Effect of joint gap on the quality of laser beam welded near-β Ti-5553 alloy with the addition of Ti–6Al–4V filler wire

Ti–5Al–5V–5Mo–3Cr (Ti-5553) sheets were welded using a Nd: YAG laser system and Ti–6Al–4V filler wire. The effect of joint gap on weld geometry, defects, microstructure, and hardness was investigated. Fully penetrated welds up to a joint gap of 0.5 mm were produced. The two main defects observed were porosity and underfill. The addition of filler wire reduced underfill but increased porosity, especially at large joint gaps. The fusion zone (FZ) microstructure at low joint gaps consisted of retained β with a dendritic morphology. At a joint gap of 0.3 mm, regions of orthorhombic α″ martensite were observed in the weld zone which increased in proportion as the joint gap increased from a volume percentage of 4.9% at 0.3 mm to a volume percentage of 44% at 0.5 mm. Despite the differences in microstructure with increasing joint gap, the FZ hardness remained relatively constant for all joint gaps evaluated.     

Global and Local Mechanical Properties of Autogenously Laser Welded Ti-6Al-4V

Ti-6Al-4V sheets, 3.2-mm in thickness, were butt welded using a continuous wave 4 kW Nd:YAG laser welding system. The effect of two main process parameters, laser power and welding speed, on the joint integrity was characterized in terms of the joint geometry, defects, microstructure, hardness, and tensile properties. In particular, a digital image correlation technique was used to determine the local tensile properties of the welds. It was determined that a wide range of heat inputs can be used to fully penetrate the Ti-6Al-4V butt joints during laser welding. At high laser power levels, however, significant defects such as underfill and porosity, can occur and cause marked degradation in the joint integrity and performance. At low welding speeds, however, significant porosity occurs due to its growth and the potential collapse of instable keyholes. Intermediate to relatively high levels of heat input allow maximization of the joint integrity and performance by limiting the underfill and porosity defects. In considering the effect of the two main defects on the joint integrity, the underfill defect was found to be more damaging to the mechanical performance of the weldment than the porosity. Specifically, it was determined that the maximum tolerable underfill depth for Ti-6Al-4V is approximately 6 pct of the workpiece thickness, which is slightly stricter than the value of 7 pct specified in AWS D17.1 for fusion welding in aerospace applications. Hence, employing optimized laser process parameters allows the underfill depth to be maintained within the tolerable limit (6 pct), which in turn prevents degradation in both the weld strength and ductility. To this end, the ability to maintain weld ductility in Ti-6Al-4V by means of applying a high energy density laser welding process presents a significant advantage over conventional arc welding for the assembly of aerospace components.     

Effect of Postweld Heat Treatment on Microstructure, Hardness, and Tensile Properties of Laser-Welded Ti-6Al-4V

The effects of postweld heat treatment (PWHT) on 3.2-mm- and 5.1-mm-thick Ti-6Al-4V butt joints welded using a continuous wave (CW) 4-kW Nd:YAG laser welding machine were investigated in terms of microstructural transformations, welding defects, and hardness, as well as global and local tensile properties. Two postweld heat treatments, i.e., stress-relief annealing (SRA) and solution heat treatment followed by aging (STA), were performed and the weld qualities were compared with the as-welded condition. A digital image correlation technique was used to determine the global tensile behavior for the transverse welding samples. The local tensile properties including yield strength and maximum strain were determined, for the first time, for the laser-welded Ti-6Al-4V. The mechanical properties, including hardness and the global and local tensile properties, were correlated to the microstructure and defects in the as-welded, SRA, and STA conditions.     

The BIAS map: Behaviors from intergroup affect and stereotypes.

In the present research, consisting of 2 correlational studies (N = 616) including a representative U.S. sample and 2 experiments (N = 350), the authors investigated how stereotypes and emotions shape behavioral tendencies toward groups, offering convergent support for the behaviors from intergroup affect and stereotypes (BIAS) map framework. Warmth stereotypes determine active behavioral tendencies, attenuating active harm (harassing) and eliciting active facilitation (helping). Competence stereotypes determine passive behavioral tendencies, attenuating passive harm (neglecting) and eliciting passive facilitation (associating). Admired groups (warm, competent) elicit both facilitation tendencies; hated groups (cold, incompetent) elicit both harm tendencies. Envied groups (competent, cold) elicit passive facilitation but active harm; pitied groups (warm, incompetent) elicit active facilitation but passive harm. Emotions predict behavioral tendencies more strongly than stereotypes do and usually mediate stereotype-to-behavioral-tendency links. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Dissociation of musical tonality and pitch memory from nonmusical cognitive abilities.

Replicated, validated, and extended measures of sensitivity to musical pitch and examined whether performance on tests of tonal structure and pitch memory was related to, or dissociated from, performance on tests of nonmusical cognitive skills (standardized tests of cognitive abstraction, vocabulary, and memory for digits and nonrepresentational figures). Factor analyses of data from 100 neurologically intact Ss (aged 18–40 yrs) revealed a dissociation between music and nonmusic variables, both for the full data set and a set for which the possible contribution of levels of music training was statistically removed. A 40-yr-old female with neurological impairment scored within the range of matched controls on nonmusic tests but much lower than controls on music tests. It is concluded that this study provides further evidence of a functional specificity for musical pitch abilities. Examples of melodies and chord progressions are appended. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Mechanical properties of internally nitrided Fe−Ti and Fe−Cb alloys

Highly formable ferrous alloys containing Ti or Cb can be strengthened by a nitrogenation treatment which produces alloys containing dispersions of submicroscopic particles of TiN or CbN. By this treatment, the yield strength of alloys containing only 0.2 pct Ti or 0.3 pct Cb is increased from 105 to 700 MPa while retaining tensile elongations of 10 to 15 pct, good bendability, and good impact resistance. The CbN particles begin to coarsen at 600°C causing softening, a decrease in electrical resistivity, and an increase in impact resistance. The first response to annealing of the Fe−TiN system is a drop in resistivity which also begins at 600°C. Attending this change is an increase in hardness which continues to 800°C where the first precipitates become discernible by transmission electron microscopy. Subsequently, hardness falls as the particles grow to discs on {100} planes. The magnitude of the strengthening, its concentration dependence, and its response to heat treatment are adequately explained by a model which attributes initial resistance to dislocation motion to coherency strains set up by a distribution of very fine precipitates. With particle growth, strengthening first increases until at a critical particle size Orowan looping becomes dominant; thereafter softening occurs with further growth.     

Retropharyngeal pseudomeningocele after atlanto-occipital dislocation: report of two cases

OBJECTIVE AND IMPORTANCE: We report two cases of retropharyngeal pseudomeningocele after atlanto-occipital dislocation. This is rare, with only one other reported case in the literature. CLINICAL PRESENTATION: We report two patients who presented after blunt cervical and head trauma. Plain films revealed that each patient had atlanto-occipital dislocation. Subsequent magnetic resonance imaging revealed the delayed development of retropharyngeal pseudomeningocele. Concomitant hydrocephalus was noted in both patients. INTERVENTION: The surviving patient showed marked neurological improvement and resolution of his pseudomeningocele after ventriculoperitoneal shunting. CONCLUSION: For patients with closed head injuries who develop posttraumatic pseudomeningocele, we recommend cranial computed tomography to assess for the presence of hydrocephalus. In patients with atlanto-occipital dislocation, delayed neurological deterioration warrants magnetic resonance imaging of the craniocervical junction to rule out posttraumatic pseudomeningocele.     

Temporal contrast and the word frequency effect.

Studied the word frequency effect in recall and recognition under 3 list structures: (a) homogeneous rare or common nouns, (b) mixed alternating frequencies, and (c) mixed blocked frequencies. Exp I with 96 undergraduates found that the number of frequency contrasts within a list had a clear effect on recall and little effect on recognition. Recall of rare items was poor in a homogeneous list, equal to common items in a blocked list, and better than common items when in a list of alternating frequencies. Exp II with 48 Ss examined the reversed frequency effect of the alternating list under overt and covert rehearsal conditions across 3 trials. Under overt rehearsal there was no significant difference in number of rehearsals of rare and common items. The superior recall of rare items present on Trial 1 decreased across trials supporting a stimulus change-contrast interpretation of the effect of mixed frequency items in free recall. (French summary) (22 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Microstructures developed during thermomechanical treatment of HSLA steels

One purpose of thermomechanical treatment of steels, for example the control rolling of plate, is to produce the finest uniform microstructure in the product to optimize its strength and toughness. To achieve this end requires control of the structual changes that occur during reheating, high-temperature (roughing) deformation, lower temperature (finishing) deformation, and austenite transformation. A study has been made of the effects of the deformation processing variables on the microstructural changes that occur in high-strength low-alloy (HSLA) steels in the temperature ranges in which complete, partial, or no recrystallization occurs. The experimental technique comprised a sequence of plane-strain compressions of specimens being cooled at rates controlled to simulate the rate of cooling of slabs being rolled to plates. The results show that in the complete recrystallization range a fixed pass schedule refines the initial grain sizes in steels of a wide range of compositions and initial grain sizes to about the same final size; the final recrystallized grain size decreases with deformation temperature (within the complete recrystallization range), increasing strain rate, and increasing draft,i.e., with any deformation parameter that increases flow stress; the solute content and initial grain size, which are fixed by reheat temperature, control the temperature at which complete recrystallization stops during hot rolling. Deformation in the “partial recrystallization” range causes duplexing in the austenite that cannot be removed by subsequent rolling, consequently rolling in this range should be avoided. During finishing, the height of the flattened austenite grains decreases with increasing finishing reduction, but at a rate less than the rate of decrease of specimen height, indicating that some recovery is occuring. The grain diameter of the ferrite formed from fine, elongated austenite is about half the austenite grain-boundary separation (measured in the throughthickness direction) indicating that the elongated boundaries are the primary nucleation sites for ferrite.     

Expectancies generated by melodic intervals: evaluation of principles of melodic implication in a melody-completion task

Bottom-up principles of melodic implication (Narmour, 1990) were evaluated in a melody-completion task. One hundred subjects (50 low training; 50 high training in music) were presented each of eight melodic intervals. For each interval, the subjects were asked to compose a short melody on a piano keyboard, treating the interval provided as the first two notes of the melody. For each melody, the first response--the note immediately following the initial interval--was analyzed. Multinomial log linear analyses were conducted to assess the extent to which responses could be predicted by Narmour's (1990, 1992) bottom-up principles. Support was found for all of Narmour's principles, and two additional predictors based on implied tonal structure. Responses of low- and high-training groups were similar.