2004 IEEE International Solid-State Circuits Conference (IEEE Cat. No.04CH37519)
A 17 GHz RF receiver consisting of an LNA and doubly-balanced mixers coupled by a monolithic 3.7:... more A 17 GHz RF receiver consisting of an LNA and doubly-balanced mixers coupled by a monolithic 3.7:1 step-down transformer realizes over 70 dB of image-rejection in a 100 GHz-f/sub T/ SiGe BiCMOS technology. Quadrature LO signals are generated with electronically tunable phase from a subharmonically injection-locked oscillator. The measured IIP3 is -5.1 dBm with 17.3 dB conversion gain and 6.5 dB NF (SSB, 50 /spl Omega/) at 17.2 GHz. The 1.9/spl times/1.0 mm/sup 2/ IC consumes 62.5 mW from a 2.2 V supply.
The recrystallization behavior of three Nb-bearing high-strength low-alloy (HSLA) steels was inve... more The recrystallization behavior of three Nb-bearing high-strength low-alloy (HSLA) steels was investigated during multipass deformation under continuous cooling conditions. The niobium concentrations of these steels varied from 0.05 to 0.09 wt pct. The specimens were tested on a computerized torsion machine using a simulation schedule of 17 passes. Deformation temperatures of 1180 ~ to 700 ~ were employed, together with pass strains of 0.1 to 0.7, strain rates of 0.2 to 10 s-j, and interpass times of 5 to 200 seconds. By means of mean flow stress vs 1000/T diagrams, the effect of the deformation conditions on the no-recrystallization temperature (T,r), the temperature at which recrystallization is no longer complete, was determined. It decreases with increasing strain and also decreases slightly with increasing strain rate. There is a T,r minimum at times of about 12-15 seconds, and both increases and decreases from this value raise this characteristic temperature. When the interpass times are short, solute atoms control the rate of recrystallization, the extent of which decreases as the time is decreased. When the interpass times are long, precipitation takes place and retards recrystallization, so that the extent of softening decreases.
One of the requirements to successfully produce high-strength pipeline steel is the optimization ... more One of the requirements to successfully produce high-strength pipeline steel is the optimization of precipitation strengthening. Some high-strength pipeline grades rely on increased levels of niobium (Nb); in these grades, it is important to ensure that all of the Nb is effectively employed. It is generally accepted that the choice of coiling temperature (i.e., the temperature of steel strip just before coiling) is critical in maximizing Nb carbonitrides in ferrite. Additional control of this precipitation may be attained by deformation at these coiling temperatures, an approach termed "cool deformation." In this work, steel specimens were heated to a temperature of 1200 °C and held for 20 minutes to ensure significant dissolution of the Nb precipitates. Some specimens were aged at 400 °C for times ranging from 10 minutes to 10 hours followed by air cooling. Others were subjected to deformation at 400 °C (cool deformation) prior to aging. It was found that cool deformation improves the mechanical properties (both yield and tensile strengths are significantly higher than those of the aged only specimens). A field emission gun-scanning electron microscope (FE-SEM) was applied successfully in the characterization of Nb precipitates using carbon extraction replicas. The FE-SEM observation of the replicas confirmed the presence of Nb precipitates in ferrite. The FE-SEM could analyze small particles (below 50 nm) embedded in the steel, but the analysis had to be carried out at low voltages to maximize spatial resolution, resulting in a poor signal. However, it is possible to analyze carbon extraction replicas in the FE-SEM using high voltages, because the interaction volume effect is no longer a problem.
The relationship between mechanical properties and microstructural characteristics of pearlite wa... more The relationship between mechanical properties and microstructural characteristics of pearlite was investigated using various heat treatments on a hypereutectoid steel. The materials were reheated between 900 and 1200 • C and these microstructures were then subjected to isothermal transformation at temperatures of 550, 580 and 620 • C. For the hypereutectoid steel, the mean value of the interlamellar spacing was observed to increase with increasing reheat and transformation temperatures. Examination of the mechanical properties of the resulting pearlitic microstructures indicated that the strength was related primarily to the interlamellar spacing by a Hall-Petch type relationship, while the ductility was dependent also on the prior-austenite grain size and pearlite colony size.
The transformation behaviours and microstructural characteristics of three B-containing steels we... more The transformation behaviours and microstructural characteristics of three B-containing steels were investigated. [n particu lar, the effects of deformation in the no-recrystallization temperature range and cool ing rate were studied by means of compression tests. It was found that over a large cooling rate range (from 1 to 50'Cls). Mo-Nb-B steel exhibits microstructures consisting of a mixture of plate-like or lath-like ferrite with retained austenite or martensite (i.e. M/A) islands. This is basically a low carbon bainitic microstructure. and can be identified as B, in the Bramfitt and Speer classification system. The lengths of the ferrite laths increase and the widths decrease as the cooling rate is increased. The shapes and distributions of the M/A islands change from being blocky and randomly distributed to fine and more aligned, as the cooling rate is increased. Also, the lengths of the bainitic ferrite laths are shortened by heavy deformation in the norecrystallization temperature range. The microstructures of the Nb-1 5B and B-only steels are basically polygonal ferrite at low coo]ing rates, however, the fractions of bainite in these two grades increase with cooling rate. The minimum cooling rate required for avoiding polygonal ferrite formation during continuous cooling are much higher in these two grades than in the Mo-Nb-B steel.
A 17-GHz RF receiver, consisting of a low-noise amplifier (LNA) and doubly balanced mixers couple... more A 17-GHz RF receiver, consisting of a low-noise amplifier (LNA) and doubly balanced mixers coupled by a monolithic 3.7:1 step-down transformer, realizes over 75 dB of image rejection in a production 100-GHz SiGe BiCMOS technology. A new coupling transformer winding improves the magnetic coupling coefficient by more than 20% compared to conventional designs, which reduces parasitic effects and increases the overall efficiency of the LNA/mixer combination. Quadrature LO signals with electronically tunable phase are generated by a subharmonically injection-locked oscillator. The measured receiver IIP3 is 5.1 dBm with 17.3-dB conversion gain and 6.5-dB noise figure (SSB 50) at 17.2 GHz. The 1 9 1 0 mm 2 IC consumes 62.5 mW from a 2.2-V supply.
The occurrence of dynamic recrystallization in hypoeutectoid and hypereutectoid steels of 0.7 and... more The occurrence of dynamic recrystallization in hypoeutectoid and hypereutectoid steels of 0.7 and 0.9% carbon was investigated under isothermal conditions. Compression tests were performed using single deformation schedules at temperatures between 900 and 1050 °C and strain rates of 0.01s-1 , 0.1s-1 and 1s-1. It was observed that the activation energy for deformation decreased with increasing carbon content in the steels. The peak and steady state strain values determined from the flow curves generated by hot compression deformation were used to examine the possible evolution of grain size by recrystallization. Résumé-La recristallisation dynamique d'aciers hypoeutectoïdes et hypereutectoïdes à 0.7 et 0.9 % de carbone est étudiée. Des tests de compression sont effectués dans des conditions isothermes à des températures comprises entre 900 et 1050 o C et à des vitesses de déformation de 0.01 s-1 , 0.1 s-1 et 1s-1. Il est observé que l'énergie d'activation de déformation diminue lorsque le taux que carbone dans l'acier augmente. Les valeurs de la déformation à la contrainte maximale et au début de l'état stationnaire, déterminées à partir des courbes d'écoulement générées par la déformation à chaud, sont utilisées pour étudier l'évolution possible de la taille des grains par recristallisation.
In common magnesium alloys, recrystallization is usually not accompanied with a noticeable change... more In common magnesium alloys, recrystallization is usually not accompanied with a noticeable change of deformation texture resulting in, strong mechanical anisotropy. The aim of this work is to investigate the effect of dynamic or strain induced precipitates on texture evolution during hot deformation of Mg-Al-Sn alloys. Mg-Al-Sn alloys have been designed using thermodynamic modeling software, FactSage, based on forming precipitates at hot deformation temperatures. Two alloys have been chosen in a way that one forms precipitates during the hot deformation process, another does not at a certain temperature. Uniaxial compression has been introduced at different strain rates at this elevated temperature to simulate the hot deformation behaviour. Two alloys have been compared in terms of the intensity of basal texture. It was found that the formation of dynamic precipitates during deformation weakens the texture compared to the case where no precipitates were formed.
2004 IEEE International Solid-State Circuits Conference (IEEE Cat. No.04CH37519)
A 17 GHz RF receiver consisting of an LNA and doubly-balanced mixers coupled by a monolithic 3.7:... more A 17 GHz RF receiver consisting of an LNA and doubly-balanced mixers coupled by a monolithic 3.7:1 step-down transformer realizes over 70 dB of image-rejection in a 100 GHz-f/sub T/ SiGe BiCMOS technology. Quadrature LO signals are generated with electronically tunable phase from a subharmonically injection-locked oscillator. The measured IIP3 is -5.1 dBm with 17.3 dB conversion gain and 6.5 dB NF (SSB, 50 /spl Omega/) at 17.2 GHz. The 1.9/spl times/1.0 mm/sup 2/ IC consumes 62.5 mW from a 2.2 V supply.
The recrystallization behavior of three Nb-bearing high-strength low-alloy (HSLA) steels was inve... more The recrystallization behavior of three Nb-bearing high-strength low-alloy (HSLA) steels was investigated during multipass deformation under continuous cooling conditions. The niobium concentrations of these steels varied from 0.05 to 0.09 wt pct. The specimens were tested on a computerized torsion machine using a simulation schedule of 17 passes. Deformation temperatures of 1180 ~ to 700 ~ were employed, together with pass strains of 0.1 to 0.7, strain rates of 0.2 to 10 s-j, and interpass times of 5 to 200 seconds. By means of mean flow stress vs 1000/T diagrams, the effect of the deformation conditions on the no-recrystallization temperature (T,r), the temperature at which recrystallization is no longer complete, was determined. It decreases with increasing strain and also decreases slightly with increasing strain rate. There is a T,r minimum at times of about 12-15 seconds, and both increases and decreases from this value raise this characteristic temperature. When the interpass times are short, solute atoms control the rate of recrystallization, the extent of which decreases as the time is decreased. When the interpass times are long, precipitation takes place and retards recrystallization, so that the extent of softening decreases.
One of the requirements to successfully produce high-strength pipeline steel is the optimization ... more One of the requirements to successfully produce high-strength pipeline steel is the optimization of precipitation strengthening. Some high-strength pipeline grades rely on increased levels of niobium (Nb); in these grades, it is important to ensure that all of the Nb is effectively employed. It is generally accepted that the choice of coiling temperature (i.e., the temperature of steel strip just before coiling) is critical in maximizing Nb carbonitrides in ferrite. Additional control of this precipitation may be attained by deformation at these coiling temperatures, an approach termed "cool deformation." In this work, steel specimens were heated to a temperature of 1200 °C and held for 20 minutes to ensure significant dissolution of the Nb precipitates. Some specimens were aged at 400 °C for times ranging from 10 minutes to 10 hours followed by air cooling. Others were subjected to deformation at 400 °C (cool deformation) prior to aging. It was found that cool deformation improves the mechanical properties (both yield and tensile strengths are significantly higher than those of the aged only specimens). A field emission gun-scanning electron microscope (FE-SEM) was applied successfully in the characterization of Nb precipitates using carbon extraction replicas. The FE-SEM observation of the replicas confirmed the presence of Nb precipitates in ferrite. The FE-SEM could analyze small particles (below 50 nm) embedded in the steel, but the analysis had to be carried out at low voltages to maximize spatial resolution, resulting in a poor signal. However, it is possible to analyze carbon extraction replicas in the FE-SEM using high voltages, because the interaction volume effect is no longer a problem.
The relationship between mechanical properties and microstructural characteristics of pearlite wa... more The relationship between mechanical properties and microstructural characteristics of pearlite was investigated using various heat treatments on a hypereutectoid steel. The materials were reheated between 900 and 1200 • C and these microstructures were then subjected to isothermal transformation at temperatures of 550, 580 and 620 • C. For the hypereutectoid steel, the mean value of the interlamellar spacing was observed to increase with increasing reheat and transformation temperatures. Examination of the mechanical properties of the resulting pearlitic microstructures indicated that the strength was related primarily to the interlamellar spacing by a Hall-Petch type relationship, while the ductility was dependent also on the prior-austenite grain size and pearlite colony size.
The transformation behaviours and microstructural characteristics of three B-containing steels we... more The transformation behaviours and microstructural characteristics of three B-containing steels were investigated. [n particu lar, the effects of deformation in the no-recrystallization temperature range and cool ing rate were studied by means of compression tests. It was found that over a large cooling rate range (from 1 to 50'Cls). Mo-Nb-B steel exhibits microstructures consisting of a mixture of plate-like or lath-like ferrite with retained austenite or martensite (i.e. M/A) islands. This is basically a low carbon bainitic microstructure. and can be identified as B, in the Bramfitt and Speer classification system. The lengths of the ferrite laths increase and the widths decrease as the cooling rate is increased. The shapes and distributions of the M/A islands change from being blocky and randomly distributed to fine and more aligned, as the cooling rate is increased. Also, the lengths of the bainitic ferrite laths are shortened by heavy deformation in the norecrystallization temperature range. The microstructures of the Nb-1 5B and B-only steels are basically polygonal ferrite at low coo]ing rates, however, the fractions of bainite in these two grades increase with cooling rate. The minimum cooling rate required for avoiding polygonal ferrite formation during continuous cooling are much higher in these two grades than in the Mo-Nb-B steel.
A 17-GHz RF receiver, consisting of a low-noise amplifier (LNA) and doubly balanced mixers couple... more A 17-GHz RF receiver, consisting of a low-noise amplifier (LNA) and doubly balanced mixers coupled by a monolithic 3.7:1 step-down transformer, realizes over 75 dB of image rejection in a production 100-GHz SiGe BiCMOS technology. A new coupling transformer winding improves the magnetic coupling coefficient by more than 20% compared to conventional designs, which reduces parasitic effects and increases the overall efficiency of the LNA/mixer combination. Quadrature LO signals with electronically tunable phase are generated by a subharmonically injection-locked oscillator. The measured receiver IIP3 is 5.1 dBm with 17.3-dB conversion gain and 6.5-dB noise figure (SSB 50) at 17.2 GHz. The 1 9 1 0 mm 2 IC consumes 62.5 mW from a 2.2-V supply.
The occurrence of dynamic recrystallization in hypoeutectoid and hypereutectoid steels of 0.7 and... more The occurrence of dynamic recrystallization in hypoeutectoid and hypereutectoid steels of 0.7 and 0.9% carbon was investigated under isothermal conditions. Compression tests were performed using single deformation schedules at temperatures between 900 and 1050 °C and strain rates of 0.01s-1 , 0.1s-1 and 1s-1. It was observed that the activation energy for deformation decreased with increasing carbon content in the steels. The peak and steady state strain values determined from the flow curves generated by hot compression deformation were used to examine the possible evolution of grain size by recrystallization. Résumé-La recristallisation dynamique d'aciers hypoeutectoïdes et hypereutectoïdes à 0.7 et 0.9 % de carbone est étudiée. Des tests de compression sont effectués dans des conditions isothermes à des températures comprises entre 900 et 1050 o C et à des vitesses de déformation de 0.01 s-1 , 0.1 s-1 et 1s-1. Il est observé que l'énergie d'activation de déformation diminue lorsque le taux que carbone dans l'acier augmente. Les valeurs de la déformation à la contrainte maximale et au début de l'état stationnaire, déterminées à partir des courbes d'écoulement générées par la déformation à chaud, sont utilisées pour étudier l'évolution possible de la taille des grains par recristallisation.
In common magnesium alloys, recrystallization is usually not accompanied with a noticeable change... more In common magnesium alloys, recrystallization is usually not accompanied with a noticeable change of deformation texture resulting in, strong mechanical anisotropy. The aim of this work is to investigate the effect of dynamic or strain induced precipitates on texture evolution during hot deformation of Mg-Al-Sn alloys. Mg-Al-Sn alloys have been designed using thermodynamic modeling software, FactSage, based on forming precipitates at hot deformation temperatures. Two alloys have been chosen in a way that one forms precipitates during the hot deformation process, another does not at a certain temperature. Uniaxial compression has been introduced at different strain rates at this elevated temperature to simulate the hot deformation behaviour. Two alloys have been compared in terms of the intensity of basal texture. It was found that the formation of dynamic precipitates during deformation weakens the texture compared to the case where no precipitates were formed.
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