Ivor Jenkins,Cesar Molins,Sr

Abstract

There was perhaps a subtle symbolism in the choice of the 'mile-high city' of Denver, CO, near the foothills of the Rocky Mountains, as the location for this year's MPIF/APMI annual conference on Powder Metallurgy and Particulate Materials. Not only was this the highest elevation at which the North American Conference and Exhibition had been held, but it was far enough away from the source of the difficulties the PM industry is currently facing – the declining fortunes of the Detroit automotive manufacturers – to focus some attention on other issues.     

Slag–graphite wettability and reaction kinetics Part 1 Kinetics and mechanism of molten FeO reduction reaction

Abstract

The present paper reports results relating to the kinetics and mechanism of FeO reduction by graphite, the data being obtained from experimental investigations into the wettability of graphite by molten slag containing FeO. The rate of FeO reduction was determined by measuring the volume of CO gas formed as a result of the reduction of FeO in experiments conducted in the same sessile drop apparatus. The reduction reaction initiated by direct slag–graphite contact produces CO gas which spreads into the molten slag droplet causing foaming of the slag; further reduction of FeO proceeds mostly via indirect reduction. The rate of reduction was found to depend directly on the initial FeO content. An increase in temperature improves the rate of reaction, which has an activation energy of 112·18 kJ mol^-1. These results indicate that transport of FeO (Fe²⁺, O^2- ) in the liquid slag phase is probably the slowest step.     

Size distribution of oxides and toughness of steel weld metals

Abstract

Experiments have been conducted to modify the size distribution of oxide particles in steel weld metals which have predominantly martensitic microstructures. It is found that the toughness improves significantly when the particles are refined, even when the total concentration of oxygen is unchanged in the process.     

稻米中的蛋白质分布与营养分析

综述了稻米蛋白质的分布 ,氨基酸的组成以及二者的相关性 ,并对稻米蛋白质的营养价值进行了分析。蛋白质在稻米中的分布不是均匀的 ,而是表现为由外至内总蛋白质的百分含量逐渐降低。其氨基酸的组成特点为 :疏水性氨基酸 (40 .lmol% ) >酸性氨基酸 (2 6 .0mol% ) >无电荷极性氨基酸 (2 1.8mol% ) >碱性氨基酸 (12 .2mol% )。蛋白质含量同赖氨酸 (Lys)含量呈负相关 ,同酪氨酸 (Tyr)、苯丙氨酸 (Phe)呈正相关。稻米蛋白质是一种优质蛋白质 ,米粒外层蛋白质的营养价值最高 ,中层次之 ,粒心又略有增高。     

Determination of the metal/die interfacial heat transfer coefficient and its application in evaluating the pressure distribution inside the casting during the high pressure die casting process

Abstract

High pressure die casting (HPDC) experiments were conducted on a 650 t cold chamber die casting machine to study the interfacial heat transfer behaviour between casting and die. A 'step shape' casting and two commercial alloys namely ADC12 and AM50 were used during the experiments. Temperature and pressure measurements were made inside the die and at the die surface. The metal/die interfacial heat transfer coefficient (IHTC) was successfully determined based on the measured temperature inside the die by solving the inverse heat transfer problem. The IHTC was then used as the boundary condition to determine the 3-D temperature field inside the casting. Based on the predicted temperature distribution, the pressure distribution inside the casting was evaluated by assuming that the transferred pressure from the plunger tip of the injection side to the casting is primarily influenced by the solid fraction of the casting. Reasonable agreement was found between the determined pressure values and the measured pressures at the die surface of the casting.     

Microstructural characterisation of stir zone containing residual ferrite in friction stir welded 304 austenitic stainless steel

Abstract

Friction stir welding was applied to a 2 mm thick 304 austenitic stainless steel plate. The microstructural evolution and hardness distribution in the weld were investigated. The stir zone (SZ) and thermomechanically affected zone (TMAZ) showed dynamically recrystallised and recovered microstructures, respectively, which are typically observed in friction stir welds in aluminium alloys. The hardness of the SZ was higher than that of the base material and the maximum hardness was observed at the TMAZ. The higher hardness at the TMAZ was attributed to high densities of dislocations and subboundaries. Microstructural observations revealed that the ferrite was formed along grain boundaries of the austenite matrix in the advancing side of the SZ. It is suggested that the frictional heat due to stirring resulted in the phase transformation of austenite to ferrite and that upon rapid cooling the ferrite was retained in the SZ.     

Influence of welding parameters on distribution of wire feeding elements in CO2 laser GMA hybrid welding

Abstract

The effect of welding parameters on the distribution of wire feeding elements has been investigated during CO₂ laser and pulsed gas metal arc hybrid welding process. The molten metal flow on the pool surface and inside of the samples was observed by a high speed video camera and an in situ X-ray transmission imaging system respectively. The results indicate that the fluid flow towards the inside of keyhole, namely inward flow, improves the homogeneity of weld metal. The distribution of alloying elements is more homogeneous in leading laser compared with leading arc, since both of the drag force of the plasma jet and momentum of droplet promote the inward flow in leading laser. Almost homogeneous distribution of alloying elements can be attained if the oxygen content in the shielding gas is more than 2%, since the Marangoni flow direction changes from outward to inward with increasing the oxygen content.     

BODY PRESSURE DISTRIBUTION OF AUTOMOBILE DRIVING HUMAN MACHINE CONTACT INTERFACE

Aiming at the fatigue and comfort issues of human-machine contact interface in automo- bile driving and based on physiological and anatomical principle,the physiological and biochemical process of muscles and nerves in the formation and development of fatigue is analyzed systematically. The fatigue-causing physiological characteristic indexes are mapped to biomechanical indexes like muscle stress-strain,the compression deformation of blood vessels and nerves etc.from the perspec- tive of formation mechanism.The geometrical model of skeleton and parenchyma is established by applying CT-scanned body data and MRI images.The general rule of comfort body pressm'e distribu- tion is acquired through the analysis of anatomical structure of buttocks and femoral region.The comprehensive test platform for sitting comfort of 3D adjustable contact interface is constructed.The test of body pressure distribution of human-machine contact interface and its comparison with subjec- tire evaluation indicates that the biomechanical indexes of automobile driving human-machine con- tact interface and body pressure distribution rule studied can effectively evaluate the fatigue and comfort issues of human-machine contact interface and provide theoretical basis for the optimal de- sign of human-machine contact interface.     

Effect of grain size on grain boundary strengthening of copper bicrystals under cyclic loading

Abstract

To clarify the strengthening effect of grain boundaries (GB), cyclic deformation behaviour of really grown [4¯79] ∥ [1¯25] copper bicrystals with different widths (4, 6, and 8 mm, denoted RB-4, RB-6, and RB-8) of com-ponent crystals and a combined copper bicrystal (denoted CB-6), obtained by sticking component single crystals G1 [4¯79] and G2 [1¯25] together, was investigated. The results showed that the cyclic saturation stresses increased in the order of bicrystals of CB-6 < RB-8 < RB-6 < RB-4. It is indicated that the GB effect caused different degrees of strengthening, which increased with the decreasing width of the RB bicrystals. By surface observation, it was found that only the primary slip system was activated in the combined bicrystal during cyclic deformation. However, an additional slip system appeared near the GB within the crystal G2 [1¯25] in the RB bicrystals (except in the primary slip system), and formed a GB affected zone (GBAZ). The width of the GBAZ was about 400 and 600 μm at plastic strain amplitudes of 0·1% and 0·2% respectively. Meanwhile, using an electron channelling contrast (ECC) technique in the SEM, the dislocation patterns near the GB and within the component crystals were observed. It was found that a two phase structure of persistent slip bands (PSBs) and matrix (or veins) can form in these bicrystals, similar to that in copper single crystals. But these PSBs cannot transfer through the GB during cyclic deformation. Based on the results above, the effect of grain size on GB strengthening of copper bicrystals was discussed.