Microstructural evolution of a delta containing nickel-base superalloy during heat treatment and isothermal forging

The next generation of aerospace gas turbine engines need to operate at higher temperatures and stresses to improve their efficiency and reduce emissions. These operating conditions are beyond the capability of existing nickel-base superalloys, requiring the development of new high temperature materials. Controlling the microstructures of these new materials is key to obtaining the required properties and, therefore, it is critical to understand how these alloys respond to processing and heat treatment. Here, the microstructural evolution of V207M, a new δ containing, nickel-base superalloy, has been investigated following heat treatment and forging. The solvus temperatures of the γ′ and δ phases, determined by differential scanning calorimetry and microscopy, were found to be ~985 and ~1060 °C respectively. Isothermal forging of the alloy was conducted at 1000, 1050 and 1100 °C, corresponding to different volume fractions of retained δ. Considerable softening was observed prior to steady state flow when forging at 1000 °C, whilst only steady state flow occurred at 1050 and 1100 °C. The steady state flow process was believed to be dominated by dynamic recovery in the γ phase, with an activation energy of 407 kJmol−1. Samples that exhibited flow softening also showed a significant change in the orientation of the δ precipitates, preferentially aligning normal to the forging axis, and this reorientation was thought to be the cause of the observed flow softening

Thermal activation of fatigue crack growth: analysing the mechanisms of fatigue crack propagation in superalloys

A method for deriving apparent activation energies, Eapp, for fatigue crack growth (FCG) is presented. It is shown how these Eapp values can be used to analyse the main underlying mechanism causing the progression of the crack. The Eapp values for fatigue crack growth in air and vacuum, and with and without a dwell are obtained for a range of Ni based superalloys for turbine disc applications. The apparent activation energies range from about zero to about 300kJ/mol. The analysis allows identification of alloys that are prone to FCG through diffusion controlled mechanisms, notably grain boundary oxidation or grain boundary creep, as well as alloys that are nearly immune to FCG by grain boundary oxidation or creep

Relationship of probable ADHD with novelty seeking, severity of psychopathology and borderline personality disorder in a sample of patients with opioid use disorder

OBJECTIVE The aim of the present study was to evaluate the relationship of probable attention-deficit hyperactivity disorder (ADHD) with novelty seeking (NS), the severity of psychopathology and borderline personality disorder (BPD) in a sample of male patients with opioid use disorder (OUD). METHODS Participants included 229 patients with OUD. Participants were evaluated with the Adult ADHD Self-Report Scale (ASRS-v1.1), the Symptom Checklist-90-Revised (SCL-90-R) and NS subscale of the Temperament and Character Inventory (TCI). In addition, BPD was assessed with the Structured Clinical Interview for DSM-III-R-Personality Disorders (SCID-II). RESULTS Age, duration of education, marital and employment status did not differ between those with probable ADHD (n = 54, 23.1%) and those without (n = 175, 76.9%). The severity of psychopathology, NS and subdimensions (other than NS1, which was lower) were higher among those with the probable ADHD. ADHD scores were midly correlated with NS scores, other than NS1. In logistic regression analyses, the severity of NS, particularly Impulsiveness (NS2), together with general psychopathology, predicted probable ADHD, whereas the presence of BPD had no effect. CONCLUSIONS These findings suggest that trait impulsivity, together with the severity of psychopathology, is related with the probable ADHD, while the presence of BPD has no effect among adult patients with OUD