Heat treatment of cold-sprayed C355 Al for repair: microstructure and mechanical properties

Cold gas dynamic spraying of commercially pure aluminum is widely used for dimensional repair in the aerospace sector as it is capable of producing oxide-free deposits of hundreds of micrometer thickness with strong bonding to the substrate, based on adhesive pull-off tests, and often with enhanced hardness compared to the powder prior to spraying. There is significant interest in extending this application to structural, load-bearing repairs. Particularly, in the case of high-strength aluminum alloys, cold spray deposits can exhibit high levels of porosity and microcracks, leading to mechanical properties that are inadequate for most load-bearing applications. Here, heat treatment was investigated as a potential means of improving the properties of cold-sprayed coatings from Al alloy C355. Coatings produced with process conditions of 500 °C and 60 bar were heat-treated at 175, 200, 225, 250 °C for 4 h in air, and the evolution of the microstructure and microhardness was analyzed. Heat treatment at 225 and 250 °C revealed a decreased porosity (~ 0.14% and 0.02%, respectively) with the former yielding slightly reduced hardness (105 versus 130 HV0.05 as-sprayed). Compressive residual stress levels were approximately halved at all depths into the coating after heat treatment, and tensile testing showed an improvement in ductility

Microstructural evolution in solution heat treatment of gas- atomised Al alloy (7075) powder for cold spray

Cold gas dynamic spray is being explored as a repair technique for high-value metallic components, given its potential to produce pore and oxide-free deposits of between several micrometers and several millimeters thick with good levels of adhesion and mechanical strength. However, feedstock powders for cold spray experience rapid solidification if manufactured by gas atomization and hence can exhibit non-equilibrium microstructures and localized segregation of alloying elements. Here, we used sealed quartz tube solution heat treatment of a precipitation hardenable 7075 aluminum alloy feedstock to yield a consistent and homogeneous powder phase composition and microstructure prior to cold spraying, aiming for a more controllable heat treatment response of the cold spray deposits. It was shown that the dendritic microstructure and solute segregation in the gas-atomized powders were altered, such that the heat-treated powder exhibits a homogeneous distribution of solute atoms. Micro-indentation testing revealed that the heat-treated powder exhibited a mean hardness decrease of nearly 25% compared to the as received powder. Deformation of the powder particles was enhanced by heat treatment, resulting in an improved coating with higher thickness (* 300 lm compared to * 40 um for untreated feedstock). Improved particle–substrate bonding was evidenced by formation of jets at the particle boundaries

Validity of a Farsi translation of the composite International Diagnostic Interview (CIDI) to diagnose schizophrenia and bipolar disorder

Background: The Composite International Diagnostic Interview (CIDI) is a comprehensive, standardized diagnostic interview for the assessment of psychiatric disorders. There have been few studies on the validity of the CIDI. The objective of present study was to assess the validity of a Farsi translation of the complete CIDI and its psychosis/mania module in five referral clinical psychiatric settings. Methods: Two hundred and three as well as 104 consecutive admissions were interviewed using the complete and the psychosis/mania module, respectively. Within two days of the CIDI interview, two last year residents of psychiatry or psychiatrist who were blind to the CIDI diagnosis completed the Clinical diagnostic checklists (based on DSM-IV and ICD-10 criteria) simultaneously and reached the consensus diagnosis. Data analysis was performed using SPSS 11 to determine the validity of CIDI. Results: The sensitivity and specificity for the diagnosis of schizophrenia was 0.12 and 0.96 using DSM-IV criteria. According to ICD-10 criteria, the results were the same with 0.19% sensitivity and 0.96% specificity. The sensitivity for the diagnosis of bipolar I disorder was low (0.21 using DSM-IV criteria and 0.17% using ICD-10) and specificity, high (0.90 compared to DSM-IV and 0.89 compared to ICD-10 criteria). The results were rather similar for the psychosis/mania module of CIDI. Conclusion: This study suggests that the Farsi translation of both the complete CIDI and the psychosis/mania module of CIDI have good specificity, but poor sensitivity for the diagnosis of schizophrenia and of bipolar I disorder