Effect of ion cleaning pretreatment on interface microstructure, adhesive strength and tribological properties of GLC coatings on Al substrates

In this work, a series of ion cleaning procedures (bias and time) were performed on aluminum substrate surface prior to the deposition of graphite-like carbon (GLC) coatings. Special attention has been paid on the interface microstructure, coating/substrate bonding strength and tribological properties. It was found that ion cleaning critically influenced the adhesion and the wear resistance of GLC coatings. The optimization of ion cleaning pretreatment revealed that 400 V/30 min is the best ion cleaning conditions. HRTEM observations on the interfacial region showed that the oxide layer has been removed completely, a strong bonding diffusion interface formed. However, for the low energy ion cleaning (300 V/10 min), TEM observations on the interfacial region between the coating and the Al substrate showed that the oxide contamination still existed. The optimization of GLC layer thickness revealed that the GLC coating with 1 μm GLC layer exhibited the highest critical load and the lowest friction coefficient of 14.7 N and 0.065, respectively.     

Effects of annealing time on microstructure and mechanical properties of MosSi3 alloy

以纯金属Mo和纯Si为原料，采用电弧熔炼法制备了Mo5Si3合金。在1200℃对其进行不同时间真空退火，并对合金的相组成、显微结构及力学性能进行分析。结果表明，随退火时间的延长，合金致密度、显微硬度和抗压强度提高，其压痕断裂韧性表现出先增加后降低的趋势，退火20h后合金断裂韧性为3．23MPa·m^1/2。退火50h后，合金主要物相为Mo5Si3和少量MoSi2，在合金中形成M05Si3／MoSi2层片状组织结构，层片间距在20-50μm之间。M05Si3晶粒尺寸和点阵畸变分别为87．3nm和0．0986％，合金具有纳米晶结构。     

Effect of different treatments on the microstructure and functional and pasting properties of pigeon pea (Cajanus cajan L.), dolichos bean (Dolichos lablab L.) and jack bean (Canavalia ensiformis) flours from the north‐east Argentina

The effect of germination (G; 5 days), soaking‐cooking (SC; 6 h–20 min, 6 h–40 min, 6 h–60 min) and microwave (M; 50%, 70%, 100%) treatments on pigeon pea (PP), dolichos bean (DB) and jack bean (JB) seeds was studied. Microstructure of seeds and functional (protein solubility, water‐holding capacity, oil‐holding capacity, emulsion stability) and pasting properties of flours were determined. Germination and microwave treatments modified the protein matrix of cotyledon cells preserving the shape of the starch granule, whereas the SC treatment (6 h–60 min) affected both. The soaking‐cooking is the most influential treatment on the functional properties of PP, DB and JB flours, as increased water absorption capacity (73–96%), decreased protein solubility (>80%) and the tendency to retrogradation of amylose (69–85%) also improved emulsion stability.     

Evaluation of microstructure and mechanical properties of Mg-xCe-0.5Zn alloys by nano-indentation

The microstructure and mechanical properties of Mg-xCe-0.5Zn(x=0.5,1.5,2.5,molar fraction,%) alloys were examined using a nano-indentation technique.The alloys were fabricated using a vacuum induction melting method under an argon atmosphere. The microstructures of Mg-xCe-0.5Zn alloys mainly consist ofα-Mg and eutectic Mg12Ce phase.The volume fraction and size of the eutectic Mg12Ce phase increase with increasing Ce contents.Nano-indentation test results show that the indentation hardness and elastic modulus of the eutectic Mg12Ce phase are higher than those of theα-Mg matrix.In addition,the mean indentation hardness and elastic modulus of the Mg-xCe-0.5Zn alloys increase with the Ce addition amount increasing.     

Microstructure evolution of semi-solid Mg-14Al-0.5Mn alloys during isothermal heat treatment

A new Mg-14Al-0.5Mn alloy that exhibits a wide solidification range and sufficient fluidity for semi-solid forming was designed.And the microstructure evolution of semi-solid Mg-14Al-0.5Mn alloy during isothermal heat treatment was investigated. The mechanism of the microstructure evolution and the processing conditions for isothermal heat treatment were also discussed.The results show that the microstructures of cast alloys consist ofα-Mg,β-Mg17Al12 and a small amount of Al-Mn compounds.After holding at 520℃ for 3 min,the phases ofβ-Mg17Al12 and eutectic mixtures in the Mg-14Al-0.5Mn alloy melt and the microstructures ofα-Mg change from developed dendrites to irregular solid particles.With increasing the isothermal time,the amount of liquid increases,and the solid particles grow large and become spherical.When the holding time lasts for 20 min or even longer,the solid and liquid phases achieve a state of dynamic equilibrium.     

Cu-Fe基金刚石复合材料的制备工艺及性能

采用真空热压烧结工艺制备了Cu-Fe基粉末金刚石复合材料磨头,通过金相、XRD及硬度测试等实验方法,研究了不同烧结温度下制得的合金材料的显微组织特性和性能。结果表明,在实验条件下,烧结体中各元素之间产生了冶金结合,且合金化程度随着温度的升高而增大;930℃时,烧结体中金刚石与基体结合性较好,金刚石无石墨化现象,烧结体的硬度最高,达到160HB。     

Effect of friction stir processing on microstructure of laser clad cobalt-based alloy

(The microstructural refinement of cobalt-based alloy (Stellite No. 6) by laser cladding and friction stir processing (FSP) was studied. A nanometer-sized microstructure consisting of fine carbide (particle size: 100–200 nm) and a grain (grain size: 150–250 nm) was successfully fabricated by the FSP on the laser clad cobalt-based alloy. The nanostructured cobalt-based alloy (Stellite No. 6) had an extremely high hardness of about 750 HV.     

Creep resistance of as-cast Mg-5Al-5Ca-2Sn alloy

In the present study, creep properties of as-cast Mg-5Al-5Ca-2Sn(AXT552) alloy were investigated by means of a GWT304 creep testing machine at temperatures of 175 °C and 200 °C in the stress range of 35-90 MPa. Results show that creep rates increase with applied stress at an identical temperature. Creep strain at 100 hours is 0.0518% and 0.083% at creep conditions of 175°C/75 MPa and 200°C/60 MPa, respectively, which is comparable to MRI230 D and much lower than most of AX series alloys. By the observation and analysis for samples before and after creep tests using a Shimadzu XRD-7000 type X-ray diffractometer(XRD) and a Hitachi S-3400 N type scanning electron microscope(SEM), it was found that Al_2Ca(C15) phase precipitated out of C36 phase or matrix. The cavity formation and connection at the interface of soft matrix and hard intermetallics caused the propagation of cracking along the eutectic phase during creep process and dislocation accommodated grain/phase boundary sliding is expected to be the dominant creep mechanism.     

铸态贝氏体中锰钢化学成分设计及其性能研究

主要研究铸态锰钢加入适量Mo、V、Ti、RE等元素的显微组织和力学性能。研究结果表明:当化学成分(质量分数)设计为1.0%C,4%Mn,1%Si,钼铁加入量为总重量的1%,钛铁为0.8%,钒铁为0.6%,稀土硅为0.3%,可获得贝氏体组织,并具有较好的综合力学性能,而且在非强烈冲击工况下具有高抗磨性。