No, Access only supports joining by field value, not by expression. You can join subqueries, though:
SELECT ....
FROM (SELECT *, MID(t1.f1, 1, 13) KeyValue FROM T1) as t1
LEFT JOIN (SELECT *, MID(t2.f2, 1, 13) KeyValue FROM T2) as t2
ON t1.KeyValue = t2.KeyValue