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 Cable Television on Women in Pakistan: A Comparative Study of Heavy and Light Viewers in Lahore

This study investigates the “effects of cable television on the life patterns of women in Lahore, Pakistan” through survey using interviews’ schedule as a tool of data collection. It targeted 432 women aged 18-40 years and viewing cable television for a minimum two years. The study recorded the respondent’s consumption patterns, level of viewing, preferred channels and programs, favorite watching time, control over remote and restrictions on viewing. It crossed checked the above factors with the level of viewing alongwith demographic characteristics of the respondents. The major hypothesis studied was “greater the exposure to cable television greater the impact on the lives of women.” The sub-hypothesis included ‘heavy viewers have greater effect on their activities, family and social interaction patterns, cultural practices, domestic and personal expenditure, and they are more influenced by the television characters especially depicting western and urban Indian women than the moderate and light viewers. The data was analyzed through univariate and bivariate statistical procedures and the results are presented in two categories: i.e. general and major findings of hypothesis testing. The general findings revealed that the majority of respondents were aged 31 to 40 years, belonged to the middle and upper middle class, were graduates but unemployed, and were heavy viewers. Majority respondents had cable connection for the last two years, indicating increasing popularity of cable television in Lahore, also making it the main source of entertainment. There is no link between demographic characteristics and consumption patterns. However, the respondents complained that men had more rights to watch cable television than women. The statistical test chi-square was applied for testing the hypothesis, confirming that ‘greater the exposure to cable television greater the effect on the lives of women’. It confirmed that heavy viewing affected household and other activities of the women like newspaper reading, going to cinema, the meals cooking and serving schedule, their domestic or personal expenditure and interaction with friends or and relatives. They were prone to accepting the role, culture and lifestyle of western and Indian women watched on the cable channels. The study also identified a few areas for future researchers and made recommendations towards their improvement.