粉末加工工艺对银钯合金靶材制备的影响

粉末冶金法制备的银钯合金靶材存在孔隙率较高和相对密度较低的缺点。采用不同的粉末工艺制备了银钯合金粉末样品,使用氢氧含量分析、表面形貌分析、XRD线形分析等方法,探究使用各组样品经真空热压烧结制备的靶材的差异及其机理。结果表明,球磨后的合金粉末在烧结前有必要真空煅烧除氧;随着球磨时间和球磨转速的增加,粉末先细化后形成薄片,烧结体的相对密度先上升后下降;100 r/min球磨2 h所得粉末制备的烧结体具有最高的相对密度,为99.264%。     

机械合金化对Cr-W粉末及烧结材料组织的影响

通过机械球磨法制备原子比为4:1的Cr-W预合金粉末,对球磨后的Cr-W粉末进行XRD、SEM、TEM分析,探讨球磨时间对Cr-W粉末形貌、晶粒大小、组织结构及烧结Cr-W合金固溶度的影响。结果表明：采用机械合金化法,可以制备纳米级的Cr-W预合金粉末;球磨初期,晶粒尺寸、微应变变化较大,48 h后趋于稳定获得小于30 nm的纳米晶粉末;经72 h球磨后,粉末中有固溶体形成;球磨过程伴随着晶格常数的变化;球磨时间越长的粉末,烧结后各相分布越均匀,固溶程度越高     

原始WC粉末粒度分布及球磨时间对超细硬质合金微观结构的影响

分别采用两种Fsss粒度相近、粒度分布差别很大的超细WC粉末为原料,经10～50 h球磨,制备WC-12%Co-1.0%(Cr3C2+VC)混合料,并在1 350、1 410℃和1 450℃下烧结,采用SEM研究两种合金的微观组织结构变化。研究结果表明:采用粒度分布窄的WC粉末为原料,经10 h球磨后烧结,合金中WC晶粒分散均匀,几乎没有WC晶粒粗聚体;而采用粒度分布宽、包含大量团聚体的WC粉末为原料,经10 h球磨、烧结后,合金中含有大量的粗大WC晶粒团聚体,随球磨时间增加,WC团聚体数量、单个团聚体中包含的WC晶粒数量急剧减少,团聚体尺寸不断减小,经50 h球磨才能得到微观结构较为均匀的合金;相同球磨时间下,随烧结温度从1 350℃升高到1 450℃,团聚体尺寸不断增加,团聚体内的形貌也发生明显变化。     

烧结方式对CoCrNi中熵合金组织及力学性能的影响

采用机械合金化法（MA）球磨制备CoCrNi中熵合金原料粉末,结合放电等离子烧结（SPS）或高真空烧结制取CoCrNi中熵合金,研究了球磨时间以及退火对CoCrNi中熵合金原料粉末微观形貌、颗粒尺寸及相结构的影响规律,对不同烧结方式制备的合金块体进行微观结构及力学性能研究。结果表明：随着球磨时间的延长,各单质粉末颗粒尺寸不断减小并逐渐融合,在球磨25 h后,原料粉末主要为fcc固溶体结构,还有少量的bcc相;在后续烧结过程中,少量bcc相发生相转变,组织中只有fcc相结构;退火烧结样品的弹性模量为6.57 GPa,是真空烧结的1.55倍,屈服强度为279.28 MPa,与真空烧结后样品的屈服强度相当,退火烧结的延伸率为35.97%,明显大于直接真空烧结;SPS烧结的块体合金表现出高达793.72MPa的屈服强度和61.08%的塑性应变,且维氏硬度(HV)达到3910.2MPa,与其它2种烧结方法相比,SPS在实现高熵合金（HEAs）快速低温烧结方面更具潜力。     

机械合金化对Fe-Cu-Al热压烧结的影响

本文利用XRD、SEM、DSC等手段研究了Fe-Cu-Al粉末体系机械合金化(MA)过程金属粉体的结构变化及储能情况.将机械合金化处理后的粉末进行热压烧结,并对烧结体进行了金相组织、硬度和抗折强度分析.结果表明,Fe-Cu-Al经MA处理能够形成二元及三元固溶体,粉体粒度和晶粒度明显细化,粉体内储存了大量的表面能和界面能.球磨20 h晶粒度达到稳定值20 nm,粉体储能达到最大值385.1 J/g,球磨30 h粉体粒度达到稳定状态.随着球磨时间的延长,粉末烧结体的成分趋于均匀,组织不断细化.粉末烧结体的硬度在球磨初期显著提高,超过10 h后硬度提高缓慢,而烧结体的抗折强度随着球磨时间的延长几乎成线性增长.球磨50 h粉末烧结体的洛氏硬度和抗折强度分别达到108 HRB和351 MPa.     

γ-TiAl基合金球磨粉放电等离子烧结行为

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。     

机械合金化制备Ni-B-Si合金粉末

本实验选取成分为92%Ni-4%B-4%Si的混合粉末进行机械合金化,并每隔一定时间定量取粉进行SEM、XRD及DSC分析。实验结果表明,当球磨至30 h时,粉末形貌趋于球状,微量元素B和Si已经完全向镍中固溶,此时起始熔化温度降至1038℃;继续延长球磨时间粉末发生团聚,并在球磨至80 h时,趋于非晶化转变;将球磨40 h的合金粉末与松装镍粉在1100℃进行熔渗烧结时,发现其与镍粉发生冶金结合并形成致密的烧结体。     

高能球磨对TiC钢结硬质合金孔隙度影响的研究

采用行星式球磨机对Fe-3.0Cr-3.0Mo-0.5Cu-0.5C-33TiC新型钢结硬质合金混合粉末进行高能球磨,对不同球磨时间粉末形貌及烧结后的合金组织进行观察,测定了烧结后合金的孔隙度。结果表明:球磨初期,粉末粒度迅速减小,粉末出现片状形貌,随着球磨时间增加,粉末粒度减小速度变缓,最后趋于稳定,片状形貌逐渐消失,不规则球形形貌颗粒增多。球磨过程中,在一定时间内,随着球磨时间的增加,混合粉末成分均匀性增加,合金组织细化,孔隙度显著降低。     

TiB_2对γ-TiAl基合金粉末放电等离子烧结行为的影响

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。     

烧结温度对粉末冶金AZ91镁合金组织及硬度的影响

采用球磨法(ball milling,BM)制备了AZ91镁合金粉末,对制得的粉末进行冷压、烧结处理.利用光学显微镜(OM)和扫描电子显微镜(SEM)观察并研究了不同烧结温度下合金的微观组织,利用显微硬度计测试了铸态以及600℃下烧结合金的硬度.结果表明:球磨后粉末由数百微米的不规则颗粒转变为中位径为9.98 μm,且形貌规整的粉末颗粒.随着烧结温度的提高,合金的致密度因内部物质迁移能力的增强而提高,当温度达到600℃时,致密度达到了96.3％.与铸态时相比,粉末冶金法制备的合金,其显微硬度从81.06 HV提高到了104.39 HV.     

Preparation of bulk ultrafine-grained and nanostructured Zn,Al and their alloys by in situ consolidation of powders during mechanical attrition

Bulk ultrafine-grained (UFG) or nanostructured Zn, Al and their alloys were produced via in situ consolidation of powders by mechanical attrition (MA) at room temperature. In situ consolidation of metal powders during MA may be a promising method to produce bulk UFG or nanostructured materials with full density and less contamination.     

High-temperature brazing alloys produced by mechanical alloying

Mechanical alloying (MA) is proposed and tested as an alternative method of producing high-temperature brazing alloys. The oxygen content and distribution in the volume of the particles were determined in the powders of the high-temperature brazing alloy, produced by MA and dispersion of the melt. To reduce the oxygen content, the mechanically alloyed powders of the brazing alloy were refined in nitrogen. The data are presented for the experimental brazed joints produced with high-temperature brazing alloys prepared by MA with or without subsequent refining.     

机械活化热压制备CuCr50触头材料的组织与性能

采用机械合金化（MA）活化CuCr50粉末，然后对MA粉进行真空热压制备出CuCr50触头材料。结果表明，CuCr50MA粉为亚稳态过饱和固溶体，这种过饱和固溶体在随后的热压过程中发生脱溶现象。随脱溶程度的不同，CuCr50块体材料的组织与性能也发生相应的变化。由于MA活化作用，使得CuCr50MA粉在较低的温度保压较短的时间内便获得了致密度高的块体材料，并且第二相cr分布均匀，尺寸细小，其综合性能优于其它工艺方法获得的CuCr50触头材料。     

Microstructure and mechanical properties of FeCoCrNiMn high-entropy alloy produced by mechanical alloying and vacuum hot pressing sintering

FeCoCrNiMn high-entropy alloys were produced by mechanical alloying (MA) and vacuum hot pressing sintering (VHPS). Results showed that the nano-crystalline alloy powders were obtained by MA and the corresponding phase structures were composed of FCC matrices and low amounts of BCC and amorphous phases. After VHPS, the BCC phases almost disappeared, simultaneously with the precipitation of σ phases and M₂₃C₆ carbides. An increase of sintering temperature resulted in grain growth of the precipitated phases. As the sintering temperature was increased from 700 to 1000 °C, the strain-to-failure of the alloys rose from 4.4% to 38.2%, whereas the yield strength decreased from 1682 to 774 MPa. The bulk FeCoCrNiMn HEAs, consolidated by VHPS at 800 °C and 900 °C for 1 h, showed relatively good combination of strength and ductility.     

Thermal Plasma Spheroidization of High-Nitrogen Stainless Steel Powder Alloys Synthesized by Mechanical Alloying

This paper presents the results of experimental studies on the treatment of Fe–23Cr–11Mn–1N high-nitrogen stainless steel powder alloys, synthesized by the mechanical alloying (MA) of elemental powders in the flow of a thermal plasma. Fe–23Cr–11Mn–1N high-nitrogen stainless steel powder alloys were prepared by MA in the attritor under an argon atmosphere. For spheroidization of Fe–23Cr–11Mn–1N high-nitrogen stainless steel powder alloys, the TekSphero 15 plant manufactured by Tekna Plasma Systems Inc was used. The studies have shown the possibility of obtaining Fe–23Cr–11Mn–1N high-nitrogen spherical powders steel alloys from the powder obtained by MA. According to the results of a series of experiments, it was found that the results of plasma spheroidization of powders essentially depend on the size of the fraction due to some difference in the particle shape and flowability, and on the gas regime of the plasma torch. It is established that during the plasma spheroidization process, some of the nitrogen leaves the alloy. The loss rate of nitrogen depends on the size of the initial particles.     

W-Ni-Fe系机械合金化过程中的相变及热力学和动力学研究

W,Ni,Fe粉末按照91.16W6.56Ni2.28Fe的成分配比进行机械合金化(MA)。用XRD确定物相,用TEM(JEM-2000CX型)观察微观形貌和显微结构。并对机械合金化粉末的物相、颗粒尺寸、晶格畸变作了分析讨论。MA可以使W-Ni-Fe系形成纳米晶超饱和固溶体和非晶。参照Miedema半经验理论模型,计算了该合金系的相变驱动力,热力学分析指出该合金系不存在发生非晶化反应的化学驱动力。应用固态反应模型解释了MA过程非晶形成的热力学可能性,在MA过程中,非晶的形成并不绝对要求体系ΔHmix<<0和DB>>DA     

机械合金化与放电等离子体烧结制备TiNiSn基Half-Heusler热电化合物

研究了TiNiSn基Half-Heusler热电化合物的机械合金化(MA)结合放电等离子体烧结(SPS)制备工艺.实验以Ti、Ni、Sn单质粉末为原料,研究了MA和SPS过程中的化学反应与相组成的变化以及所制备的块体材料的电学性能,获得以下主要结果:(1)MA处理后的粉末经过SPS固化后可转变为TiNiSn化合物,但是MA难以直接合成TiNiSn化合物粉末,其原因在于Ni和Sn在球磨过程中较容易生成化合物Ni_3Sn_4;(2)优化MA时间和适量增加Ti的含量有利于提高SPS样品中的TiNiSn化合物含量,本研究获得的TiNiSn相纯度高达90%;(3)最佳条件下制备的TiNiSn化合物块体材料呈n型,测试范围内其功率因子最高可达到1380 mW/m·K~2.     

Phase Evolution and Densification Behavior of Nanocrystalline Multicomponent High Entropy Alloys During Spark Plasma Sintering

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.     

Preparation of W–Al–Mo ternary alloys by mechanical alloying

Single phase W_XAl₅₀Mo_50−X (X = 40, 30, 20 and 10) powders have been synthesized directly by mechanical alloying (MA). The structural evolutions during MA and subsequent as-milled powders by annealing at 1400 °C have been analyzed using X-ray diffraction (XRD). Different from the Mo₅₀Al₅₀ alloy, W₄₀Al₅₀Mo₁₀ and W₃₀Al₅₀Mo₂₀ alloys were stable at 1400 °C under vacuum. The results of high-pressure sintering indicated that the microhardnesses of two compositions, namely W₄₀Al₅₀Mo₁₀ and W₃₀Al₅₀Mo₂₀ alloys have higher values compared with W₅₀Al₅₀ alloy.     

Study of the feasibility of producing Al–Ni intermetallic compounds by mechanical alloying

Mechanical alloying (MA) was employed to synthesize Al–Zn–Mg–Cu alloys of high weight percentage of the nickel component from the elemental powders of constituents via high-energy ball milling. The mixed powders underwent 15 h of milling time at 350 rpm speed and 10: 1 balls/powder weight ratio. The samples were cold-compacted and sintered thereafter. The sintered compacts underwent homogenization treatments at various temperatures conditions and were aged at 120°C for 24 h (T6). The milled powders and heat-treated Al alloy products were characterized via X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS). The crystallite sizes and microstrains of the alloyed powder were estimated via measuring the broadening of XRD peaks using the Williamson–Hall equation. The results have revealed that optimum MA time of 15 h has led to the formation of Al-based solid solutions of Zn, Mg, Cu, and Ni. The outcomes showed that the Vickers hardness of the sintered Al–Zn–Mg–Cu compacts of Ni alloys was enhanced following aging at T6 tempering treatments. Higher compression strength of Al-alloys with the addition of 15% nickel was obtained next to the aging treatment.