Investigation of Microstructure and Stress Corrosion Cracking in Al-6061-T6 Alloy at Different Loads

Stress corrosion cracking (SCC) refers to the damage of mechanical components which are under the combined action of static load and corrosive environment. This phenomenon occurs in various applications including naval and aerospace industry where aluminum and steel alloys experience mechanical loadings in the presence of corrosive environments. In this research work, microstructural and environmental influence on corrosion behavior of Al-6061-T6 at different static loads was investigated. A new test fixture was developed for stress corrosion cracking. Dog-bone shaped tensile specimens of Al-6061-T6 were manufactured using CNC milling machine. Tests were conducted at constant loads of 200 N, 500 N and 800 N, in three different environments: dry ambient conditions, distilled water and 3.5% NaCl solution. Testing continued for different intervals of time i.e. 96 hours, 68 hours and 4.5 hours respectively. After each set of experiments, specimens were observed for cracks using metallurgical microscope. Detailed fractographic investigation of all the tested specimens was carried out using Scanning Electron Microscope (SEM). Excessive corrosion and material degradation was observed in specimens tested in distilled water and 3.5% NaCl environments. Microstructural analysis depicted pitting corrosion and crack deformation.  Some regions clearly showed that grain boundaries were attacked due to oxidation and chemical attack causing weakening of grain boundaries and resulted into intergranular corrosion. Precipitates and grain boundaries in Al-6061-T6 served as a reason of crack initiation due to hydrogen diffusion. Fractographic investigation provided the evidence of trans granular fracture as well as intergranular fracture which was observed as dimples and extensive ductile tearing.

Effects of Nuisance Dust Total on Health of Workers of Textile Sector in Punjab Pakistan

This study focused to evaluate effect of cotton dust and PM2.5 on health of workers of textile sector in Punjab. Prevalence of Chronic Obstructive Pulmonary Disease (COPD) was estimated in this study. This cross sectional study has also shown reduced pulmonary function in association to workplace exposure to cotton dust and PM2.5. Subjects with cough, phlegm, chronic bronchitis and occupation related wheeze had significantly impaired pulmonary function indices. This study also indicates additive effect of smoking with cotton dust and PM2.5 resulting into decline in lung function indices. Workers in stitching section, with prolonged duration of work, were more inclined to developing one or more of the respiratory disorders. In order to control occupational pulmonary diseases in the textile sector, effective control measures pertaining to dusts, repeated awareness of workers and staff on the issues of workplace hazards, and continuous health surveillance and monitoring programs is suggested and needed to be implemented. The utilization of proper personal protective equipment for workers at workplace is mandatory. Ventilation in the workplace, capacity building about workplace hazards and periodic medical check-up of workers in cotton processing facilities are effective tools to workplace exposure.