Grain boundary structure and the effect of boron in Ni3Al

A model is developed to explain the experimental observation that small additions of boron to Ni₃Al reduce the effectiveness with which grain boundaries strenghthen the alloy, following the proposal of Schulson et al. [Acta metall.34, 1395 (1986); Scripta metall.19, 1497 (1985)]. This model is based on the effect of ordering on the mobility of grain boundary dislocations. If the addition of boron lowers the difference in energy between different ordering configurations at the boundary, then it should promote accommodation of stress concentrations by the motion of grain boundary dislocations.     

硼泥中硼的形态分析

硼与变色酸可形成强荧光络合物,采用分子荧光法对硼泥中硼的总量进行测定。在此基础上,选用不同的溶剂,通过连续浸取方法对硼泥中硼的分布及形态进行分析。结果表明:在λex\λem=313/380 nm,硼量在10~250 ng/25 mL范围内呈良好线性关系。硼泥中总硼含量为4.01 g/kg;各形态硼含量(w/%)依次为:水溶态(49.13)>醋酸溶解态(16.46)>螯合态(14.96)>盐溶态(3.34)>盐酸羟胺溶解态(1.00)>残渣态(0.50),测定结果对硼泥的综合治理及资源再生有一定指导意义。     

Temperature effect on bending strength of hot-pressed boron carbide materials

The paper examines three groups of samples based on B₄C and B₁₃C₂ powders (with additions of Al and Al₂O₃ in the amount of 2 and 5 wt.%, respectively). It is established that the maximal strength (445 MPa) is characteristic of the material B₁₃C₂ over the whole temperature range. It does not change up to 1600°C. The increase in strength of B₄C-based samples is revealed over the range of 1200 to 1600°C, mainly for high-porous materials (10–12%). Presumably, this is due to the higher relaxation properties of porous material microstructure. __________ Translated from Poroshkovaya Metallurgiya, Vol. 46, No. 5–6 (455), pp. 60–68, 2007.     

Studies on the effect of processing parameters on electroless coating of copper on boron carbide particles

Boron carbide a hard refractory semiconductor ceramic material due to its unique structural properties and high neutron cross section finds application as structural materials and neutron shielding material. Its applicability is reduced due to low sinterbility and dispersiblity which can be overcome by copper coating. The effect of Electroless coating parameters on the surface deposits is characterised. The studies revealed that uniform and smooth coating was observed for pH11 at bath temperature of 348K. The prolonged suspension of B₄C particles on the reaction bath has little effect on coating but it inturns reduces the adhesion of coating on activated particles.     

The boron hardenability effect in thermomechanically processed,direct-quenched 0.2 Pct C steels

The segregation and precipitation of boron have been studied in thermomechanically processed 0.2C-0.6Mn-0.5Mo steels containing nominally 0, 10, 20, 50, and 100 ppm B. These steels were hot-rolled in the laboratory (in simulation of production multipass rolling), and their transformation behavior during subsequent water quenching was examined for different finish-rolling temperatures (980 °C and 870 °C) and quenching temperatures (730 °C to 950 °C). The results showed that in general, a “free” boron content of 10 to 20 ppm (which is similar to the levels used for conventional quenched-and-tempered steels) will provide a boron hardenability increment similar to that for conventional quenched-and-tempered steels. The delay time prior to quenching (over the range of 10 to 100 seconds) did not have a significant effect on hardenability except in the steels containing 50 or more ppm B. In these higher B steels, precipitation of borocarbides occurred along austenite grain boundaries with a resultant decrease in hardenability.     

硼对低碳铝镇静钢中AlN、MnS析出的影响

通过实验室模拟薄板坯连铸连轧(TSCR)流程实验,研究了向低碳铝镇静钢中加入质量分数为3.0×10-3%的微合金元素B对AlN、MnS在连铸连轧过程中析出的影响.结果表明:微合金元素B可以在高温奥氏体中优先与自由N结合形成粗大BN颗粒,且常与MnS复合析出,抑制了细小AlN的析出,减少了钢中细小AlN的含量.     

硼对低碳铝镇静钢中AIN、MnS析出的影响

通过实验室模拟薄板坯连铸连轧(TSCR)流程实验,研究了向低碳铝镇静钢中加入质量分数为3.0×10-3%的微合金元素B对A lN、MnS在连铸连轧过程中析出的影响.结果表明:微合金元素B可以在高温奥氏体中优先与自由N结合形成粗大BN颗粒,且常与MnS复合析出,抑制了细小A lN的析出,减少了钢中细小A lN的含量.     

含硼生铁冶炼硼钢新工艺及其硼钢性能研究

含硼生铁是高炉火法分离硼铁矿提取硼时(富硼渣,w(B_2O_3)≥12%)产生的另一种重要产品.研究了以此为原料直接冶炼硼钢的新工艺及硼钢试样的力学性能,结果表明:采用预脱硫、脱硅处理得到含硼半钢再冶炼硼钢的新工艺,其S、P等杂质含量均能满足硼钢标准要求,而最关键的B含量(质量分数)也可控制在0.0005%～0.0035%,即硼钢要求的标准范围;其硼钢试样材料的拉伸、冲击韧性等力学性能指标优于20Mn2、15MnVB,而与40MnB、45MnB结构合金硼钢相当;通过冶炼后期控制其它合金化成分,能达到国标GB/T 3077-1999中相近成分的硼钢性能.     

The effect of thermal cycling on the mechanical properties of various aluminum alloys reinforced with unidirectional boron fibers

The mechanical properties of boron reinforced 6061, 1100, or 2024 aluminum alloys were measured at room temperature in the as-received condition and after thermal cycling. It was observed that cycling these materials through temperatures that varied between room temperature and either 588 K, 638 K, or 698 K could seriously degrade the properties. Observations of the surfaces of some specimens indicated that small perturbations appeared after very few cycles. These widened and deepened as the test proceeded until they developed into macroscopically visible surface cracks. The appearance of these cracks coincided with the maximum degradation of the mechanical properties. The extent of the observed effects depended on alloy type and the maximum cyclic temperature used. Increasing the maximum temperature produced an increase in the damage. The properties of the reinforced 2024 material were the most affected. A smaller degradation was produced in the properties of the 6061 material; however, some of the properties of the reinforced 1100 material were improved slightly.     

The role of boron in the grain

It has been known for nearly forty years that the presence of boron in Al-Ti grain refiners has a beneficial effect. Three major theories have been proposed to explain the phenomenon: 1. Boron alters important phase relationships in the Al-Ti-B system. 2. Boron forms TiB₂, which is nearly insoluble and acts as an effective nucleus for grain refining. 3. A metastable phase, (Al, Ti)B₂, forms and either acts directly as a grain refining agent, or somehow alters the phase relationships as in (1) above. A close examination of these theories, however, shows that none is wholly satisfactory in explaining the experimental evidence. Hence, experimental work was carried out to elucidate further the important role of boron. The (Al, Ti)B₂ phase was found to be an effective nucleant in some alloys, in agreement with prior work. In addition, this study suggests that boron may at times improve the grain refining response of Al-Ti alloys by altering the surface structure of TiAl₃ nuclei. The mechanisms of grain refinement, therefore, appear to be more complex than has generally been realized. Formerly Research Engineer, Cabot R & D Laboratories, Reading, PA Formerly Senior Research Engineer, KB Alloys, Reading, PA     

Nature of boron carbonitride I. Conditions of preparation of boron carbonitride

Conclusions A study was made of the preparation of boron carbonitride by various techniques. It is shown that the method of synthesis from simple substances, involving nitriding boron and carbon black in a nitrogen atmosphere at temperatures of 1800–2000°C, yields a product corresponding, according to chemical analysis, to the composition BNC. Standard powder metallurgy techniques appear to be unsuitable for the production of massive boron carbonitride specimens.Translated from Poroshkovaya Metallurgiya, No. 1 (97), pp. 27–33, January, 1971.