Two Alexandria police officers testified yesterday they believed Public Safety Director Charles T. Strobel torpedoed their careers because they pressed for an internal investigation of one of his top aides.

Investigator Joseph Morrash and officer Morton Ford took the stand yesterday in U.S. District Court in Alexandria in a lawsuit that seeks to prove that Strobel violated their constitutional rights by transferring them to other duties after they helped in the investigation. The two officers are seeking a total of $500,000 in damages.

Both men said they were given patrol duties and removed from the Alexandria force's investigative staff after they called for an investigation of Lt. John Stedman, then head of the department's internal affairs section. The allegations by the two officers against Strobel were considered and rejected earlier this year by a special grand jury.

Strobel's lawyers argued yesterday that Strobel, who is also Alexandria's police chief, was within his rights to transfer his employes. If the workers believed the changes were punitive, they should appeal through the city's grievance process, the lawyers said, urging District Judge Richard L. Williams to dismiss the case.

The trial, expected to conclude today, centers on an incident in mid-July l983 when Ford reported allegations against Stedman. An investigation by Strobel and a second one by the Alexandria Police Association failed to confirm the allegations, several witnesses testified yesterday.

Ford testified that shortly after he raised the allegations and suggested they be investigated, he was transferred. Shortly after Strobel learned of the association's separate investigation, Morrash said he was transferred to a patrol beat.