WC-Co硬质合金的相组成及其相变

碳化钨（WC）是一种硬度高、热稳定性和耐磨性好的硬质合金材料，WC－Co硬质合金的性能除与WC晶粒的大小有关外，在很大程度上还取决于合金中的相组成及相转变，本文主要依据WC－Co系相图，采用热力学方法对烧结过程中合金的γ,η相的生长条件、成分结构以及相变过程进行了讨论，从本质上阐明WC－Co硬质合金的成相规律和影响因素。     

高能球磨制备纳米WC-8(Fe/Co/Ni)RE硬质合金研究

用高能球磨法及真空烧结工艺制备纳米WC-8(Fe/Co/Ni)RE硬质合金.球磨时间、烧结工艺、稀土添加量对合金性能有重要影响,通过对球磨时间、烧结工艺、稀土添加量等环节的优化控制,在球磨60小时、1430℃烧结、加入Y占Co重量1%情况下,可制备出平均粒度为700nm左右、硬度达90.7HRA的纳米WC-8(Fe/Co/Ni)RE硬质合金.     

Microstructures and properties of WC-20Co-1Y_2O_3 cemented carbide by hot-press and liquid phase sintering

1　INTRODUCTIONInRef .[1],averyinterestingandinexplicablefindingwasreportedthataspecialwhisker likeWCgrainstructure ,mostintherangeof 10 0 2 0 0nmindiameterand 1 2mminlength ,wasformedinWC 2 0Co 1Y2 O3cementedcarbidepreparedbyhot pressbelowtheeutectictemperature .ItwasmentionedinthepaperthatWCpowderwithFisherSubsiereSizer(FSSS)of 1μm ,ultrafineCopowder ,andY2 O3powderof 1μmwereusedastherawmaterialsofWC 8Cocementedcarbide .However ,whetherthesamerawmaterialswereusedinWC 2 0Co …     

Microstructures and properties of WC-2OCo-1Y2O3 cemented carbide by hot-press and liquid phase sintering

Ultrafine tungsten carbide and fine cobalt as well as nano yttrium oxide powders were used as the raw materials. The effects of hot-press below the eutectic temperature and conventional liquid phase sintering on the structures and properties of WC-20Co-1Y2O3 cemented carbide were studied. It is shown that hot-pressed alloy has the character of isotropic properties and microstructure with homogeneous and ultrafine WC grains. However, the ultrafine and fully-densified structure is developed at the cost of the presence of large amount of cobalt-lake (uneven-ly distributed binder phase), and thus lower strength. Yttrium oxide in the alloy cannot play the role of grain growth inhibitor fully when cemented carbide with high content of cobalt and ultrafine raw materials is sintered at high liquid phase sintering temperature. Peculiar platelet-enhanced bi-model structure is formed in WC-20Co-1Y2 O3 cemented carbide by conventional liquid phase sintering, which points out that yttrium oxide in the alloy facilitates the formation of plate-like WC grain.     

Phase composition, transition and structure stability of functionally graded cemented carbide with dual phase structure

The phase composition, phase transition and phase structure transformation of the wire-cut section of functionally graded WC-Co cemented carbide with dual phase structure were investigated by XRD phase analysis. It is shown that the composition of η phase in the core zone is Co3W3C （M6C type）. The structure of cobalt based solid solution binder phase is fcc type. At the cooling stage of the sintering process, the phase transition of η phase, i.e. M6C→M12C and the martensitic phase transition of the cobalt based solid solution binder phase, i.e. fcc→hcp are suppressed, which facilitates the strengthening of the alloy. Because the instantaneous temperature of the discharge channel is as high as 10 000 ℃ during the wire cutting process, the processed surface is oxidized. Nevertheless, the oxide layer thickness is in micro grade. In the oxide film, η phase is decomposed into W2C and CoO, and cobalt based solid solution binder is selectively oxidized, while WC remains stable due to the existence of carbon containing liquid organic cutting medium.     

C-Mn segregation and its effect on phase transformation and deformation in Fe-Mn-C alloys

C-Mn segregation and its effect on phase transformation and plastic deformation in Fe-Mn-C alloys were studied through the calculation of valence electron structure, the microregion composition detection and TEM in-situ dynamic tensile deformation test The experimental results show that in Fe-8Mn-1.2C alloyed austenite, nA of units with C Mn involved is 3 98 times that of units without C involved and 1.4 times that of units with C involved; aCD of units with C-Mn involved is 2 21 times that of units with C involved. In Fe-Mn-C alloyed austenites, there exists microsegrcgation of C-Mn, forming the randomly distributed Fe-Mn-C atomic cluster segregation zone linked with the -C-Mn-C-Mn- strong bond network, which will effectively slow down the motion of atoms and retard the initiation of the slip system and the movement of dislocation, and thus will severely influence the phase transformation and deformation of the alloy     

Effects of C and Mn elements on deformation-enhanced ferrite transformation in low carbon （Mn） steels

Effects of C and Mn contents on the deformation-enhanced ferrite transformation （DEFT） in low carbon （Mn） steels have been investigated by hot compression. The microstructures of 2-4μm ultra-fine equiaxed ferrite grains with minors distributed homogeneously can be obtained by DEFT in all the tested steels. The more pronounced refinement is achieved as the C or Mn content increasing because of the higher-density nucleating sites and lower growth rate. The effectiveness of C on the level of refinement is more obvious than that of Mn.     

酸性矿山废水S(-II)对含铬和钼施氏矿物溶解与相转变的影响

施氏矿物对酸性矿山废水中重金属的环境行为有一定的制约作用,但随着环境条件的改变,施氏矿物可能会溶解并产生相转变,从而引起重金属的再次释放。采用快速化学法合成不同铬、钼含量的重金属负载型施氏矿物,并采用流动柱法结合XRD、SEM及XPS等表征手段探究酸性矿山废水还原性S(-II)对负载不同含量铬和钼的施氏矿物溶解与相转变的影响。结果表明：淋滤液中重金属和硫离子浓度随淋洗天数的增加而下降,并随铬和钼负载含量的增加而明显下降,下降量大小顺序为Sch>0.1Mo0.06Cr-Sch>0.2Mo0.09Cr-Sch,而重金属铬和钼的释放过程以零级动力学模型描述最佳。XRD和XPS表征结果表明：未负载重金属施氏矿物处理组反应后产物主要为针铁矿,而负载的重金属在一定程度上提高了施氏矿物的稳定性,延迟了矿物的相转变。     

低碳钢钢锭急冷层的相变及其对红送裂纹的影响

研究了德ｎＣｒ５齿轮钢锭急冷层的相变,测定了临界点和ＣＣＴ图,发现急冷层形成时,高温δ铁素体在包晶转变时有剩余,其周围包着奥氏体,在钢锭快冷和再加热过程中有独特的组织转变过程和形态,这种组织易于在相变应力下产生显微裂纹,在宏观内应力作用下可能促发钢锭红送裂纹。     

Effect of Dy on Structure and Magnetic Properties of Dy_xFe_(60.5-x)Pt_(39.5) Alloys

Effects of the content of Dy on structure and magnetic properties of DyxFe60.5-xPt39.5 alloys(x = 0, 0.5, 1.0, 1.5) were investigated. The results of XRD analysis proved that the phase-transitional temperature of DyxFe60.5-xPt39.5 alloys from disordered face-centered-cubic structure to ordered face-centered-tetragonal cubic structure decreases with the increase of the content of Dy(x). Suitable content of Dy can improve the exchange coupling between soft magnetic phase and hard magnetic phase by refining gr...     

低活性Fe-Cr-Mn(W,V)合金相稳定性的实验与热力学计算

采用实验和Thermo-Calc热力学计算方法对4种不同成分的Fe—Cr—Mn(W，V)合金(1#、2#、3#、4#合金)的相稳定性进行了研究．实验结果表明，4种合金在623K、673K和773K下时效200h后的主导相为较稳定的奥氏体相．基于热力学自由能的Thermo—Calc计算结果表明：4种合金在实验对应温度下的金相组织为稳定的奥氏体相，计算结果与实验结果有较好的一致性．     

WC和Mo2C添加对Ti(C,N)基金属陶瓷切削性能的影响

传统的Ti(C,N)基金属陶瓷刀具材料广泛采用Mo2C来改善粘结相对硬质相的润湿性,近年来Mo的价格不断上涨,寻找低成本金属代替Mo已成为Ti(C,NEDS)基金属陶瓷的发展趋势。为了探讨WC代Mo2C添加的可行性及其效果,研究了WC和Mo2C添加对Ti(C,N)基金属陶瓷切削性能的影响,采用电子扫描显微镜（SEM）观察刀具的磨损形貌,通过能谱分析（EDS）分析磨损表面的元素分布,并对刀具的主要磨损机理进行分析。实验结果表明,添加WC的金属陶瓷的切削长度和添加Mo2C的相当,将原始WC粉末粒度细化后,不仅切削长度显著增加,切屑也由带状缠乱型变为螺旋型,并且大大减少积屑瘤的形成,有利于切削的进行。切削磨损机理主要为扩散磨损和氧化磨损,伴有轻微的磨粒磨损。     

熔融Ni-(Cr, Co, W)合金的表面张力及偏聚现象

采用改良静滴法测定了熔融Ni-（Cr，Co，W）二元舍金在Ar＋3%H2气氛下1773-1873K温度范围内的表面张力数据，采用Butler方程计算并分析了（Cr、Co、W等组元在合金中的偏聚现象。结果表明，表面张力的计算值和实测值具有良好的一致性，合金的表面张力随着温度的升高而下降。自由电子数目较少，表面张力较小的组元在表面偏聚，溶质元素的原子半径与溶剂元素相比相差越大，舍金熔体的偏聚现象越严重，最终导致Ni在表面富集，而Co、W在合金内部偏聚。     

三（4—氯苯甲酸）纤维素酯的合成及其作为色谱固定相的性能研究

采用催化合成法合成了三（4－氯苯甲酸）纤维素酯;并负载于Gas Chrom Q载体上,用不同类型的探针分子表征其作为气相色谱固定相时的吸附性能,在其固定相上成功地分离了正构醇（C1－C6）。     

Precipitation and Hetero-nucleation Effect of V(C,N)in V-Microalloyed Steel

The precipitation behavior of V(C,N) in steels microalloyed with vanadium was researched using a thermal simulator during single-pass deformation at 800-750 ℃.The V(C,N) precipitates and its nucleation effect on ferrite were investigated by TEM and EDS.The experimental results show that there are two remarkable heterogeneous nucleation effects of V(C,N) particles precipitated before y→αphase change:primary reason is that high coherency between V(C,N) and ferrite promotes V(C,N) to become a nucleating center of intragranular ferrite;secondary reason is that the coarsening of V(C,N) causes locally solute-poor region in austenite,thus expedites the nucleation of intragranular ferrites further.Furthermore,the relationship between the size and shape of V(C,N)was studied,and identification method was provided for distinguishing interphase precipitation and general precipitation to avoid erroneous judgment and misguide.     

High temperature strength and ductility of the （C＋N） strengthening Fe-Cr-Mn（W, V） steels

Fe-Cr-Mn(W, V) austenite steels used as low radioactive structural materials in fusion reactor have been investigated. The resuits show that the high temperature strength and the creep fracture life of Fe-Cr-Mn(W, V) steels can be effectively improved through (C N) complex-strengthening, so can be the high temperature ductility. The strength and ductility of the steels are superior to that of SUS316 steels and JPCAS below 673 K. The relationship between strength, ductility and the formation temperature is related to the evolution of deformation microstructure. The fracture and microstructure observation above 673 K indicates that the main way to further improve ductility at high temperature is the control of carbide coarsening at the grain boundaries.     

q－相干态光场相位特性

本文给出了ｑ变形光场Ｐｅｇｇ—Ｂａｒｎｅｔｔ相位定义，计算了ｑ－相干态，ｑ－奇偶相干态的相位分布函数及相位算符的期特值和相位的涨落，得出ｑ畸变参数决定相位分布函数及相位涨落的值．     

Nd－Fe－B合金中2－14－1相和Nd_2（Fe，Co）_（14）B的研究

研究了Ｎｄ２Ｆｅ（１４）Ｂ和Ｎｄ２（Ｆｅ，Ｃｏ）（１４）Ｂ合金的穆斯堡尔谱和显微组织．主要研究了Ｎｄ２Ｆｅ（１４）Ｂ在５００℃时的显微组织及Ｎｄ２（Ｆｅ，Ｃｏ）（１４）Ｂ中Ｆｅ原子占有概率的穆斯堡尔谱面积对Ｃｏ浓度的影响。     

Microstructure, crystalline phase and electrical properties of Li0.06（Na0.5K0.5）0.94Nb（1-2x/5）MgxO3 lead-free piezoelectric ceramics

MgO-modified Li0.06(Na0.5K0.5)0.94NbO3(L6NKN) lead-free piezoelectric ceramics were synthesized by normal sintering at a relatively low temperature of 1000°C.The crystalline phase,microstructure,and electrical properties of the ceramics were investigated with a special emphasis on the influence of MgO content.The addition of MgO effectively improves the sinterability of the L6NKN ceramics.X-ray diffraction analysis indicates that the morphotropic phase boundary(MPB) separating orthorhombic and tetragonal ph...