锶薄膜与镍钛合金基体之间的结合强度。结果镍钛合金经过水热处理后表面形成了由钛酸锶颗粒组成的薄膜,颗粒尺寸约240~490 nm,薄膜中含有少量镍元素。抛光镍钛试样的水接触角约70°,水热处理试样的接触角大幅上升,达到120°左右。在钝化区内,水热处理3 h试样的阳极电流密度比抛光试样降低了大约一个数量级,因此水热处理试样具有更好的耐蚀性。水热处理3 h制备的钛酸锶薄膜与镍钛基体之间的表观结合强度值为14.1 MPa。结论水热处理不仅改善了镍钛合金的耐蚀性,也在合金表面添加了锶离子,可用于治疗骨质疏松症。     

激光表面重熔NiTi形状记忆合金组织及腐蚀性能

采用2kWNd：YAG激光器对NiTi合金进行表面重熔处理，利用扫描电镜、X射线衍射、X光电子能谱分析重熔层成分和组织结构，利用电化学测试研究重熔层耐腐蚀性能。结果表明：NiTi合金经过激光重熔处理后，可得到致密的重熔层；根据激光处理参数的不同，在重熔层中会出现TiNi、TiNi3等新相，重熔层表面Ti／Ni及Ti^4 /Ti比显著提高；电化学极化曲线表明激光重熔后NiTi合金的耐蚀性得到了显著改善。     

Microstructure characteristics of Ni-43Ti-4Al-2Nb-2Hf alloy prepared by conventional casting and directional solidification

To further investigate the microstructure characteristic and solidification mechanism,so as to provide knowledge for the microstructure control of a NiTi-Al based high-temperature structural material,t...     

自蔓延高温合成多孔NiTi合金孔隙的SVR预测

根据自蔓延高温合成法(SHS)制备多孔NiTi合金孔隙试验所获得的实测数据集,应用基于粒子群算法(PSO)寻优的支持向量回归(SVR)方法,建立不同反应参数(温度,粒度和压坯密度)下合成的多孔NiTi合金孔隙的SVR预测模型,并与基于误差反向传播神经网络(BPNN)回归模型的预测结果进行比较。结果表明：在相同的训练与测试样本集下所获的SVR预测结果的平均绝对百分误差(MAPE)比BPNN预测模型的要小,其预测精度更高,预测效果更好;SVR-LOOCV预测的MAPE也比BPNN略小,且其预测结果的相关系数达到了0.999。因此,该方法是一种预测SHS法制备多孔NiTi合金孔隙的有效方法,可为SHS合成多孔NiTi提供理论指导