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1.
将主烧结曲线(MSC)理论应用于93W-5.6Ni-1.4Fe高比重合金的放电等离子烧结(SPS).以加热速率100℃/min为临界点,建立了2个不同加热速率阶段合金的主烧结曲线.在2个不同加热速率阶段,93W-5.6Ni-1.4Fe高比重合金的放电等离子烧结MSC曲线均可有效预测合金烧结全过程的致密化行为,以及粉末压坯的收缩量和合金的最终烧结密度.计算了93W-5.6Ni-1.4Fe高比重合金放电等离子烧结过程中的致密化函数c,定量地证明了当加热速率大于100℃/min时,随着温度升高,合金的SPS致密化过程显著加快.此外,主烧结曲线理论计算得到的表观致密化激活能与采用Arrhenius公式计算所得到的致密化激活能基本一致.  相似文献   

2.
SPS法制备微米烧结铜及其微观组织演变规律   总被引:1,自引:0,他引:1  
采用放电等离子烧结技术(SPS)在750℃和60 MPa的工艺条件下烧结6 min,制备出了相对密度大于98.5%、平均晶粒度小于3 μm的烧结铜.根据烧结曲线变化特点和特征微观组织,将微米烧结铜的SPS烧结过程划分为4个阶段,即颗粒净化与活化阶段、颗粒接触与烧结颈长大阶段、快速致密化阶段和塑性变形最终致密化阶段,并在此基础上解释了超细粉体的SPS烧结机理.  相似文献   

3.
采用放电等离子烧结(SPS)和超高压力通电烧结(RSUHP)2种快速烧结新方法,对纳米钨粉的致密化行为进行研究。结果表明,采用SPS工艺于1600℃下烧结可获得烧结颗粒结合良好,致密度达97.8%的试样,但晶粒粗化明显;而采用RSUHP方法获得的试样,烧结过程中晶粒几乎不长大,但致密度较低,颗粒间结合较差。将2种方法结合,充分利用SPS的清洁效应和RSUHP的晶粒细化效果,先用SPS在1400℃下预烧结,再由RSUHP二次烧结完成最终致密化,获得平均晶粒尺寸小于400nm,相对密度大于99%的超细晶粒的钨块体材料。烧结过程无需添加任何晶粒长大抑制剂。  相似文献   

4.
微量Y2O3对细晶W-Ni-Fe粉末烧结行为和显微组织的影响   总被引:1,自引:0,他引:1  
采用喷雾干燥-热还原的方法制备纳米级93W-4.9Ni-2.1Fe复合粉末和微量稀土掺杂的复合粉末,研究微量稀土掺杂对烧结致密化和晶粒尺寸的影响.结果表明:微量稀土掺杂能有效地降低该复合粉末的晶粒尺寸,并能改善粉末的分散度;纳米级复合粉末在1380~1410℃液相烧结可实现材料的近全致密化,比同种成分的传统钨合金的烧结温度降低了120℃左右,合金的相对密度可达99%以上;但微量稀土掺杂对烧结的致密化有一定的抑制作用;同时微量稀土元素对合金的晶粒尺寸的抑制作用主要发生在液相烧结阶段.  相似文献   

5.
以微米级的钨粉、镍粉和锰粉为原料,将原料混合均匀后进行放电等离子烧结(SPS)制备90W-6Ni-4Mn合金,探究SPS烧结温度对90W-6Ni-4Mn合金显微组织演变和力学性能的影响。研究结果表明,利用放电等离子烧结(SPS)方法可以在1150~1250°C温度下保温3 min制备出近全致密、综合性能优良的90W-6Ni-4Mn合金。分析合金显微组织,90W-6Ni-4Mn合金组织均匀,平均晶粒尺寸均在10μm以下,主要由钨基相和γ-(Ni,Mn,W)粘结相组成。力学性能测试表明,提高烧结温度,合金的洛氏硬度以及抗弯强度均呈先增大后减小的趋势,在1200°C时其硬度为HRA 68.7,抗弯强度达1162.72 MPa,综合性能最好。  相似文献   

6.
利用放电等离子烧结(SPS)技术对具有相同理论密度的烧结态93W-4.9Ni-2.1Fe和95W-2.8Ni-1.2Fe-1Al_2O_3高密度钨合金进行循环热处理,并通过光学显微镜、SEM、TEM、EDS和三点弯曲实验分析循环热处理对两种合金显微组织和力学性能的影响规律。结果表明:随着SPS循环热处理次数的增加,93W-4.9Ni-2.1Fe合金在平均W晶粒尺寸未发生明显变化的同时,其粘结相中的W含量和位错密度不断升高,合金得到了固溶强化与位错强化,合金的硬度、抗弯强度、断裂挠度等性能相应提高;而对于95W-2.8Ni-1.2Fe-1Al_2O_3合金,由于更高的W含量和Al_2O_3颗粒的加入,烧结态时具有小得多的平均W晶粒尺寸、更大的W-W连接度和高硬脆特性,且SPS循环热处理对其组织和成分分布的均匀性影响程度相对较小,其力学性能虽然随SPS循环热处理次数的增加也得到了一定程度改善,抗弯强度和断裂挠度明显较93W-4.9Ni-2.1Fe合金的低,硬度则明显高于93W-4.9Ni-2.1Fe合金硬度。但循环热处理次数过多,反而会降低两种钨合金的硬度和断裂挠度。  相似文献   

7.
采用机械球磨方法和放电等离子烧结(SPS)技术制备Ti-45Al-7Nb-0.3W(摩尔分数,%)合金。利用XRD、SEM及TEM等分析方法对球磨处理前后粉末的形貌、相组成以及SPS烧结体的显微组织结构进行观察和分析,并研究该球磨合金粉SPS烧结的致密化过程。结果表明:气雾化Ti Al-Nb基合金粉末经球磨处理后,粉末产生大量变形、脆性断裂现象,粉末粒度明显减小;球磨处理使粉末中的β相消失、α相减少、γ相增多。Ti Al-Nb基合金球磨粉在520℃就开始快速SPS致密化过程,在1000℃即可基本达到完全致密;而在500℃加热时,球磨粉烧结热膨胀现象消失,体积收缩明显,这主要与球磨处理后粉末内部大量缺陷引起的回复过程有关。Ti Al-Nb基合金球磨粉SPS烧结体呈现由γ相和α_2相构成的双相组织,并且随着烧结温度的提高,α_2相含量有所增加;球磨处理后,粉末SPS烧结体中α_2/γ片层结构的形成受到抑制。  相似文献   

8.
本文采用流延成型工艺,通过排胶、烧结得到90W-7Ni-3Fe合金板坯,通过冷轧工艺得到厚度小于0.1 mm的90W-7Ni-3Fe薄板材。通过扫描电子显微镜观察实验制得的素坯,混合金属颗粒均匀的分布在粘结剂中。对制得的流延素坯进行综合热分析,制定90W-7Ni-3Fe流延素坯的排胶方案。通过碳硫分析仪测得排胶烧结后的90W-7Ni-3Fe合金板坯残碳量为0.012-0.018 wt%。对不同烧结温度的90W-7Ni-3Fe板坯的组织形貌、相对密度及硬度分析,烧结温度在1450℃时,致密化程度提高,W颗粒相未过大生长,板型保持较好。对烧结后的90W-7Ni-3Fe板坯进行冷轧处理,W颗粒沿轧制方向被拉长成扁椭球状,Ni-Fe相由于塑性比W颗粒好也被沿轧制方向挤压,消除了部分气孔,有效的提高了板坯的致密度及硬度。  相似文献   

9.
针对AlN陶瓷难以烧结致密的特点,采用放电等离子烧结(Spark Plasma Sintering,SPS)技术,利用SPS过程中脉冲电流产生局部高温来加强扩散作用,促进颗粒间颈部接触点形成,并通过添加适量烧结助剂Sm2O3,在短时间内实现了AlN陶瓷的烧结致密化.重点研究了烧结助剂Sm2O3的加入量、烧结温度等工艺参数对AlN陶瓷致密化钩毯统潭鹊挠跋?研究发现Sm2O3的加入使AlN致密化过程提前,烧结温度降低;SPS制备的AlN陶瓷晶粒尺寸均匀一致,晶粒发育良好烧结过程中Sm2O3与AlN粉体表面的Al2O3膜层在晶界处形成Sm-Al-O化合物,该反应有效促进了AlN颗粒间的相互扩散和烧结体的致密,对于AlN晶格完整性的保留非常有利,使AlN烧结体获得了良好的导热性能,其热导率达到150W/(m·K).  相似文献   

10.
采用机械球磨方法制备了含TiB_2的γ-TiAl基合金粉末,并利用放电等离子烧结(SPS)技术制备了其合金粉末烧结体。结合X射线衍射(XRD)和扫描电子显微镜(SEM)分析方法对球磨合金粉末的形貌、相组成及其SPS烧结体的显微组织结构进行观察,分析其致密化及微观组织演化过程,并利用万用拉伸试验机对烧结体的室温力学性能进行测试。结果表明:球磨处理后γ-TiAl基合金粉末呈现近球状和不规则形状粉末;粉末的相组成以α_2相为主,同时含有一定量的γ相和少量的B_2相。提高烧结温度可促进γ-TiAl基合金粉末SPS烧结致密化过程,适量的TiB_2的添加也能够有效降低合金粉末SPS快速致密化的起始温度。当TiB_2添加量为0.2%(质量分数)时,合金粉末在1100℃、40 MPa、10 min条件下烧结,其显微组织呈现出由γ晶、α_2晶和α_2/γ片层结构组成的混合组织结构,各相分布均匀且晶粒细小,其所对应的室温抗拉强度也最高。  相似文献   

11.
采用燃烧法制备10ScSZ粉体,通过等离子放电烧结(SPS)制备10ScSZ细晶致密陶瓷块体。根据SPS上下电极间距随烧结温度的变化绘制烧结曲线,在1200℃附近电极间距最小,判断陶瓷致密化温度在1200℃左右。为验证该方法的可靠性,选取1050,1100,1150,1200,1250℃作为烧结温度分别制备样品。结果表明,在1150℃烧结的10ScSZ样品具有最高的致密度,达到99.4%,且具有平均晶粒尺寸为194 nm的细晶结构,与推测结果基本相符。该实验结果证实了在SPS烧结中通过烧结曲线判断合适的烧结温度是一种高效可行的方法。  相似文献   

12.
Gas-atomized Ti–45Al–7Nb–0.3W alloy powders were consolidated by the spark plasma sintering (SPS) process. The densification course and the microstructural evolution of the as-atomized powders during SPS were systematically investigated by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and electron back-scattered diffraction (EBSD) techniques. As a result of SPS densification, special (α + γ) precipitation zones are formed in the initial stage of sintering, and the residual β phases in the microstructure of the powders are fragmentated. During the following SPS course, α2/γ lamellar colonies at the edge of the precipitation zone, α2 and B2 phase as well as dynamic recrystallized γ grains are found to form. For the as-atomized powders sintered at 1000 °C, the densification is preceded by the early rearrangement of the powder particles and the following formation of sintering necks. For the powders sintered at 1200 °C, plastic deformation plays an important role in densification. Local melting and surface bulging between two adjacent particles can also serve as one of the densification mechanisms. In the later stage of sintering, the growth of sintering necks controlled by diffusion and the pore closure would make important contributions to the densification.  相似文献   

13.
以富硼碳化硼粉体为原料,采用放电等离子烧结(SPS)制备致密碳化硼陶瓷体,研究了SPS工艺对碳化硼陶瓷结构和性能的影响.结果表明,SPS烧结工艺可以低温快速烧结得到致密度达到99.7%的碳化硼陶瓷体,烧结温度和烧结时间对碳化硼的致密度和晶粒尺寸都有影响.烧结过程中样品晶粒表面产生玻璃相,玻璃相的存在使碳化硼断裂机制由穿晶断裂过渡为沿晶断裂,有助于提高材料断裂强度和断裂韧性.SPS制备的致密碳化硅陶瓷材料具有良好的力学性能,其中致密度达到99.6%,抗弯强度达到550.1 MPa,硬度39.52 GPa.  相似文献   

14.
Some works have studied the sintering of TiAl by means of Spark Plasma Sintering (SPS) and it is believed that it is possible to obtain very fine microstructures and very interesting mechanical properties. As raw materials, normally pre-alloyed powders have been used, obtained by atomization or mechanical alloying. However, few works have studied the consolidation of elemental powders. This work presents the synthesis and densification of TiAl-based alloys by means of Spark Plasma Sintering (SPS) using elemental powders as raw materials. The selected composition was Ti–48Al–2Cr–2Nb. The densification process, the evolution of the microstructure with the temperature and the diffusion of the elements (including heavy metals Cr and Nb) are presented. In addition, SPS products are compared with TiAl alloys from elemental powders obtained by conventional methods.  相似文献   

15.
W–20 wt.% Cu powder mixture was mechanically alloyed by high-energy ball milling for various times and the effect of mechanical alloying (MA) on the sintering response of the composite compacts was investigated. The densification, microstructure, hardness and electrical conductivity after solid phase sintering (SPS) and liquid phase sintering (LPS) were examined. It was shown that the microstructure of mechanically alloyed powder profoundly influence the sintering response, i.e. a meaningful relationship between the sintering kinetics and the milling time was observed. It is suggested that MA disintegrates the W–W particle networks and increases the contribution of solid phase sintering (SPS) of nanostructured Cu and W particles on the densification. Higher hardness and conductivity were achieved by prolonged MA and SPS, indicating a lower W–W contiguity of the milled powders compared with the conventionally prepared W–Cu composite. On the other hand, depression of the melting temperature of copper up to 145 °C was noticed by affording a prolonged MA. The lower melting temperature and finer distribution of the Cu particles in the W matrix enhanced the densification during LPS and improved the homogeneity and properties of the final product.  相似文献   

16.
本文采用亚微米WC粉和纳米Co粉、亚微米WC粉和高能球磨后具有纳米晶组织的微米级Co粉这两种具有不同粒径匹配的混合粉末作为原料粉末,利用放电等离子烧结(SPS)技术制备超细晶WC-10Co硬质合金。对不同原料粉末的SPS过程及烧结试样的显微组织和性能进行了系统的对比分析。实验结果表明,以两种混合粉末为原料均获得了平均晶粒尺寸在200nm以下的超细硬质合金材料,其中,采用亚微米WC粉和高能球磨的微米级Co粉利用SPS技术制备的材料相对密度达到98%以上,硬度达到HRA94.5,断裂韧性达到13.50MPa•m1/2,表明具有优良的综合性能。而采用亚微米WC粉和纳米Co粉利用SPS技术制备出的超细晶硬质合金的组织均匀性和性能较差。根据SPS技术的特殊烧结机理,对采用不同粒径匹配和结合状态的WC和Co混合粉末的SPS致密化机制进行了分析。  相似文献   

17.
The excess carbon and oxygen contents of ZrC nano-powders was controlled, and the resultant effects on the densification of ZrC was analyzed. The particle size of the synthesized ZrC powder was about 200 nm and its oxygen content was 0.49 wt%. The good results can be attributed to the rapid heating and cooling rate, the beneficial effects of current, and the relatively low synthesis temperature by using SPS (Spark plasma sintering) for the powder synthesis. The homogeneous distribution between reactants was an important factor to minimize the formation of excess carbon. With increasing the amount of carbon in the raw powder mixture, the oxygen content of ZrC powders decreased and the densification was suppressed. The decrease of excess carbon content, the presence of oxygen in the ZrC lattice, and the fine particle size promoted the sintering of ZrC ceramics without any additives at relatively low temperature and pressure (1750 °C, 40 MPa).  相似文献   

18.
本文采用纳米ZrB2粉体系统研究了ZrB2基超高温陶瓷的放电等离子烧结行为。由于采用纳米粉体,单相ZrB2在1550℃的低温下即发生快速的致密化烧结。ZrB2-SiC陶瓷经1800℃放电等离子烧结后可实现完全致密化,并且材料的弯曲强度高达1078±162 MPa。在1700℃采用放电等离子烧结成功制备了ZrB2-SiC-Cf复合材料,材料断口表现出明显的纤维拔出现象,导致其具有高的断裂韧性值(6.04 MPa·m1/2)和非脆性断裂的模式。同时,ZrB2-SiC-Cf复合材料具有很高的临界热冲击温差(627℃),表明该材料具有优异的抗热冲击性能。  相似文献   

19.
In the current study, the phase evolution of multicomponent equiatomic CoCrCuFeNi, CoCuFeNi, CoCrCuNi, and CoCrFeNi alloys synthesized by mechanical alloying (MA) followed by annealing was studied. From the phase evolution studies, CoCrFeNi, CoFeMnNi, CoCuFeNi, and CoFeNi were chosen to correlate the densification together with phase evolution during spark plasma sintering (SPS). MA resulted in a major face centered cubic (fcc) phase and a minor body centered cubic (bcc) phase in Cr-containing alloys, and a single fcc phase in all other alloys. After SPS, CoFeMnNi and CoFeNi remained as single fcc phase. However, CoCuFeNi transformed to two fcc phases, and CoCrFeNi had a major fcc phase with minor sigma phase. From densification studies, it was evident that CoCrFeNi showed delayed densification, albeit maximum final densification in comparison to other alloys. This behavior was attributed to distinctly different phase evolution in CoCrFeNi during SPS as compared to other alloys. Detailed phase evolution studies were carried out on CoCrFeNi by annealing the powders at different temperatures followed by conventional x-ray diffraction (XRD) and in situ high-temperature XRD of mechanically alloyed powders. The results obtained from the annealing and in situ high-temperature XRD studies were correlated with the densification and alloying behavior of CoCrFeNi alloy.  相似文献   

20.
以氮化铝粉、钼粉为原料,放电等离子烧结(SPS)技术制备了AIN-18%Mo复合陶瓷.通过X射线衍射(XRD)、扫描电镜(SEM)、介电频谱(Dielectric Frequency Spectrum)分析,研究了混料均匀性、渗碳、烧结温度对复合陶瓷致密性、导电性能及介电性能的影响.结果表明,采用特殊混料工艺,制备出Mo均匀弥散分布的复合陶瓷.1700℃、30 MPa烧结复合陶瓷,距离样品表面3 mm以下无杂质相.1450℃烧结复合陶瓷,Mo颗粒呈长条状,电阻率为6.96×102Ω·cm,表现为导体特性;1500℃烧结时样品的电阻率迅速增大为1.81×107 Ω·cm,呈现绝缘体特性:此后随着烧结温度的逐渐增加,样品的电阻率趋于平缓,介电常数、损耗逐渐降低,并从复合材料的显微结构及介电理论对以上结果给予解释.  相似文献   

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