热压烧结Ti3AlC2材料的制备、结构与性能研究

采用热压工艺研究了不同工艺制度和原料中不同的Si含量对Ti3AlC2合成的影响.研究表明在1 300℃～1 500℃,30MPa压力和Ar气氛中热压摩尔比为n(TiC)n(Ti)n(Al)n(Si)=2110.2的混合粉末,可以得到纯度达98%(质量分数)以上的致密块体Ti3AlC2材料;添加的Si均匀分布在基体中,形成固溶体,当添加Si的摩尔比为0.2时,固溶体的化学式为Ti2 76Al0 78Si0.22C2.烧结试样的晶体为层片状结构,1 300℃和1 400℃时,烧结试样的晶粒尺寸分别为10μm～15μm和20μm～30μm.材料的维氏硬度为3.3 GPa～5.0 GPa,弹性模量为289 GPa,抗压强度为785 MPa,抗弯强度为375 MPa,断裂韧性为7.0 MPa·m1/2;25℃时,电导率为3.1×106 S·m-1,热容为125.4 J/mol·K,热导率为27.5 W/m·K;热膨胀系数为8.8×10-6 K-1.     

Molybdate and tungstate as corrosion inhibitors for cold rolling steel in hydrochloric acid solution

The inhibition effects of molybdate and tungstate on the corrosion of cold rolling steel (CRS) in hydrochloric acid solution (0.1-0.5 M) were investigated by weight loss and electrochemistry methods. The results reveal that both molybdate and tungstate are very good inhibitors with little concentration. The adsorption of inhibitors on the CRS surface basically obeys the Langmuir adsorption isotherm equation. The effect of temperature on the corrosion behavior of CRS was also studied at 25 °C and 35 °C, the thermodynamic parameters such as adsorption heat (ΔH⁰) and adsorption free energy (ΔG⁰) were calculated. In the same conditions, a comparative study of corrosion inhibition of molybdate and tungstate indicated that molybdate was the better inhibitor in 0.1 M HCl. However, the value of percentage inhibition efficiency (IE) was dependent on the concentration of inhibitors in 0.2-0.5 M HCl. It seemed that molybdate did not have the strong inhibitive effect compared to tungstate with relatively small concentration of inhibitors, but molybdate was a better inhibitor over a wide concentration range of inhibitors. A kinetic study of cold rolling steel in uninhibited and inhibited acid was also discussed. Various parameters such as rate constant k and the kinetic parameter B were calculated for the reactions of corrosion. Polarization curves showed that both molybdate and tungstate are mixed-type inhibitors in acidic media.     

我国铸造有色合金及其特种铸造技术发展现状

结合我国在铸造有色合金领域的发展概况,从合金发展、应用和有色合金熔体技术以及特种铸造在有色合金中的应用角度,分析了五十年来我国在该领域所取得的成绩和存在的问题,以引起广大科技工作者和生产技术人员对这方面自主创新的重视,不断提高铸造有色合金的技术水平,扩大其应用领域。     

钽钛合金再结晶退火工艺研究

研究了二元钽钛合金丝经拉拔加工中间再结晶退火处理后的组织。结果发现:变形量为12%的!1.5mm的钛钽合金丝经1000℃×1h退火能够发生完全再结晶;变形量由17%增大至70%,再结晶温度下降约40℃,变形量对再结晶温度影响较大;变形量越大,再结晶后的组织晶粒细小。     

脲醛呋喃树脂中氮含量的测定

脲醛呋喃树脂中的含氮量,一般采用克氏定氮法,方法繁琐,费时较长,不利于快速分析的要求,本文利用气相色谱法对脲醛呋喃树脂中的氮含量进行分析测定,并建立了测定方法.方法简捷、快速、重现性好,加标回收率在100.8～109.0之间,准确度较高,可很好的满足工业生产中快速分析的要求.     

碳化物在高铬铸铁高应力磨料磨损中的影响

对不同载荷作用下的高铬铸铁在耐磨实验机上进行了磨料磨损试验;对在不同的碳化物对基体的保护作用与碳化物的剥离进行了相关的分析.结果表明载荷在一定值以下磨损较为缓慢,当载荷超过一定值时,磨损急剧加剧,随着载荷的增加"尺寸较小"的碳化物首先剥离基体,当载荷继续增大时,"尺寸较大"的碳化物也剥离基体并有碎裂现象.这要求高铬铸铁中的碳化物不仅要分布均匀,碳化物的尺寸也要合适.     

用扩冲法修复凹形护环的新工艺

详细介绍了用扩冲法对液压胀形出现凹形的护环进行修复的方法。实践证明,扩冲法修复护环简单、经济、实用。     

喷射成形高温合金沉积态组织的形成与演变

对喷射成形高温合金的组织形成及其从雾化过程的树枝晶向等轴晶组织的演变过程进行了分析，结果表明，半液态层中发生的枝晶破碎，重熔所造成的核心增殖作用为等轴晶组织的形成提供了大量结晶核心，在此基础上枝晶臂的合并，粗化以及未严重固相枝晶的粗化和均匀化产生了喷射成形材料所持有的非枝非等轴晶组织。     

面向特征的STEP-NC加工方法研究

介绍了STEP-NC数据结构的基本特征，分析了STEP-NC控制器的功能结构，研究了从STEP-NC文件中直接提取制造信息并在实验平台上进行实际加工的基本方法，建立了基于特征的数控加工系统，提出了相应的实现方法和技术。最后在VC＋＋6．0和ST-Developer10集成环境下，利用开放式三维实验平台提供的运动控制器函数库和动态连接库，开发了一个基本的STEP-NC控制平台，其基本功能包括STEP-NC文件的翻译、制造信息的提取、执行和控制等，并能以特征为单位进行加工实验。     

Activation of hydrogen storage materials in the Li–Mg–N–H system: Effect on storage properties

We investigate the thermodynamics, kinetics, and capacity of the hydrogen storage reaction: Li₂Mg(NH)₂ + 2H₂  Mg(NH₂)₂ + 2LiH. Starting with LiNH₂ and MgH₂, two distinct procedures have been previously proposed for activating samples to induce the reversible storage reaction. We clarify here the impact of these two activation procedures on the resulting capacity for the Li–Mg–N–H reaction. Additionally, we measure the temperature-dependent kinetic absorption data for this hydrogen storage system. Finally, our experiments confirm the previously reported formation enthalpy (ΔH), hydrogen capacity, and pressure–composition–isotherm (PCI) data, and suggest that this system represents a kinetically (but not thermodynamically) limited system for vehicular on-board storage applications.