On June 25, 1940, the United States Patent and Trademark Office awarded patent 2,205,854 for Kroll's method of manufacturing titanium and alloys thereof, filed on July 6, 1938. On December 4, 1940, Kroll applied for US citizenship. He worked as a consulting engineer for Union Carbide Research Laboratories at Niagara Falls, New York. As the US declared war on the Axis nations in December 1941, Kroll's patent was forfeited by the US government as falling under the Alien Property Custodian act prompting a seven-year litigation, ending in favor of William Kroll, though litigation fees of over $1 million ate up the compensation awarded. Slowly the US government and the industry began to recognize the potential of titanium. The US government established a research center in Boulder, Colorado in 1944, and in late 1948, Dupont de Nemours began the commercial production of titanium using the Kroll process. Meanwhile, Kroll's focus had turned to zirconium. He became a consulting metallurgist to the United States, Department of the Interior, Bureau of Mines in 1945 at their research facility at Albany, Oregon. The first zirconium strip was rolled out there in August 1946. In 1951, William Kroll joined the Oregon State University, established a non-profit Metal Research Foundation awarding scholarships and grants in the USA and in Europe.