Australian shipbuilder Austal on Monday night Eastern Time said its board has given approval to Hanwha Defense USA to conduct due diligence related to a non-binding offer to acquire the company’s U.S. operations for up to $1.2 billion. Hanwha Defense USA on Monday evening released a statement that its preliminary, non-binding offer for Austal USA is “contingent on due diligence that permits a thorough evaluation of Austal USA’s operations and financials, including newly disclosed information.” In the Aug. 11—Australian time—market…