放电等离子烧结制备Al-Zn-Mg-Cu纳米晶合金的组织

利用低温液氮球磨和放电等离子烧结工艺制备了块体纳米晶Al-Zn-Mg-Cu合金.采用X射线衍射(XRD)技术分析了材料的晶粒尺寸和微观应变,利用透射电镜(TEM)研究了合金微观组织的演变.结果表明:采用放电等离子烧结法制备的7000系纳米铝合金具有两种不同的纳米晶结构,以晶粒尺寸50~100nm的等轴晶为主,少量200~400nm的大晶粒为辅;烧结过程中发生再结晶及第二相析出,析出的第二相以η(MgZn₂)为主,θ(Al₂Cu)以及S(Al₂CuMg)为辅.     

放电等离子烧结高合金工具钢的组织与性能

本文研究了放电等离子烧结(SPS)参数对HGSF01高合金工具钢致密度、硬度的影响规律,以及烧结态HGSF01高合金工具的显微组织、抗弯强度和摩擦磨损性能。结果表明:材料的致密度随烧结温度的升高和保温时间的延长呈上升趋势,而硬度则是先升高后降低;经SPS得到的材料晶粒细小,晶粒尺寸约为5μm,碳化物颗粒细小、均匀、弥散分布在基体上;烧结态材料的抗弯强度比电渣重熔态材料提高了一倍,耐磨性比电渣重熔态材料略有提高。     

放电等离子烧结TiAl基合金的显微组织及力学性能

以Ti-47.5Al-2.5V-1.0Cr合金粉末为原料,采用放电等离子烧结工艺制备出TiAl基合金,并研究了制备工艺、显微组织与室温力学性能三者的关系.结果表明,采用放电等离子烧结方法可制备出致密度高、组织均匀的TiAl基合金.烧结温度对合金的显微组织影响显著,且其室温力学性能与显微组织密切相关,显微组织越细小,室温强度和塑性越高.当烧结温度为1100℃时,制备出的TiAl-V-Cr合金显微组织类型为细小双态组织,具有35.2%的压缩率和3321MPa的断裂强度,显示出较好的室温压缩性能.     

放电等离子烧结原位制备MoSi_2陶瓷的显微组织与力学性能

以Mo、Si混合粉末为原料,采用放电等离子烧结技术原位制备MoSi_2陶瓷。利用X射线衍射仪、扫描电镜、维氏硬度计、电子万能材料试验机等,研究1 300,1 400和1 500℃下烧结的MoSi_2陶瓷物相组成、微观结构及力学性能。结果表明:MoSi_2陶瓷由MoSi_2和少量Mo_5Si_3/Mo_(4.8)Si_3C_(0.6)及SiO_2组成;随烧结温度升高,第二相Mo_5Si_3/Mo_(4.8)Si_3C_(0.6)含量增多,并发生Mo_5Si_3向Mo_(4.8)Si_3C_(0.6)的相转变;第二相Mo_5Si_3/Mo_(4.8)Si_3C_(0.6)含量增多可细化基体组织,材料沿晶断裂的比例增加,具有一定的强韧化作用;1 500℃烧结的MoSi_2陶瓷综合性能最佳,其致密度为99.5%,维氏硬度为9.8 GPa,抗弯强度和断裂韧性分别为313 MPa和2.9 MPa·m~(1/2)。     

放电等离子烧结制备储氢合金的应用研究现状

介绍了放电等离子烧结制备储氢合金的可行性,从La-Mg-Ni系、Mg基、Ti-V基合金的微观结构及其吸放氢性能等角度综述了放电等离子烧结在储氢合金中的应用研究进展,并指出储氢合金吸放氢性能的改善原因在于适当温度的放电等离子烧结促进了合金中新相的形成,控制了合金晶粒尺寸。     

碳化硅陶瓷的放电等离子烧结

采用添加了Al₂O₃和Y₂O₃助烧剂的碳化硅微粉为原料,通过放电等离子烧结(SPS)技术快速制备了碳化硅陶瓷.分析了材料致密化过程,并重点研究了烧结工艺参数对材料致密度和力学性能的影响规律.结果表明,当SPS工艺参数的烧结温度和压力分别为1600℃和50MPa时,经过5min的烧结,碳化硅陶瓷的致密度可达到99.1%,硬度为HV2550,断裂韧性达8.34MPa·m^1/2,弯曲强度达684MPa.     

放电等离子烧结快速制备高钪含量铝钪合金

采用放电等离子烧结技术制备高钪含量Al-Sc合金,利用扫描电子显微镜、能谱仪和X射线衍射仪等设备对球磨前后Al-Sc合金粉末的形貌、相组成以及不同温度快速烧结样品的显微组织结构进行观察和分析,研究烧结温度对Al-Sc合金显微组织的影响。结果表明:球磨后粉末的形状较规则,其颗粒尺寸为25～45mm,并初步实现了机械合金化,除Al、Sc相以外,有少量Al₃Sc和AlSc₂相生成。放电等离子烧结可实现高钪含量铝钪合金的快速致密化,成功制备出钪含量30%(质量分数)的铝钪合金,通过调整烧结工艺参数,烧结样品的相对密度可达92.19%;当烧结温度高于500℃时,所得样品致密,无孔洞,且无明显晶界;随着烧结温度的提高,Sc相与第二相融合,形成Al₃Sc、AlSc₂等第二相,存在于合金中,且Al₃Sc相呈现逐渐增强的趋势。     

放电等离子烧结制备的细晶铁基材料及其力学性能

采用高能球磨和放电等离子烧结,制备细晶Fe-2Cu-2Ni-1Mo-1C块体材料,在不同温度下对烧结试样进行回火处理,研究烧结温度和回火温度对该合金组织、硬度和横向断裂强度的影响。结果表明:烧结温度对合金密度和硬度影响不大,经650～800℃烧结可得到近乎全致密的铁基合金,相对密度达98%～99%,组织为马氏体、贝氏体、珠光体和残余奥氏体的混合组织,硬度为59～61 HRC。在650℃下烧结时横向断裂强度为2 260 MPa;烧结试样在400～600℃回火4 h,随着回火温度升高,初始烧结组织逐渐向球状珠光体转变,使得合金的硬度逐渐降低,横向断裂强度逐渐升高。经650℃放电等离子烧结和500℃回火热处理后的铁基合金的横向断裂强度最高达3 325 MPa,硬度大于51 HRC。     

石墨烯增强TC4复合材料的微观组织及力学性能

采用球磨法将石墨烯与TC4预合金粉末混合,通过放电等离子烧结工艺在1 200℃制备了石墨烯/TC4复合材料。采用扫描电子显微镜、X射线衍射仪等研究了复合粉末混合前后的形貌和物相结构;采用显微硬度计、Gleeble-3800D热模拟试验机等分析了复合材料的显微硬度和压缩性能。结果表明:通过干法球磨和放电等离子烧结工艺制备的复合材料组织致密,石墨烯与TC4原位生成的TiC在晶界处析出,提高了复合材料的力学性能。复合材料的室温压缩强度和屈服强度,相对于基体分别提高了17.03%和12.5%;硬度和延伸率分别提高了18.2%和60%。石墨烯的加入使得TC4基体晶粒细化,同时与基体反应生成了TiC颗粒,对基体产生了强化效果。     

W-Ni-Fe高比重合金的SPS烧结行为

采用放电等离子烧结(SPS)设备制备了93W-5.6Ni-1.4Fe高比重合金,烧结温度范围为1100~1180℃,保温时间为5min.对不同烧结温度下的样品进行了密度、硬度、抗弯强度等性能测试,采用场发射SEM观察了样品表面形貌及断裂行为.结果表明:采用SPS烧结,可以在较低的温度下实现93W-5.6Ni-1.4Fe高比重合金的固相烧结,使合金致密化,并能有效控制钨晶粒长大,提高材料的硬度、抗弯强度等力学性能.     

Microstructures and properties of CuZrAl and CuZrAlTi medium entropy alloys prepared by mechanical alloying and spark plasma sintering

Equiatomic CuZrAl and CuZrAlTi medium entropy alloys were designed and synthesized by mechanical alloying and spark plasma sintering technique.The alloying behavior,phase evolutions,microstructures and properties of samples were investigated by X-ray diffraction,differential scanning calorimetry,field emission scanning electron microscopy,microscopy/Vickers hardness testing and electrochemical polarization measurement.The results indicate that the final products of as-milled alloys consist of amorphous phases.Ti addition improves the glass forming ability of as-milled alloys.The as-sintered CuZrAl alloy contains face-centered cubic(fcc)solid solution,Al_(1.05)Cu_(0.95) Zr and AlZr_2 phases at different sintering temperatures.With Ti addition,the as-sintered sample is only composed of intermetallics at 690°C,while fcc1,fcc2 and CuTi3phases are formed at 1100°C.CuZrAlTi-1100°C alloy exhibits the highest hardness value of 1173HV0.2owing to the high sintering density,solid solution strengthening and homogeneous precipitation of nano-size crystalline phase.CuZrAlTi-690°C alloy presents a similar corrosion resistance with304 Lstainless steel in seawater solution and further possesses the lower corrosion rate.     

Microstructures and properties of CoCrCuFeNiMox high-entropy alloys fabricated by mechanical alloying and spark plasma sintering

CoCrCuFeNiMox (x values in molar ratio, x?=?0, 0.2, 0.4 and 0.8) high-entropy alloys were prepared by mechanical alloying and spark plasma sintering method. The effects of Mo addition on microstructure and mechanical properties were investigated. The X-ray diffraction (XRD) result showed that the addition of Mo into CoCrCuFeNi high-entropy alloy (HEA) changed the original phase constitution from FCC to FCC?+?σ?+?μ and the peak intensity of (1 1 1) shifted to the left and decreased steadily. The field emission scanning electron microscope confirmed that the Cu-rich second FCC phase disappeared and the σ phase with a tetragonal structure expanded as the Mo content was increased. Additionally, a high density of dimple-like features were seen in CoCrCuFeNi HEA while typical quasi-cleavage facets could be observed from the fracture surfaces of the HEAs with the addition of Mo. The Mo0.8 alloy showed a good wear resistant and appropriate strength with fracture strain 22.70%, fraction coefficient 0.65, hardness 530?HV and compressive strength 1448?MPa.

Special theme block on high entropy alloys, guest edited by Paula Alvaredo Olmos, Universidad Carlos III de Madrid, Spain, and Sheng Guo, Chalmers University, Gothenburg, Sweden.     

Microstructure and properties of CrMnFeCoNi high-entropy alloy prepared by mechanical alloying and spark plasma sintering

The equiatomic ratio CrMnFeCoNi high entropy alloy (HEA) was prepared by mechanical alloying (MA) and spark plasma sintering. This paper reports the behaviour of MA, the phase formation, microstructure and mechanical properties of CrMnFeCoNi HEA. With the increase of milling time, solid solution with single FCC phase was gradually formed. The single FCC phase remained as matrix after SPS at 1373?K and 50?MPa. Ultrafine-grained microstructure and good mechanical properties were obtained: At room temperature, the as-sintered bulks exhibit an excellent combination of high compressive strength (2390?MPa) and high fracture strain (47%).     

SPS烧结M42粉末冶金高速钢的显微组织与性能

采用放电等离子烧结技术(SPS)制备了M42粉末冶金高速钢,研究了SPS烧结M42粉末冶金高速钢及其热处理后的显微组织与性能。结果表明:与普通粉末冶金高速钢相比,SPS烧结制备的M42粉末冶金高速钢显微组织均匀、晶粒细小、无碳化物偏析。经过在1180℃×5min×550℃×1h的热处理后,硬度比普通粉末冶金高速钢提高1～2HRC。     

内燃机用粉末烧结Ti-21.5Nb合金组织与力学性能研究

采用放电等离子烧结技术制备内燃机用Ti-21.5Nb-2Zr-1.2Mo-0.1Y钛合金材料(Ti-21.5Nb), 并对其进行固溶和时效处理, 通过扫描电子显微镜、金相显微镜、X射线衍射仪、万能拉伸测试仪等设备分析试样的微观形貌、组织结构、物相组成以及力学性能。结果表明: 采用等离子旋转电极法制备的预合金球形粉末相对密度较高, 并且未形成孔洞; 烧结试样和固溶试样都是由β相与α相组成, 放电等离子烧结Ti-21.5Nb合金和常规铸锭合金具有相同的相结构变化规律; 合金烧结组织由β等轴晶和一些小尺寸α相构成, 其中β等轴晶的粒径介于30~80μm; 在800 ℃下对烧结试样进行固溶时效处理, 得到的固溶组织主要是由β相构成, 同时在β相中还生成了椭球形α弥散组织; 在500 ℃下对Ti-21.5Nb固溶试样进行时效处理, 在合金基体中析出ω相, 而原先的α相全部消失; 在380 ℃时效处理时, 组织中只存在α相, ω相完全消失; 在800 ℃对Ti-21.5Nb合金进行固溶时效处理可以获得力学性能更优的钛合金材料。     

SPS制备WC颗粒增强高合金工具钢的组织及力学性能

采用放电等离子烧结技术(SPS)制备不同WC颗粒含量的HGSF01高合金工具钢.通过扫描电镜、X射线衍射技术等测试手段研究烧结态的组织、物相组成和力学性能,并对试样的弯曲断裂断口进行分析.实验结果表明:随着烧结温度的提高,材料密度不断提高;随着增强颗粒含量的增加,材料的硬度和抗弯性能得到明显提升,但致密度有所下降;烧结态试样的主相是马氏体,同时还伴有残余奥氏体、Cr7C3、VC、Cr2VC2及少量的Mo、Cr碳化物;由弯曲试验的断口分析得知,1 050℃烧结试样的断口形貌特征为多种断裂机制并存.     

粉末注射成形钛合金的脱脂和烧结性能

应用粉末注射成形技术制备出高精度、高性能的异形钛合金零器件。通过多粒度粉末搭配,采用聚甲醛为主组元的多组元粘结剂,制备出高装载量催化脱脂型钛合金喂料,再经真空烧结获得制品。研究了催化脱脂工艺的影响因素以及喂料配比对烧结性能的影响。结果表明:当大（D₅₀=25.28 μm）、中（D₅₀=16.75 μm）、小（D₅₀=12.66 μm）颗粒按质量比17:6:2搭配时,钛合金混合粉末相对振实密度较大,为55%。喂料较佳的催化脱脂工艺为:脱脂温度120 ℃,N₂通入速率120 cm3·min?1,HNO₃气体通入速率1.5 cm3·min?1,脱脂时间6 h,粘结剂脱除率85%。采用全流程控制杂质含量技术,粉末注射成形钛合金制品的烧结性能可以达到相对密度95.9%,拉伸强度933 MPa,抗弯强度1282 MPa,延伸率7.5%,其中C质量分数为0.10%,O质量分数为0.21%。     

High strength aluminium alloys prepared by nanocrystallisation of amorphous powders using spark plasma sintering

Al based nanocrystalline alloys with high fracture strength are fabricated using consolidation and controlled crystallisation strategy of amorphous powder precursors. The sintered product exhibits high specific strength of 3.18?×?10⁵?Nm?kg^??1. The compacted microstructure and ultrafine grains caused by sufficient densification and crystallisation of Al based amorphous powders are responsible for considerable properties of the sample. Furthermore, the densification process and mechanical behaviour of the sintered Al based nanocrystalline alloy are investigated in detail. The Al based nanocrystalline alloys prepared by synergetic process of powder consolidation and crystallisation of amorphous can exhibit much improved mechanical properties compared with conventional Al alloys, which can have potential engineering applications.