What should I use for consequent AES key derivation?
Yes, generally you can use a hash as a "poor man's KDF". For instance, look at the Q/A about KDF1 and KDF2 which are little more than glorified hash functions. Of course, as e-sushi noted, the theoretical requirements of a KDF is a little bit higher than those required of a hash.

Some differences:


A KDF doesn't have just one input; besides the Input Keying Material it may also have inputs such as Info containing e.g. a label for the key, a salt and the length of output material to generate;
The inputs of the KDF should be canonically encoded or there may be restrictions on the input parameter so that different input combinations will never generate the same output;
The output of many KDF's is configurable and may extend the output size of the underlying hash function or block cipher (depending if the KDF supports expansion);
The output of the KDF is generally well defined, usually if you want to take 128 bits from a 256 bit hash you take the leftmost bits, but a KDF will have formalized what output should be taken (and yes, I've seen weird / stupid ones);
The output of the KDF should be full randomized, which is theoretically not a requirement for hash functions.


Now e.g. SHA-256 or SHA-512 will have output that is indistinguishable from random, so the last point is mostly theoretical in nature. All the other differences can be ignored or implemented in your own hash function. So yes, it is possible to define your own KDF. 

However, I'd suggest you use KDF1 so you'd at least be compliant to an existing KDF where all these design choices are already made. KDF1 is very basic and doens't seem to offer canonical encoding, so you  may want to make sure that OtherInfo has a static size. In the end, you'd still be left with a single call to a hash. A HMAC based KDF such as HKDF would be considered more secure, of course, as there are few primitives that match a PRF such as HMAC with regards to resilience.