Journée de travail is more used to define an amount of work, whatever the weekday, like il faut encore une journée de travail pour terminer ce chantier or il se repose après sa journée de travail while jour ouvrable defines the days of the week during while regular work can legally be done.

The jours ouvrables span from Monday to Saturday (included) excluding holidays (jours fériés).

We also have the jours ouvrés that are like jour ouvrables but exclude Saturdays¹. Here ouvrables/ouvrés are not related to ouverts (open) but to are cognates of ouvrage, œuvre, opérer. (from the Latin opera).

Assuming you don’t work on Saturday mornings, you might use ouvrés with matin, but that’s rare and not colloquial. e.g.:

Sous-préfecture d’Apt
accueil sans rendez-vous tous les matins ouvrés entre 8h30 et 11h30

If your talk about generic workdays, alternatives are :

Les matins en semaine
Les matins de la semaine
Les matins de semaine

but in your case (the mornings of the days I go to work), better to say:

Les matins où je travaille
Les/mes matinées travaillées

¹ _{For most workplaces, Saturdays are excluded, but it is also possible for some of them to have jours ouvrés that include Saturdays but exclude Mondays.}