answer:
raising temperature to 180c reduces the temperature thereby reducing overall strength and also hardness.
lengthening the time at 150c to 5 days also does the same
Step-by-step explanation:
The optimum timing for Age hardening is 22 hours for 150°c
when we increase the materials temperature to 180°c we have it that overall strength and hardness would reduce. this is due to some precipitates that would grow exponentially as some other nuclei will then shrink or maybe disappear. This effect causes a decrease in strength or hardness.
This is also applicable to lengthening the time of aging at 150c
When we decrease the time of ageing, it causes inappropriate growth of nuclei. more numbers of boundaries will be causing lower strength and hardness.