复合变质处理对铸造热锻模具钢力学性能的影响

研究了变质处理对铸造热锻模具钢力学性能的影响。结果表明：在相同热处理条件下，经RE和RE—Nb复合变质处理后，其冲击韧性与变质处理前相比分别提高了9．7和14．5J／cm^2，常温抗拉强度σb分别提高了82和234MPa，高温抗拉强度分别达到了976和994MPa，而硬度变化不大。     

Cutting force estimation in sculptured surface milling

Cutting force milling models developed up to now are mostly used for planar milling using end-mills. Only a reduced number of models applying ball-end mills have been developed. Furthermore these models usually only consider horizontal surface machining, even though the main application of ball-end mills is sculptured surface machining. This article proposes a model that is able to estimate the cutting forces in inclined surfaces machined both up-milling and down-milling. For this purpose a semi-mechanistic model has been developed that calculates the cutting forces based on a set of coefficients which depend on the material, the tool, the cutting conditions, the machining direction and the slope of the surface.A coordinate transformation has been included in order to consider the slope milling case with different cutting directions.The model has been tested on two materials, an aluminum alloy Al7075-T6 and a 52 HRC tool steel AISI H13. Validation tests have been carried out on inclined planes using different slopes and different machining directions.The results provide errors below 10% in most of the cases and both the value and shape of the predicted forces adjust the measured cutting force.     

MICROSTRUCTURE OF RAPIDLY SOLIDIFIED TiAl ALLOY POWDER

The rapidly solidified powder of Ti-34Al-2Mn alloy was obtained by means of ultrasonicgas atomisation (USGA) technique.The tupical size of the powder is 27 μm.X-ray diffractionresults show that the powder consists of major α_2-phase and minor γ-phase.Under opticalmicroscope both equiaxed and dendritical microstructure features were observed on RS pow-der sections.After annealing at 900 ℃/for 2 h in vacuum,most of α_2-phase transforms intoγ-phase,resulting in refinement of structure.     

BEHAVIOR OF Mg AND ITS EFFECT ON MECHANICAL PROPERTIES OF CAST Fe_3Al ALLOYS

Proper addition of 0.002 wt-% Mg to cast Fe_3Al alloy may obviously improve the room andhigh temperature tensile properties.Auger spectra show that Mg segregates near grainboundaries as very thin layers.Observation under TEM reveals that a suitable amount of Mgenhances ability of cooperative internal deformation so that the dislocations will ease the con-tinuous slip deformation through grain boundaries.The fracture feature of Fe_3Al alloy is oftransgranular cleavage at room temperature and cracks initiate at grain boundaries.     

化合物TbMn6Sn6的磁性和磁相变

采用分子场理论模型对稀土-过渡族金属间化合物的磁性、自旋重取向相变和场诱导的一级磁相变进行了研究.从理论上计算了TbMn6Sn6的易磁化方向随温度的变化以及不同温度时的磁化曲线,描述了自旋重取向相变和场诱导的一级磁相变.基于单离子模型计算了Tb离子和化合物的一阶和二阶磁晶各向异性常数及其随温度的变化,得到了和实验数据基本一致的结果.结果表明:Mn次晶格和Tb次晶格磁晶各向异性能之间的相互竞争是导致自旋重取向相变的物理机制,而稀土离子的四阶晶场项对场诱导的一级磁相变产生很大的影响.     

高强耐磨复杂铝黄铜研究

在生产HA164-5-4-2过程中，解决了Fe、Mn的熔化及均匀化、无缺陷铸锭的生产方法、管材直度控制等工艺关键问题。合金的熔点910、4℃，流点949．2℃，相变热焓114．6J／g；热加工性能优良；在高于550℃时其组织是β相，在低于550℃时其组织是α β相，耐磨颗粒是多元富铁相；力学性能分别为σb=796MPa，σ0.2=675MPa，δ5=20％，IIB=218。同时报道了不同热处理条件下组织和性能的关系。     

铝合金变质处理的现状和发展趋势

本文主要叙述了铝合金变质处理的方法及特点,并对铝合金变质方法的发展趋势作了展望.     

AB INITIO CALCULATION OF THE ELASTIC AND OPTICAL PROPERTIES OF Al_3Sc COMPOUND

The ab initio method has been performed to explore the elastic and optical properties of Al3Sc compound, based on a plane wave pseudopotential method. It can be seen that the calculated equilibrium lattice parameter and elastic constants are in reasonable agreement with the previous experimental data. The elastic constants satisfy the requirement for mechanical stability in the cubic structure of the Al3Sc compound. The optical property calculations show that a strong absorptive peak exists from 0-15eV and a relative small absorptive peak exists around 30eV. The form is caused by the optical transitions between high s, p, and d bands, and the latter results from the optical transitions from high s, p, and d bands to the low 2p band.     

冷镦挤复合的连接成形工艺分析及模具设计

基于镦挤连接成形的金属塑性变形规律,分析了一次连接成形件的冷镦挤复合成形的形变特点和工艺特点,进行了冷镦挤一次连接成形工艺过程的可行性分析设计和模具设计,并得到了生产实践验证。     

WC硬质合金颗粒复合耐磨材料的韧性与断裂

采用不同类型的WC硬质合金颗粒及不同成分的金属基本组成的两种复合耐磨材料，研究了复合材料的韧性及其影响因素，观察分析了其断口形貌及断裂机理．结果表明，复合材料的韧性与断面上WC硬质合金颗粒及金属基体的面积分数有关，主要取决于金属基体的成分、组织状态、韧性和含量，基体的韧性越好，含量越多，则复合材料的韧性越高．在冲击载荷作用下，WC硬质合金的断裂为脆性解理断裂，而金属基体则为具有少量塑性变形的准解理断裂。