On the linear correlation between microhardness and mechanical properties in polar polymers and blends

The tensile elastic modulus (E), yield stress (σ_Y) and microhardness (MH) of neat and binary and ternary blends of glassy semicrystalline ethylene–vinyl alcohol copolymer (EVOH), a glassy amorphous polyamide and a semicrystalline nylon‐containing ionomer covering a broad range of properties were examined. The tests were carried out on dry and water‐equilibrated samples to produce stiffer and softer materials, respectively. From the results, more accurate linear correlations were found to describe adequately the microhardness, modulus and yield stress of these strongly self‐associated polymers through hydrogen bonding. Copyright © 2003 Society of Chemical Industry     

激光熔敷合金层组织及腐蚀磨损特性研究

利用ＣＯ＿２连续激光器在４５钢表面进行了激光熔敷镍基合金、镍基Ｃｒ＿２Ｏ＿３合金和镍基ＷＣ合金，以２Ｃｒ１３不锈钢为对比材料，系统地研究了激光熔敷层在不同冲击速度和腐蚀介质浓度下的腐蚀磨损特性，并根据组织分析、显微硬度测试及腐蚀磨损后的表面形貌观察，探讨了激光熔敷层的腐蚀磨损过程。结果表明：激光熔敷层的腐蚀磨损性能均比２Ｃｒ１３不锈钢好。     

Evaluation of the reactivity of titanium with mould materials during casting

A methodology for evaluating the reactivity of titanium with mould materials during casting has been developed. Microhardness profiles and analysis of oxygen contamination have provided an index for evaluation of the reactivity of titanium. Microhardness profile delineates two distinct regions, one of which is characterised by a low value of hardness which is invariant with distance. The reaction products are uniformly distributed in the metal in this region. The second is characterised by a sharp decrease in microhardness with distance from the metal-mould interface. It represents a diffusion zone for solutes that dissolve into titanium from the mould. The qualitative profiles for contaminants determined by scanning electron probe microanalyser and secondary ion mass spectroscopy in the as-cast titanium were found to be similar to that of microhardness, implying that microhardness can be considered as an index of the contamination resulting from metal-mould reaction.     

Studies on thermal fatigue in 3Cr2W8V die steel by positron lifetime and hardness measurements

Studies on thermal fatigue in 3Cr2W8V die steel have been carried out by using positron lifetime and microhardness measurements. It is found that the mean positron lifetime and the microhardness exhibit periodic up-and-down variations with an increase in the number of fatigue cycles. The experiments indicate that in the process of thermal fatigue there are two opposing effects on variation of defects: microdeformation and dynamic recovery and recrystallization.     

On the microhardness testing of electrically stressed poly(phenylene oxide): Polystyrene blends

Microhardness measurements have been performed on untreated (virgin) and electrically stressed, solvent‐cast laboratory‐prepared samples of pure poly(phenylene oxide) (PPO), pure polystyrene (PS), and PPO : PS polyblends with different weight proportions. Results of such measurement on untreated polyblend sample show that microhardness (H_v) increases with increase in the content of PS up to 10 wt %, which attributed to the existence of homogeneous phase morphology. However, this feature is not observable in samples containing higher content of PS. Electrical stress is found to modify considerably the mechanical property of polymer. The effect of electric field on the microhardness of such samples (PPO : PS :: 90 : 10) has been characterized by the existence of a peak. Trapping of charge carriers in electrically stressed samples imparts hardening to the polyblend up to an applied step field of 190 kV/cm. However, the excessive charging beyond this step field value destroys this characteristic. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

超声辅助激光修复镍基高温合金V形槽

为了提高失效零件的修复质量,以V形槽为修复对象开展研究,在修复过程中引入超声振动. 耦合声场、温度场与流场建立超声辅助激光修复V形槽的非线性瞬态模型,对修复过程熔池形貌及其温度场进行数值模拟,并开展相关实验研究,分析超声对修复区组织及性能的影响机制. 数值模拟结果表明,超声振动能加速熔池流动与散热,提高熔深,细化晶粒并改善V形槽底部难熔区域的修复效果. 金相、扫描电子显微镜和电子背散射衍射分析结果表明,在超声作用下,晶粒尺寸和一次枝晶间距得到细化,Laves相更加弥散,Nb元素的富集受到抑制;常温和高温硬度在超声作用下分别提高了11.1%、10.4%. 研究表明,超声振动能有效改善镍基高温合金V形槽激光修复区的微观形貌,提高力学性能.     

用GA-BP算法研究超音速电弧喷涂JCW-S-AM涂层显微硬度与工艺参数间的关系

采用超音速电弧喷涂设备在不同工艺参数条件下制备JCW-S-AM涂层,利用显微硬度计测定各种涂层的显微硬度.根据测试结果,运用GA-BP算法构建涂层显微硬度与喷涂电压、喷涂电流的关系模型并进行工艺参数优化.研究结果表明:喷涂电压和喷涂电流对涂层显微硬度均有影响,呈现非线性规律,并且电压和电流之间存在交互作用;通过遗传算法优化,获得的最佳喷涂工艺参数为:喷涂电压29V,电流200A.此时JCW-S-AM涂层显微硬度最大.     

The internal-nitriding behavior of 310 stainless steel with and without Al and Ti additions

The internal-nitriding behavior in ammonia-hydrogen atmospheres of type-310 stainless steel and 310 to which either 2 wt.% Ti or 3 wt.% Al were added was studied over the range of 550–950°C. An Fe-24Cr binary alloy was included to assess the role of a BCC crystal structure vs the FCC crystal structure of 310 stainless steel. The BCC alloy exhibited the most rapid kinetics as expected. X-ray diffraction showed only the presence of CrN in all the alloys up to 735°C. At 850°C and above, both CrN and Cr₂N were detected. The nonformation of TiN and AlN at lower temperatures is attributed to nucleation problems. Precipitates were extremely fine (unresolvable even at 20,000×) at 563°C and became much coarser with increasing temperature. The precipitate density, size, and shape varied across the internal-nitriding zone at the higher temperatures. External scaling was noted at 850°C and above, however, it was not a continuous film. The activation energy of internal nitriding from 563–735°C ranged from 3.8 kcal/mol for 310+2Ti to 18.2 kcal/mol for 310+3Al; from 850–950°C, the activation energy ranged from 44 (310+2Ti) to 56.6 kcal/mol (310+3Al). Microhardness profiles show that an intermediate zone exists between the nitride case and the base metal. The origin of this zone is discussed.     

Cu-Ni-Si合金的时效强化机制分析

分析了Cu-3．2Ni-0．75Si-0．30Zn合金在时效过程中显微硬度的变化规律。结果表明，合金在500℃时效时可以获得最大显微硬度，而550℃时效时可以获得最高导电率。分析表明，该合金的强化效果主要取决于析出第二相体积分数以及第二相颗粒半径；第二相体积分数接近平衡态以前，第二相的析出对强化效果起主要作用；而体积分数接近平衡态以后，第二相颗粒的长大则成为导致强化效果降低的主要因素。