机械球磨对Ti/Al混合粉末组织和热稳定性影响的研究

为了探索一种制备高综合性能TiAl基金属间化合物的新方法，研究了机械球磨对Ti、Al粉末微观组织及其热稳定性的影响，结果表明，在机械球磨的作用下Al粉末晶粒以高于Ti的速率细化，最终形成局部含少量Ti 纳米晶的非晶，但在整个过程中未发现Ti、Al元素相互扩散形成Ti-Al金属间化合物中间相；不同球磨时间作用下的Ti/Al粉末中贮有不同的能量，且随时间的延长而增加，以非晶化粉末最为显著，内能的增加是由于机械合金化过程引入了大量的微观缺陷所致，对不同球磨时间的粉末进行热处理显示，球磨时间的增加可大幅度降低形成Ti-Al金属间化合物的温度，球磨75h的复合粉末甚至在350℃，保温1h即可转变成金属间化合物。     

放电等离子烧结W-Ni-Fe合金的显微组织与性能研究

采用高能球磨机制备了不同球磨时间的W-Ni-Fe高比重合金粉,采用XRD分析了粉末相的变化.应用放电等离子烧结技术制备了W-Ni-Fe合金.采用SEM和EDX对烧结合金的形貌、断口和成分进行了分析,并且用维氏硬度计测量了样品的硬度.结果表明,球磨20h的SPS W-Ni-Fe合金具有较好的显微组织,断裂方式表现为W晶粒的穿晶解理断裂和粘结相的穿晶延性断裂特征,并且具有较高的硬度.     

AgSn18SbTe20无铅中温热电材料的粉末冶金法制备工艺及其对性能的影响

研究了制备p型AgSn₁₈SbTe₂₀无铅热电材料的机械合金化(MA)结合放电等离子烧结(SPS)工艺, 调查了MA过程中球磨时间和SPS温度对材料电热传输性能和热电优值的影响, 分析了样品的物相和显微结构。研究表明, 适当延长球磨时间和降低烧结温度, 可以有效提高材料的热电性能。优化制备条件可以实现59%的性能提升, 最佳条件(球磨12 h、SPS温度743 K)下制备的样品ZT值在723 K达到0.62。     

机械合金化和放电等离子烧结制备NbMoCrTiAl高熵合金

研究了球磨转速、球料比和球磨时间对NbMoCrTiAl高熵合金粉末的物相、微观形貌及粒度的影响,探讨了不同温度下放电等离子烧结制备NbMoCrTiAl高熵合金微观组织和硬度的变化规律。结果表明:在转速300 r/min和球料比10∶1条件下,球磨60 h粉末只达到部分合金化;在转速300 r/min和球磨50 h时,球料比要达到12∶1才能实现粉末完全合金化;在球料比10∶1和球磨50 h条件下,球磨转速要高于400 r/min才能获得单一BCC固溶体高熵合金。NbMoCrTiAl粉末在高能球磨中元素发生合金化的先后顺序为Al→Ti→Cr→Nb→Mo。NbMoCrTiAl高熵合金粉末在放电等离子烧结(SPS)时发生了第二相析出和溶解转变。随着烧结温度的升高(1 400～1 600℃),第二相的数量减少及其尺寸增大,导致了合金硬度的降低。     

机械球磨Al-64wt.%Ti混合粉末的微观结构和热稳定性研究

本文研究了机械球磨方法制备的Al-64wt.%Ti混合粉末的微观结构和热稳定性.X射线衍射谱(XRD)研究结果表明,经过140h的球磨作用,形成了hcp相的亚稳态Ti(Al)超饱和固溶体;然后对粉末压坯进行固态反应烧结,最终的平衡产物是AlTi和Ti3Al,并用Miedema模型计算并比较了各竞争相的热力学结果..     

球磨法制备Mg基非晶合金及其热稳定性

采用机械合金化法制备了Mg65Cu25Gd10非晶粉末,并研究了球磨的转速、球料比和球磨时间等工艺参数对非晶形成的影响.研究表明当球料比为20∶1,转速为200r/min时较为合适,形成非晶所需的最短时间为40h.采用差示扫描量热仪(DSC)研究了球磨得到的非晶粉末的热稳定性,得到了热力学参数玻璃转化温度Tg、开始晶化温度Tx,过冷液相区宽度ΔTx和晶化焓ΔH等,并将其与熔炼法获得的样品进行对比,发现其热力学参数不受工艺过程的影响,仍然具有很好的热稳定性.同时,用Kissinger方程式对非晶粉末的晶化动力学进行了计算,得到了Tg和Tx的表观激活能.     

球磨时间对MA-SPS法制备FeCoCrAlNiB高熵合金微观结构、硬度和断裂韧性的影响

采用机械合金化(MA)和放电等离子烧结(SPS)相结合的方法制备FeCoCrAlNiB高熵合金。研究球磨时间(1、5、10、20、30和40 h)对合金相成分、微观结构、硬度和断裂韧性的影响。结果表明:高能球磨过程中各金属元素的合金化顺序为Al→Co→Ni→Fe→Cr；混合粉末球磨20 h后基本形成了单一的BCC固溶体相,其颗粒尺寸约为20 μm。对不同球磨时间的混合粉末进行SPS烧结,获得的FeCoCrAlNiB高熵合金主要由无序BCC+B2(Al-Ni)固溶体相和硼化物相(Fe₂B等)组成。随着球磨时间的延长,合金中硼化物相含量先减少后增加并主要以网状形式分布,BCC相含量则与之相反；合金硬度随球磨时间的延长逐渐提高,主要是因为合金元素间固溶程度越来越高,硼化物相逐渐增多；但硼化物形成的网状结构会破坏基体的连续性,导致合金断裂韧性逐渐降低。当球磨时间为20 h时,获得的FeCoCrAlNiB高熵合金的维氏硬度(HV)为(10.9±0.2) GPa,断裂韧性(KIC)为(4.4±0.2) MPa·m^1/2,表现出最优的综合性能。     

机械合金化与放电等离子烧结制备Fe-Fe3Al材料

为开发新型金属材料,采用机械合金化与放电等离子烧结的方法制备Fe-Fe3Al合金.根据Fe-Al二元相图与研究经验,对成分及工艺进行优化设计.用X射线衍射仪(XRD)对成分进行了定性分析,用扫描电子显微镜(SEM)观察了样品的表面与断口形貌,进行了能谱分析,并测试了致密度、显微硬度(HV)及抗弯强度、抗拉强度等力学性能.结果表明:对粉末进行预球磨,并在球磨前后对粉末进行搅拌混合处理,能更好地促使Fe与Al在高能球磨的过程中反应;经放电等离子烧结能够制备出Fe3Al/Fe两相材料,相对密度为99%以上,硬度为HV561,抗弯强度1426 MPa,抗拉强度640 MPa,力学性能优于文献报道的值.     

机械球磨-热压法制备Bio.5Sb1.5Te3热电材料

用机械球磨-热压法制备了Bi0.5Sb1.5Te3热电材料,分别研究了机械球磨时间对合成Bi0.5Sb1.5Te3合金相的影响和烧结温度对其热电性能的影响.结果表明Bi、Sb、、Te原始混合粉末高能球磨10 h以后,就可以完全合金化,生成Bi0.5Sb1.5Te3相.球磨10h的粉末分别在400、450和520℃下热压烧结成型,烧结样品的密度随烧结温度的增大而增加,Seebeck系数和电阻率随烧结温度的升高而降低     

机械合金化制备Nd60 Fe20 Al10 Co10非晶粉末的研究

利用机械合金化制备Nd60Fe20Al10Co10非晶粉末，采用X射线衍射(XRD)和振动样品磁强计(VSM)研究Nd60Fe20Al10Co10非晶的形成过程、磁性能变化及其与成分结构的关系。结果表明，90min后Al原子溶入Nd原子形成固溶体。球磨2h后出现少量非晶，20h后Co单质和Nd单质消失．组织为非晶相(含少量的α-Fe)。球磨100h最终得到非晶 少量的α-Fe纳米晶。球磨过程中，矫顽力随着合金中非晶的量增加而升高．球磨20h矫顽力达到43kA／m。Nd60Fe20Al10Co10合金具有硬磁性是由于非晶相的存在而造成的。     

TiAl纳米合金的机械活化-放电等离子原位烧结

（Ti-50％（原子分数）AD-10％Al2O3粉体经过球磨的机械活化（MA）后，用放电等离子烧结（SPS）工艺，在烧结的同时进行固化。采用机械活化-放电等离子烧结（MA—SPS）的方法原位烧结制备TiAl—Al2O3块体纳米材料。球磨前后，（Ti-50％（原子分数）AD-10％Al2O3粉体的衍射图（XRD）相似。MA后得到晶粒度〈25nm的纳米粉体，其中Al2O3起到机械活化和细化晶粒的作用，促使粉体快速纳米化。纳米粉体在温度低于800℃、烧结时间〈5min的烧结参数下，烧结成TiAl纳米合金。TiAl纳米合金的微观结构表明，合金有γ-TiAl和α2—Ti3Al双相组织。SPS原位烧结后，得到密度为3．73g／cm^3的（γ＋α2）双相组织，组成相的晶粒度〈130nm。     

Fabrication of Ti–Nb–Ag alloy via powder metallurgy for biomedical applications

Ti and some of its alloys are widely used as orthopedic implants. In the present study, Ti–26Nb–5Ag alloys were prepared by mechanical alloying followed by vacuum furnace sintering or spark plasma sintering (SPS). The microstructure and mechanical properties of the Ti–Nb–Ag alloys were investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM) combined with energy-dispersive X-ray spectroscopy (EDX), compressive and micro-hardness tests. The effect of different sintering methods on the microstructure and properties of Ti–Nb–Ag alloy was discussed. The results showed that the titanium alloy sintered by vacuum furnace exhibited a microstructure consisting of α, β and a small amount of α″ martensite phase; whilst the SPS sintered alloy exhibited a microstructure consisting of α, β and a small amount of α″ martensite phase, as well as a nanostructured Ag homogeneously distributed at the boundaries of the β phases. The Ti–Nb–Ag alloy sintered by SPS possessed fracture strength nearly 3 times of the alloy sintered by vacuum furnace.     

Sintering behavior of mechanically alloyed Ti-48Al-2Nb aluminides

Ti-Al intermetallics have been produced using mechanical alloying technique. A composition of Ti-48Al-2Nb at % powders was mechanically alloyed for various durations of 20, 40, 60, 80 and 100 h. At the early stages of milling, a Ti (Al) solid solution is formed, on further milling the formation of amorphous phase occurs. Traces of TiAl and Ti₃Al were formed with major Ti and Al phases after milling at 40 h and beyond. When further milled, phases of intermetallic compounds like TiAl and Ti₃Al were formed after 80 hours of milling and they also found in 100 h milled powders. The powders milled for different durations were sintered at 785°C in vacuum. The mechanically alloyed powders as well as the sintered compacts were characterized by XRD, FESEM and DTA to determine the phases, crystallite size, microstructures and the influence of sintering over mechanical alloying.     

Microstructure and mechanical properties of ultra-fine grained MoNbTaTiV refractory high-entropy alloy fabricated by spark plasma sintering

The MoNbTaTiV refractory high-entropy alloy(RHEA) with ultra-fine grains and homogeneous microstructure was successfully fabricated by mechanical alloying(MA) and spark plasma sintering(SPS).The microstructural evolutions,mechanical properties and strengthening mechanisms of the alloys were systematically investigated.The nanocrystalline mechanically alloyed powders with simple bodycentered cubic(BCC) phase were obtained after 40 h MA process.Afterward,the powders were sintered using SPS in the temperature range from 1500 ℃ to 1700 ℃.The bulk alloys were consisted of submicron scale BCC matrix and face-centered cubic(FCC) precipitation phases.The bulk alloy sintered at 1600℃ had an average grain size of 0.58 μm and an FCC precipitation phase of 0.18 μm,exhibiting outstanding micro-hardness of 542 HV,compressive yield strength of 2208 MPa,fracture strength of 3238 MPa and acceptable plastic strain of 24.9% at room temperature.The enhanced mechanical properties of the MoNbTaTiV RHEA fabricated by MA and SPS were mainly attributed to the grain boundary strengthening and the interstitial solid solution strengthening.It is expectable that the MA and SPS processes are the promising methods to synthesize ultra-fine grains and homogenous microstructural RHEA with excellent mechanical properties.     

Activated sintering of tungsten alloys through conventional and spark plasma sintering process

The sintering temperature of pure tungsten can be reduced through the addition of small amounts of transition elements. The present study deals with the activated sintering of tungsten with 1.0?wt% additions of copper, cobalt, molybdenum, iron and nickel using the spark plasma sintering (SPS) technique. The alloys were sintered at 1200°C and the mechanical properties and microstructures were compared with those of conventionally sintered alloys, sintered under vacuum condition. The high-rate sintering of SPS has led to an overall reduction in process time and also to a better densification of alloys compared with the conventional sintering process. In both the processes, nickel addition is found to be the best activator, followed by cobalt, iron, molybdenum and copper. The addition of copper and molybdenum showed only a meager increase in the relative density. The alloys, with nickel, cobalt and iron additions, sintered through the SPS process offered much higher density compared with the conventionally sintered alloys. The highest density is observed for the nickel-doped tungsten alloy, which is found to be around 90% of the theoretical density. The microhardness of the sintered alloys is found to depend on its sintered density.     

Ti-Al-Al2O3纳米粉体的机械活化-放电等离子烧结

TiAl基合金是很有发展潜力的高温结构材料,为实现快速高效制备此材料,采用新型的机械活化-放电等离子烧结(MA-SPS)制备纳米材料的有效方法,原位制备Ti-Al金属间化合物Ti-47%Al-10%Al2O3(Al为原子分数,Al2O3为质量分数)材料.介绍了放电等离子烧结这种新兴的纳米固体材料制备技术的特点,结合Ti-Al基合金的具体制备工艺,对MA-SPS的特征予以详细分析研究.通过X射线衍射、扫描电镜、透射电镜等分析,经机械球磨活化后,得到晶粒度小于24 nm的纳米单质元素粉体,为后续原位烧结提供合适的烧结原料.其中添加的Al2O3起到细化晶粒、促进纳米化和机械活化、提高出粉率等作用.纳米粉体在合适的参数下经放电等离子烧结后,可得到致密度达98.7%的(TiAl Ti3Al)理想双相组织,其成分的晶粒度小于91 nm,成为纳米固体材料.     

放电等离子烧结制备块体非晶合金研究进展

非晶合金又称“金属玻璃”,是由于超快速冷却凝固导致无法有序排列结晶,从而得到的一种长程无序结构。这种非晶合金与存在晶界和位错的普通合金相比,具有更加优异的力学及物化性能。由于粉末状或条状非晶合金在尺寸和性能等方面的限制,因而大尺寸、优异力学性能及软磁性能卓越的块体非晶合金的制备受到了大量关注与探究。放电等离子烧结技术以温度低、效率高、时间短及冷却速率快等优点,被认为是一种具有广阔发展前景的制备方法。对Fe基、Zr基、Al基及Ti基本身的特点,以及通过放电等离子烧结技术制备不同体系块体非晶合金的物理及化学性能的研究进行了较为全面的综述。概述了放电等离子烧结技术的原理及在制备块体非晶合金方面的优势;分析了放电等离子烧结技术和制备的块体非晶合金材料存在的问题,以及采用该技术制备块体非晶合金的发展前景。重点介绍了在采用该制备不同体系的块体非晶合金时,如何通过改变放电等离子烧结参数,或通过再加工、本身粉末添加元素等方法获得大尺寸、优异性能的块体非晶合金。     

Densification Behavior and Wear Response of Spark Plasma Sintered Iron‐Based Bulk Amorphous Alloys

In the present study, spark plasma sintering (SPS) process is used to sinter Fe‐based bulk amorphous alloys from starting amorphous powder. The sintering was performed in supercooled liquid region (at 630 °C with uniaxial pressure of 70 MPa) where plastic flow of the amorphous powder results in better densification without crystallization. To study the crystallization behavior and its influence on mechanical behavior, the sintered discs were de‐vitrified by annealing at 700 and 800 °C. Detailed characterization of phase development, microhardness at different loads, and wear behavior of the as‐sintered and annealed alloys is presented.     

SiC-ZrO2(3Y)-Al2O3纳米复相陶瓷的力学性能和显微结构

本文介绍用非均相沉淀方法制备的纳米ＳｉＣ－ＺｒＯ２（３Ｙ）－Ａｌ２Ｏ３复合粉体经放电等离子超快速烧得到晶内型的纳米复相陶瓷,超快速烧结的升温速率为６００℃／ｍｉｎ,在烧结温度不保温,迅即在３ｍｉｎ内冷却至６００℃以下。     

放电等离子烧结对TiB_2/AlCoCrFeNi复合材料组织与性能的影响

采用放电等离子烧结方法(SPS),制备体积分数5%TiB_2的等摩尔AlCoCrFeNi高熵合金基复合材料。通过密度测试、X射线衍射、扫描电镜及力学性能测试等方法,研究SPS烧结温度及烧结压力对复合材料的微结构演变与力学性能影响。结果表明:随着SPS烧结温度及烧结压力的增加,复合材料的硬度及抗压强度得到明显提高。在1200℃/30MPa进行SPS烧结后,复合材料的致密度达99.6%,抗压强度达2416MPa,屈服强度达1474MPa,硬度超过470HB。烧结过程中,复合材料的基体高熵合金发生相变,1200℃及30~45MPa烧结时,复合材料由BCC,B_2,FCC,σ及TiB_2相组成。