EFFECT OF RARE EARTH ELEMENT Er ON STRENGTHENING OF INTERFACE OF Ti（C，N） BASED CERMETS

ＥＦＦＥＣＴＯＦＲＡＲＥＥＡＲＴＨＥＬＥＭＥＮＴＥｒＯＮＳＴＲＥＮＧＴＨＥＮＩＮＧＯＦＩＮＴＥＲＦＡＣＥＯＦＴｉ（Ｃ，Ｎ）ＢＡＳＥＤＣＥＲＭＥＴＳ￥ＬｉｕＮｉｎｇ（ＤｅｐａｒｔｍｅｎｔｏｆＭａｔｅｒｉａｌｓＳｃｉｅｎｃｅａｎｄＥｎｇｉｎｅｅｒｉｎｇ，...     

Effect of Powder Type and Compaction Pressure on the Density,Hardness and Oxidation Resistance of Sintered and Steam-treated Steels

Two types of Hoganas iron powders—sponge (NC), and highly compressible (SC) were investigated. These specimens were compacted with a pressure of 300, 400, 500, 600, and 700 MPa, before sintering in a production belt-type furnace. Steam treatment of the specimens was at 570 °C for 30 min. The sintered density and as-sintered hardness increase with increasing compaction pressure, and are significantly influenced by the powder structural characteristics. During steam treatment the type of powder and compaction pressure have an important influence on the extent of pore closure and weight gain. The maximum hardness was obtained for the components compacted at a pressure of 500 MPa for both groups of iron powders. Surface pore closure and oxidation resistance of the steam-treated components are improved with increasing compaction pressure.     

Aging behavior of Al2O3 short fiber reinforced Al-Cu alloy composites

Al2O3 short fiber reinforced AI-Cu composites containing 1%, 3%, 5% and 7% Cu were fabricated by a squeeze casting technique. The as-cast Al2O3/Al-Cu composites were solution treated at 535 ℃ and then aged at 170, 190 and 210 ℃, respectively. Age hardening behavior of the Al2O3/Al-Cu composites was analyzed by measuring the hardness of the samples at different aging temperatures and aging time. Microstructures of the composites were observed by transmission electron microscope（TEM）. The results indicate that the hardness of the Al2O3/Al-Cu composites containing 7% Cu is much higher than that containing 1%-5% Cu because of the large amount of CuAl2 precipitant in the Al2O3/Al-Cu composite. With the increase of Cu content from 1% to 7%, the time needed for the appearance of peak hardness shortened, indicating that the addition of Cu can accelerate the kinetic of CuAl2 precipitation in the Al2O3/Al-Cu composites. The Al2O3/Al-Cu composite containing 7% Cu shows the highest increment of hardness by aging treatment. Therefore, in order to get a higher peak hardness, the Al2O3/Al-Cu composites need more Cu addition as compared with the un-reinforced Al-Cu alloys.     

碳对马氏体钢显微组织和力学性能的影响

通过固定其它元素的含量，调整碳含量的方式，研究了碳含量对马氏体钢显微组织和力学性能的影响。结果表明，随碳含量增加，马氏体钢的硬度和抗拉强度提高，但冲击韧度下降。     

碳对马氏体钢显微组织和力学性能的影响

通过固定其它元素的含量,调整碳含量的方式,研究了碳含量对马氏体钢显微组织和力学性能的影响。结果表明,随碳含量增加,马氏体钢的硬度和抗拉强度提高,但冲击韧度下降。     

热处理对铬青铜组织和性能的影响

研究了均匀化处理、固溶时效、冷变形时效等对铬青铜显微组织和性能的影响.结果表明均匀化处理可有效改善铬在铜基体中的分布;铬青铜的最佳固溶工艺为1000℃保温1 h后水淬;较好的时效工艺为470℃×4 h,此时合金的硬度和电导率分别为121.5 HV和79.8%IACS.时效前经适当的冷变形,其硬度为146.7 HV,电导率为85%IACS,和未冷变形直接时效相比分别提高了25.2 HV和5.2%IACS.     

具有梯度结构的涂层硬质合金刀片

研究了Co和Ti(CN)含量对梯度硬质合金的力学性能、梯度结构的影响.测试了梯度硬质合金刀片的切削性能.结果表明:随着合金钴含量的增多,合金梯度层厚度增厚,梯度结构越明显;合金的强度提高,磁饱和提高,磁力、硬度和密度减小.随着合金Ti(CN)含量的增多,合金梯度层厚度有变薄的趋势;随合金的硬度提高,合金的强度和密度减小.切削试验表明:具有梯度结构涂层硬质合金刀片的切削性能比无梯度结构涂层硬质合金刀片的切削性能优良.达到同一磨损高度hB=0.15 mm时,前者的切削寿命较后者提高了近一倍.同时随着合金钴含量的增多,硬质合金刀片的切削性能提高.     

铝合金表面纳米化处理及显微结构特征

采用高能喷丸技术在1420铝合金上制备出纳米晶结构表层,利用X射线衍射仪、透射电子显微镜及高分辨电子显微镜研究由表层沿厚度方向的结构变化特征,并对硬度沿厚度方向的变化进行分析.结果表明:经过表面高能喷丸处理,样品表面形成了厚度约为20μm的纳米晶层,平均晶粒尺寸由约20 nm逐渐增加到约100nm;距表层约20～50 μm为亚微细晶层;表面纳米化的程度与塑性变形量有关;表面纳米化是通过位错滑移的塑性变形方式实现的;与样品的内部相比,表面硬度显著提高.     

磁场深冷处理对合金钢力学性能的影响

对4Cr13、65Mn、60Si2Mn三种工业用钢分别进行了常规淬火、深冷处理和磁场深冷处理，并对经处理后的试样进行了力学性能测试。试验结果表明，深冷处理能提高钢的硬度、强度、冲击韧度和耐磨性，而磁场深冷处理的强韧化效果又明显超过常规深冷处理的。     

Effects of temperature and current density on the surface hardness and tribological properties of Ti-6Al-4V alloy by molten salt carburization

Surface hardening of Ti-6Al-4V alloy was achieved by carburization in a molten salt bath containing BaCO₃ as the carbon-yielding agent with electrolysis within the temperature range 790–930°C. The hardness of the total carburizing layer (TCD) is influenced by the bath temperature, the applied current density and the carburizing period. The major hardening effect is considered to be the formation of a solid solution of carbon in -Ti. The oxide film wrapping at the outermost surface of cathodically charged specimens, identified to be mainly BaTiO₃, was formed irrespective of the bath temperature during the quenching process and has no effect on the surface hardening. The optimal carburizing parameters obtained in this study for surface hardening are carburizing at 930±10°C (bath temperature) and 0.3 A/Cm² (applied current density) for 90 min (carburizing period), while those for tribological properties improvement are carburizing at 860±5°C and 0.3 A/Cm² for 90 min.