马氏体切变学说的评价

到目前为止,材料学界普遍认为马氏体相变是切变过程,有人则认为切变机制是成熟的理论,其实不然．综合分析了1930年以来提出的所有切变机制,指出各切变机制均与实际不符合的缺点,尚未形成普遍成熟的理论,而是切变学说．将新发现的珠光体浮凸,结合贝氏体、马氏体表面浮凸现象,一并分析了浮凸的形成机制,认为形成表面浮凸的主要原因是各相比体积不同,相变时试样表面不均匀体积膨胀所致．表面浮凸是过冷奥氏体转变产物的普遍现象,因而指出马氏体的切变机制缺乏实验依据．马氏体相变中,原子是极为复杂的集体有组织的位移,不是简单的机械式的切变过程．     

粉煤灰保温砌筑砂浆的研究

本文对掺原状粉煤灰的保温砌筑砂浆的配合比及其性能进行了试验研究。试验表明掺加适量原状粉煤灰可提高保温砌筑砂浆的强度     

轴承钢珠光体球化的研究现状及发展趋势

概述了轴承钢球化退火在轴承生产中的作用,分析了珠光体由片层状转变为颗粒状的变化规律,讨论了片层渗碳体的打断、短棒状向颗粒状转变以及颗粒状熟化长大的热力学机制。结果认为珠光体球化工艺的不足,一是存在碳化物分布不均匀、尺寸大小存在差异等问题;二是退火工艺固定化、格式化等问题,未能适应轴承钢的发展;三是球化退火后的组织检验粗糙化、不够细致。球化工艺的发展趋势,一是要在轧钢或锻压生产阶段通过引入塑性变形或增大冷却过冷度等方法来保证片层组织更加均匀、细化,无网状渗碳体;二是要开发新的球化工艺,例如在有可能的条件内引入电场、磁场以及高温高压应力场等方法来改善球化工艺;三是要将球化组织的定量化检验标准化。     

膨胀珍珠岩敏化的乳化炸药爆速试验研究

文章分析了乳化炸药的膨胀珍珠岩敏化机理，通过对爆速测试，主要研究膨胀珍珠岩敏化的乳化炸药的密度，膨胀珍珠岩含量，复合敏化剂等因素对乳化炸药爆速的影响，并对构成复合酶化剂的各组分对乳化炸药焊速的影响程度进行了显著性分析。     

Steelmaking in India – new evidence from microscopic and archaeometallurgical analysis from middle Ganga plain,Balirajgarh

The present study deliberates on the archaeometallurgical examination of 2300 years old excavated iron nail from India's middle Ganga plain of Balirajgarh. The nail was subjected to multianalytical investigations in order to determine the raw materials used, manufacturing technology and preservation state. The combined analytical techniques optical microscopy, scanning electron microscopy-energy dispersive X-ray spectrometry (SEM-EDX), Vickers hardness and X-ray diffractometry shed light towards the characterisation and use of the iron artefact. Special attention was paid for qualitative and quantitative analysis of slag inclusions, metal matrix and corrosion products. The presence of heterogeneous microstructure and inclusion of impurities suggests that nail has been produced through the direct process and work hardened. The noncorroded nail is made of hypereutectoid steel and used for building purpose. The study is important to understand the role of technology in the evolution of cultural changes in India that also provides archaeometric data on the method used in the forging work.     

New pearlitic steels for 21st century rail applications

To improve competitiveness,the nation’s railroads have increased the axle loads and speed of the trains.This has led to a rapid decrease in the life expectancy of premium rails through accelerated wear,rolling contact fatigue and fracture.To counter this effect,the railroads need rails that exhibit better performance in these areas.A research program has been initiated to study the microstructural aspects of near-eutectoid steels that would improve these properties.The first phase of the work was to carefully characterize the existing commercial rail steels in terms of pearlite interlamellar spacing,steel cleanliness and the presence of pro-eutectoid cementite on prior-austenite boundaries.These characterizations were then correlated with both mechanical properties and overall rail performance.The second phase of the program was to develop a better microstructure through control of composition,thermomechanical processing and cooling path.This was achieved through the use of laboratory-melted heats of experimental near-eutectoid compositions and a computer controlled MTS compression machine modified for axisymmetric compression testing and subsequent controlled cooling.The optimum processing route for these new steels has been determined,and pilot-scale heats have been melted,hot rolled and cooled using the information gained from the MTS investigations.The mechanical properties of these new steels have been determined and the rail performance tests are being conducted using laboratory-scale evaluation.Ultimately,these new rail steels will be tested under commercial conditions on the TTCI test track in Pueblo,Colorado.This paper will report on the alloy and processing design and resulting properties of the steels developed in this research program.Guidelines for future rail compositions and processing to obtain improved properties and performance will be presented.     

热扩散法电镀黄铜珠光体钢丝湿式拉拔断丝研究

为找出电镀黄铜钢丝湿拉发生颈缩断丝的原因,通过扫描电镜、能谱仪以及X射线衍射仪分析了湿式拉拔正常和异常的钢丝的微观组织和镀层物相,并用拉伸试验机检测了其力学性能。结果发现,2种镀黄铜钢丝的微观组织均为伪共析珠光体,未发现异常的先共析铁素体和球化渗碳体,二者力学性能也无明显差异。湿拉异常的镀黄铜钢丝的镀层中,β-黄铜相的质量分数高达24%,是湿拉正常钢丝的6倍。当镀黄铜钢丝的微观组织和力学性能良好时,镀层中过多的硬脆β-黄铜相是导致湿拉出现颈缩状断口的重要原因。通过在规定温度下对异常钢丝镀层重新做热扩散处理,可使湿拉断丝率从5.0次/t下降至0.1次/t。     

The effects of alloying elements on tensile strength and the occurrence of delamination in cold-drawn hyper-eutectoid steel wires

The effects of alloying elements and initial interlamellar spacing on tensile strength and the occurrence of delamination in cold-drawn hyper-eutectoid steel wires were investigated under equivalent drawing conditions. The initial interlamellar spacing showed little influence on the occurrence of delamination. The addition of Cr effectively increased attainable tensile strength, since the added Cr not only increased tensile strength but also delayed delamination. The addition of Ni also increased attainable tensile strength, since the effect of the added Ni on delaying delamination prevailed over the tendency to decrease tensile strength and work hardening. The addition of Cr increased the attainable tensile strength more effectively than the addition of Ni in cold-drawn hyper-eutectoid steel wires, although the added Ni markedly delayed delamination-associated strain.     

Modeling of Austenite Decomposition in Low SiMn TRIP Steel During Cooling

Transformation behavior in low carbon SiMn TRIP steel was investigated by means of microstructural observation and computer modelling. A transformation model in which transformation is controlled by carbon diffusion was suggested, which well described the volume fractional change of ferrite, pearlite, and bainite during continuous cooling. The influence of Si content and austenite grain size was thoroughly investigated. The calculated results indicated that Si retards pearlite transformation, accelerates polygonal ferrite transformation, refines the austenite grain, and increases the ferrite transformation rate.