Characterisation of FR-4 substrate with various plasma treatment conditions

Abstract

The effects of plasma treatment on the surface of the flame resistant-4 (FR-4) substrate with underfills under various treatment conditions (operating gas, operating time, operating power) are investigated by using contact angle measurement, X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). The plasma treatment on substrate surfaces increased the oxygen containing functional groups or the polar component of the surface free energy, improving the wetting characteristics of the underfills/FR-4 substrates. The plasma treatment conditions which minimised the contact angle between the underfills and FR-4 substrates were an operating power of 300 W and operating time of 180 s under Ar gas atmosphere.     

Impact of slag–refractory lining reactions on the formation of inclusions in steel

Abstract

The present study was carried out to investigate the impact of slag– refractory lining reactions on the formation of inclusions during ladle treatment of steel. The experiments were conducted on an industrial scale in the ladle at Uddeholm Tooling AB in Hagfors, Sweden. The inclusion chemistry and population during ladle treatment were studied along with the composition of the ladle glaze, taken from the ladle lining. The inclusions in the steel were classified into four groups according to the Swedish standard SS 111116. SEM/EDS analyses were carried out to identify the phases present in both the inclusions and the ladle glaze. The number of inclusions in the steel before deoxidation was found to increase with the ladle age, i.e. the number of times the ladle had been in use. A similar increase was also found after vacuum degassing and before casting. A great portion of inclusions before casting was found to be supplied by ladle glaze. This observation was further confirmed and explained by thermodynamic analysis. The present results show that ladle glaze is a major source of inclusions in the ladle at Uddeholm Tooling.     

Effects of heat treatment processes on microstructure and properties of 2·25Cr–1Mo–0·25V HSLA steels

Abstract

In the present paper, the effects of the heat treatment processes with two conditioning treatments and four quenching–tempering processes on the mechanical properties of 2·25Cr–1Mo–0·25V high strength low alloyed (HSLA) steel are investigated. The results show that the conditioning treatments have obvious effects on the low temperature impact energy but little effect on the tensile strength. The elevation of the final austenitising temperature increases the strength, whereas it results in the decrease in the low temperature impact energy due to the coarse microstructure. The results of the fracture surfaces analysis further make sure that the fracture surfaces of tensile specimens all exhibit ductile characters with a lot of dimples. However, the fracture surfaces of impact specimens exhibit two typical fracture characters, i.e. the ductile and brittle fracture surface corresponding to the fine and coarse microstructures respectively. In addition, the elongation and reduction in area seem to be insensitive to the heat treatments. Meanwhile, the impact fracture mode is more sensitive to the grain size and not to the low temperature impact energy.     

Development of precipitate size and volume fraction of niobium carbonitrides in stabilised stainless steel

Abstract

Niobium carbonitride (NbX) precipitates have been studied in a niobium stabilised austenitic stainless steel AISI type 347 with approximate nominal composition Fe–0.06C–17.5Cr–11.4Ni–0.8Nb. The steel was extruded to seamless tube, solution annealed at 1100°C for 3 min, water quenched, and subsequently isothermally aged at 700°C for times up to 70 000 h. Size distribution and volume fraction of the coarse distribution (1–10 µm) of NbX particles were measured using scanning electron microscopy (SEM). The fine distribution (～30 nm) was investigated using energy filtered transmission electron microscopy (EFTEM). Size distribution and volume fraction were determined using jump ratio images. Coarse NbX (～0.3% volume fraction) precipitates were formed during solidification and extrusion, and were little affected by solution annealing and isothermal aging. Fine NbX (～0.5% volume fraction) precipitates formed during solution annealing and grew during the first 800 h of aging. Precipitate size determination using EFTEM appears to give accurate results, while volume fraction determination requires homogeneous material for good results.     

A magnetic resonance compatible surgical manipulator: part of a unified support system for the diagnosis and treatment of heart disease

A prototype of a magnetic resonance (MR)-compatible surgical manipulator was designed and evaluated. The manipulator is designed so as to fit into vertical magnetic field open-configuration MR imagers. Moreover, it is designed to work without being fixed to an MR imager, and its electrical circuits and lines of actuators and sensors are independent of the room shield so that it could be installed in various kinds of settings at many MR imager sites without any additional construction. The MR compatibility of the manipulator was evaluated: no noticeable deformation was observed in the MR images even when the manipulator was in motion. Although the signal-to-noise deterioration ratio was higher than that previously reported, the MR images were thought to be good enough for recognizing the whole structure of a targeted organ and for following the relative position of the manipulator tip with regard to the target, i.e. MR tracking.     

Particle break-up during heat treatment of 3000 series aluminium alloys

Abstract

In wrought aluminium alloys, the fragmentation of coarse, iron bearing intermetallic particles by hot rolling is an important development in industrial processing. Here a model 3000 series alloy is used to show that fragmentation can occur prior to hot rolling, during the homogenisation heat treatment. Some fragmented particles display a curved morphology of break-up that results from matrix wetting of two phase (or 'duplex') interfaces in Al₆(Fe,Mn) particles partially transformed to an α-Al–(Fe,Mn)–Si phase. In contrast, samples rapidly heated to temperature in a fluidised bath show an angular break-up indicative of tensile stresses induced by thermal expansion mismatch between the intermetallic particles and aluminium matrix. Although this break-up should not be industrially significant, the transformation induced break-up by wetting may be. More generally, internal boundaries resulting from the transformation to α-Al–(Fe,Mn)–Si phase may be mechanically weak fracture initiation points during hot rolling.     

Influence of Heat Treatment on Damping Behaviour of the Magnesium Wrought Alloy AZ61

The effect of isochronal heat treatments for 1h on variation of damping, hardness and microstructural change of the magnesium wrought alloy AZ61 was investigated. Damping and hardness behaviour could be attributed to the evolution of precipitation process. The influence of precipitation on damping behaviour was explained in the framework of the dislocation string model of Granato and Lücke.     

Development of process for thermomechanical treatment of ultrahigh strength steel prepared by electroslag refining

Abstract

Thermomechanical treatment (TMT) is the simultaneous use of work hardening, and grain refinement along with solid solution and precipitation strengthening. In this investigation, four alloys, with a base composition of 0·28%C, 1·0%Mn, 4·2%Cr, 1·0%Mo, 0·34%V, were prepared by electroslag refining (ESR) and by addition of small amounts of Ti and Nb and by increasing Cr and V to 4·8 and 0·48% respectively. In two of the alloys a yield strength in excess of 1550 MPa was obtained in the as cast quenched and tempered condition. Attempts were made to further increase the yield strength by thermomechanical treatment. The process parameters for thermomechanical treatment were optimised by adopting procedures such as calculation of stability of precipitates, hot compression test, determination of cooling rates in different coolants, and modelling of TTT and CCT diagrams. The process involved prerolling of the ESR ingot to a bar at 1200°C, followed by hot rolling in two passes starting from 950°C and finishing at 850°C with equal deformation of 25% in each pass to convert the bar into plates. These were immediately cooled in one of the cooling media: air, polymer–water solution (1 : 1·5) and oil. Yield strength in excess of 1750 MPa was obtained in oil cooled specimens of the alloy with titanium addition and that where Cr and V were increased. The niobium added specimen gave strengths, similar to that obtained for the base alloy, in spite of the fact that the as cast alloy had shown very high strengths, presumably because of the high soaking temperatures and grain growth. Air cooling gave the lowest strengths and oil cooling the highest.     

Plasticity induced transformation in a metastable β Ti-1023 alloy by controlled heat treatments

Abstract

Investigations into the possibility of improving the strength–ductility relation in a metastable β-titanium alloy (Ti–10V–2Fe–3Al) through plasticity induced transformation (PiTTi) have been carried out. Various heat treatments in the β and/or α+β condition were performed to study their influence on both the microstructure and solute partitioning, which eventually control the PiTTi effect. Stress induced martensite formation promoting such effect has been observed upon compression testing for β and β+(α+β) microstructures. The stress–strain curves exhibiting stress induced martensite show a ～20% increase in strength, while still retaining a reasonable ductility level. Microstructural parameters such as grain size and solute concentration (especially V) in β have been related to the alloy's ability to exhibit PiTTi.     

Effect of Sr on primary α-Fe phase in liquid Al-11.5Si-0.4Mg cast alloy

Abstract

The effect of Sr on the sedimentation of primary α-Fe phase has been investigated at superheating temperatures of 760 and 900 °C. A convection free experimental technique was used to aid in quantifying the primary α-Fe particles sedimented at 600 °C for 4 h. Sr marginally decreases the formed particle weight at normal melting temperature (760 °C), but greatly increases the particle weight at the superheating temperature of 900 °C. Sr refines primary α-Fe particles at both temperatures, causing the increase of the number of primary α-Fe particles, especially when superheated at 900 °C. In addition, Sr causes a decrease in the particle volume fraction but an increase in the number of the sedimented particles, and a great increase in the depth of the sediment in the mould at higher superheating temperatures. These observations are interpreted in terms of the precipitation of Fe rich particles on suspended oxide films, and the rigidisation of suspended films at higher temperatures, possibly as a result of their change in chemistry, but especially as a result of inflation of their doubled-over form by hydrogen, and the effect this has on the multiplication of growing iron rich precipitates as a result of their mechanically unstable substrate.