放电等离子烧结制备TiAl合金组织和性能

以气雾化工艺制备的Ti43.5 Al5 Nb1 V1 Y(at.％)预合金粉末为原料,采用放电等离子烧结工艺成功制备细晶TiAl合金,研究不同烧结温度(1200～1300℃)对组织和力学性能的影响.通过采用OM,XRD,SEM等方法对烧结试样进行微结构表征,在力学试验机进行室温压缩试验.研究发现,烧结后试样主要有γ-T...     

原料合金化及烧结方式对NiTi合金性能的影响

镍钛形状记忆合金因具有优良的形状记忆效应、超弹性和良好的生物相容性而被广泛地运用于各个领域。本文研究原料粉末合金化及烧结方式对烧结体结构和性能的影响,分别以金属镍/钛混合粉及镍钛合金粉为原料,通过凝胶注模成形得到生坯,再以不同的烧结方式获得NiTi合金,利用X射线衍射仪和扫描电镜等设备,对原料粉末及烧结体的结构和性能进行分析。结果表明:相对于镍钛混合粉,以NiTi合金粉为原料制备出的NiTi合金组织中NiTi相含量更多;采用热等静压方法在1 050 ℃、9 MPa气压值的条件下,烧结4 h,制备出致密度达到91.5%、密度为5.9 g/cm3的合金,比真空烧结制备出的合金的密度值高出约0.5 g/cm3;同时热等静压烧结出合金的平均硬度值为226.2 HV,比真空烧结出合金硬度高出约33.6 HV。采热等静压的烧结方式能促进烧结过程中合金的致密化,大幅度提高凝胶注模成形制备NiTi合金的密度。     

注射成形Fe—2Ni合金的机械性能和微观组织

采用金属粉末注射成形方法制备了Ｆｅ－２Ｎｉ合金试样，制得的试样强度，硬度指标达到了ＭＩＭ协会标准的典型值，而密度，延伸率还有一定的差异，分析了烧结温度，粉末装载量，化学组成和烧结气氛对试样机械性能和微观组织的影响。     

热压烧结制备高Nb-TiAl合金烧结工艺研究

以Ti-45Al-8Nb-0.2B-0.2W-0.1Y元素粉末为原料,采用真空热压烧结工艺制备了高Nb-TiAl合金。结果表明,烧结温度对合金的显微组织影响显著,当烧结温度高于1 350℃时,可制备出致密度高、晶粒尺寸在20~30μm间的全片层组织高Nb-TiAl合金;提高烧结温度可促进Nb在基体相中的扩散,有助于加强Nb的固溶强化效果;合金的室温力学性能与显微组织密切相关,当烧结温度为1 350℃时,其显微硬度为744.5 HV 0.1/15,抗弯强度为674 MPa,显示出较好的室温力学性能。     

多级雾化Cu—Cr—Zr—Mg合金的组织和性能

对多级雾化法制取的Ｃｕ－Ｃｒ－Ｚｒ－Ｍｇ合金粉末热压成形及时效处理后的组织及性能的研究表明：合金粉末经真空封装后,在４２０℃按１０：１的挤压比成形后,合金密度达理论密度值的９８％以上,并且组织中存在着与母相保持共格关系的Ｃｒ相和Ｃｕ５Ｚｒ。经５００℃时效１ｈ后,硬度和导电率分别达ＨＶ１７０及８１％ＩＡＣＳ《     

Micro-Fast中升温速率和烧结温度对零件致密化的影响

采用Gleeble-1500D 热模拟机对316L不锈钢粉末进行烧结,制备出尺寸为Φ1.0mm×1.0mm的微型零件。研究了升温速率和烧结温度对微型零件微观组织及性能的影响。结果表明：随着升温速率的增大,粉末颗粒间孔隙数量减少、试样相对密度增加;随着烧结温度的提高,烧结试样基体孔隙数量减少,试样相对密度显著升高;在升温速率为50℃/s,烧结温度为900℃时,可以得到将近全致密的试样,而且烧结温度低于传统烧结方所用烧结温度;试样最大轴向尺寸变化出现在烧结阶段中,说明在多物理场耦合粉末微成形工艺中升温速率比烧结温度更重要。     

铁硅合金的放电等离子烧结行为

以雾化Fe粉和FeSi合金粉末为原料,采用放电等离子烧结(SPS)制备Fe-6.5%Si高硅硅钢片,通过XRD,SEM等测试手段对样品进行分析。结果表明,铁硅合金的烧结过程可以分为4个阶段;当温度为1 100℃时气孔率为1.48%;烧结过程中主要发生以Fe3Si颗粒为核心反应扩散,烧结初期为颗粒间的紧密结合,烧结中期颗粒的界面处有Fe3Si相生成,形成FeSi过渡层,烧结后期直接形成了Fe(Si)的单一固溶体相。     

颗粒配比对Fe-Cu-C烧结件组织和性能的影响

利用气雾化微米颗粒呈球形的特性,在雾化原料铁粉中添加1%、2%、3%(质量分数)1 000目气雾化铜粉和2%、4%、6%、8%(质量分数)800目雾化铁粉,先后进行混料、压制和烧结制造工序。将烧结制得的试样进行密度、硬度、显微组织测试分析。结果表明,添加3%微米铜粉的样品孔隙率明显减少,组织更加均匀,同时材料的硬度也得到了进一步的提高;烧结后界面之间出现富铜相,有效地对基体粉末颗粒进行了连接。     

Ti-B-C-N粉末烧结的微观组织及其性能

以Ti-B-C-N四元相陶瓷粉末为实验材料,采用真空热压烧结和放电等离子烧结(SPS)工艺对其进行烧结,真空热压烧结和放电等离子烧结温度分别为1900℃和1450℃,烧结压力分别为20 MPa和40 MPa,保温时间分别为1h和3min。使用X射线衍射仪分析试样物相组成,扫描电子显微镜观察试样表面微观形貌和断口形貌,并测试了烧结试样的硬度和抗弯强度。结果表明:真空热压烧结和放电等离子烧结块体的主要生成相为TiB2相和TiCN相,相对密度分别为97.40%和93.06%,热压烧结试样致密度高,颗粒尺寸大,放电等离子烧结试样孔隙较多,晶粒尺寸小;抗弯强度分别为259.98 MPa和335.17 MPa;弹性模量分别为89.11GPa和162.92GPa;洛氏硬度分别为78.8和84.9;放电等离子烧结试样表现出较好的力学性能。     

冷等静压成形及烧结温度对超细WC-TiC-Co 硬质合金性能的影响

采用高能球磨法制备了平均粒度约为550nm的WC-5TiC-10Co超细粉体.研究了冷等静压成形及烧结温度对合金试样性能的影响.结果表明:超细粉体在280MPa、保压2min的冷等静压条件下,压坯密度达到8.13g/cm3且趋于恒定.相同烧结温度下,冷等静压试样的性能优于普通压制试样;随着烧结温度的升高,合金试样的密度提高,硬度和抗弯强度先升高后降低;最佳烧结温度在1450℃左右,试样的密度达到12.08g/cm3,洛氏硬度(HRA)值高达93.6,抗弯强度达到1224MPa.     

TiB2/Cu复合材料组织与性能的研究

以Ti、B和Cu的单质粉末为原料,经混粉-冷压成形-真空烧结,制备出原位自生TiB2陶瓷颗粒增强铜基复合材料.并借助热分析方法和X射线衍射对增强颗粒进行分析,同时通过扫描电子显微镜对复合材料组织进行观察,进一步测定复合材料的力学性能.结果表明,在Ti-B-Cu体系中,通过原位反应生成增强相是TiB2.随着B粉和Ti粉含...     

Study on Squeeze Casting Metal-zirconium Composite Die Material by Hot Press Sintering

ZrO_2-5CrMnMo composite samples were prepared by hot press sintering.When NiCoCrAlY powders were used as the bonding layer and the different mixtures of NiCoCrAlY alloy and 3YSZ (3mol% yttria stabilized zirconia) ceramic powders were used as the transition layers,the connection between zirconia ceramic and 5CrMnMo steel were strengthened.Three composite samples with different structures were fabricated by heat spraying and hot press sintering.Shear and thermal shock cycle tests were conducted to characterize connection strength and thermal shock resistance of these samples.The shear strength reached 95.69 MPa,and the heating shock cycles achieved to the maximum value of 27.7 times.Microstructures and connection interfaces were analyzed by scanning electron microscopy.The hardness and wearing resistance of 3YSZ coat and 5CrMnMo substrate were compared,and the heat insulation property of composite samples were also discussed.It is shown that these composite materials fabricated in this research are benefited to be used as squeeze casting dies.     

Preparation and mechanical properties of β-SiC nanoparticle reinforced aluminum matrix composite by a multi-step powder metallurgy process

β-SiC nanoparticle reinforced A1 matrix （nano-SiCp/A1） composite was prepared by a multi- step powder metallurgy strategy including presureless sintering, hot compacting process and hot extrusion. The microstructures of the as-prepared composites were observed by scanning electronic microscopy （SEM）, and the mechanical properties were characterized by tensile strength measurement and Brinell hardness test. The experimental results revealed that the tensile strength of the composite with the addition of 5wt%/3-SIC nanoprtieles could be increased to 215 MPa, increasing by 110% compared with pure A1 matrix. Comparative experiments reflected that theβ-SIC nanoprticles showed significant reinforcement effect than traditional a-SiC micro-sized particles. The preparation process and sintering procedure were investigated to develop a cost effective preparation strategy to fabricate nano-SiCp/A1 composite.     

Die wall lubricated warm compaction behavior of non-lubricant admixed iron powders

The phenomena of die wall lubricated warm compaction of non-lubricant admixed iron powders were researched, and its mechanism of densification was discussed. Water atomized powder obtained from the Wuhan Iron and Steel Corporation was used. With compacting and sintering, compared with cold compaction, the density of warm compacted samples increases by 0.07-0.22 g/cm 3 at the same pressed pressure. The maximum achievable green density of warm compacted samples is 7.12 g/cm 3 at 120 ℃, and the maximum sintered density is 7.18 g/cm 3 at 80 ℃. Compared with cold compaction, the ejection force of warm compaction is smaller; the maximum discrepancy is about 7 kN. The warm compacted mechanism of densification of iron powders can be obtained: heating the powder contributes to improving plastic deformation of powder particles, and accelerating the mutual filling and rearrangement of powder particles.     

球磨WC-8Co粉末的放电等离子烧结

对WC-8Co粉末不同球磨时间后进行放电等离子烧结,研究了球磨时间及烧结温度对WC-8Co硬质合金微观结构及性能的影响。结果表明:球磨时间延长,粉末颗粒变细,晶格畸变增加,衍射峰强度降低,并随时间延长,团聚现象严重;采用放电等离子烧结,在1 200℃时,可以得到接近全致密的烧结样品,烧结温度低于传统方法的烧结温度;球磨时间在2 h以下时,样品的致密度、硬度和断裂韧性达到最佳,晶粒较小且分布均匀;延长球磨时间,性能显著下降且出现较多粗晶、空洞、Co池等缺陷。     

Microstructure and properties of W-15Cu alloys prepared by mechanical alloying and spark plasma sintering process

W-15Cu composite powders prepared by mechanical alloying （MA） of raw powders were consolidated by spark plasma sintering （SPS） process at temperature ranged 1 230-1 300 ℃ for 10 min and under a pressure of 30 MPa. By using high energy milling, particles containing very fine tungsten grains embedded in copper, called composite particles, could be produced. The W grains were homogeneously dispersed in copper phase, which was very important to obtain W-Cu alloy with high mechanical properties, fine and homogeneous microstructure. The microstructure and properties of W-15Cu alloys prepared by SPS processes at different temperature were researched. The results show that W-15Cu alloys consolidated by SPS can reach 99.6 % relative density, and transverse rupture strength （TRS） is 1 400.9 MPa, Rockwell C hardness （HRC） is 45.2, the thermal conductivity is 196 W/m-K at room temperature, the average grain size is less than 2 μm, and W-15Cu alloy with excellent properties, homogeneous and fine microstructure is obtained.     

Powder Extrusion Molding of Nanocrystalline WC-10Co Composite Cemented Carbide

The rods that were shaped from nanocrystalline WC- 10.21 Co-0.42 VC/ Cr3 C2 （ wt% ） composite powders by using powder extrusion molding （PEM） were investigated. The nanocrystalline WC- 10.21 Co- 0. 42 VC/ Cr3 C2 （ wt% ） composite powders were prepared by the spray thermal decomposition-continuous reduction and carburization technology. In order to improve the properties of rods shaped by using powder extrusion molding, the cold isostatic pressing （CIP） technology was used before or after debinding. Specimens were siutered by vacuum siutering and hot isostatic pressing （HIP）. The density, Rockwell A hardness, magnetic coercivity , and magnetic saturation induction of siutered specimen were measured. The microstructure of the green bodies and the siutered specimens was studied by scanning electron microscopy （SEM）. Results show that the rod formed by using powder extrusion molding after debinding and followed by cold isostatic pressing can be siutered to 99.5% density of composite cemented carbide rods with an average grain size of about 200- 300 nm, magnetic coercivity of 30.4 KA / m, Rockwell A hardness of 92.6 and magnetic saturation induction of 85% . Superfine WC- 10 Co cemented carbide rods with excellent properties were obtained.     

Die wall lubricated warm compaction behavior of non-lubricant admixed iron powder

The phenomena of die wall lubricated warm compaction of non-lubricant admixed iron powders were researched, and its mechanism of densification was discussed. Water atomized powder obtained from the Wuhan Iron and Steel Corporation was used. With compacting and sintering, compared with cold compaction, the density of warm compacted samples increases by 0.07 - 0. 22 g/cm^3 at the same pressed pressure. The maximum achievable green density of warm compacted samples is 7.12 g/cm^3 at 120℃, and the maximum sintered density is 7.18 g/cm^3 at 80℃. Compared with cold compaction, the ejection force of warm compaction is smaller; the maximum discrep- ancy is about 7 kN. The warm compacted mechanism of densification of iron powders can be obtained： heating the powder contributes to improving plastic deformation of powder particles, and accelerating the mutual filling and rearrangement of powder particles.     

3%C-Cu机械球磨复合粉末的烧结

为了给后续的致密化工序（如热挤压）提供较高质量的烧结坯,用扫描电镜和光学显微镜分析了3%C-Cu机械球磨复合粉末所制备烧结坯的显微组织,并研究了工艺参数对其相对致密度的影响规律。结果表明,烧结温度对未机械球磨混合粉烧结行为的影响很大,而机械球磨复合粉对烧结温度不敏感。真空热压烧结可以明显地促进致密化过程。提高烧结温度、延长烧结保温时间或增加热压压强,均有助于提高烧结坯的相对致密度。在相同条件下,烧结坯的相对致密度随着复合粉末机械球磨时间的延长而降低。     

Effect of heat treatment on microstructures and mechanical properties of a bulk nanostructured Al-Zn-Mg-Cu alloy

A bulk nanostructured Al-10.0Zn-2.8Mg-1.8Cu alloy was synthesized by cryomilling first and then by spark plasma sintering (SPS), and the effect of heat treatment on the microstructures and mechanical properties of this alloy were studied. Most MgZn_2 particles with a coarse size lie on the grain boundaries of the SPS-processed sample. After solid solution and artificial aging,fine spherical-like MgZn_2 particles precipitate uniformly in the grain interiors. No obvious grain growth is found after the heat treatment. A nanoindentation study indicates that no clear change is found in the Yong's modulus of the nanostructured alloy after the heat treatment.However, the hardness of the nanostructured alloy increases by about 33% after the heat treatment, which is attributed to the effect of precipitation-hardening.