The U.S. Commerce Department has announced that it will investigate whether aluminum extrusion parts from China are being unfairly subsidized and dumped into the U.S. market.   Brief statement from Alliance for American Manufacturing (AAM) Executive Director Scott Paul:   "China should substantially appreciate its currency.  It's imperative for the Administration and Congress to ensure a level playing field for American workers and businesses.  To that end, we're hopeful that the Administration will ultimately consider China's currency manipulation to be a countervailable subsidy in this case and others.  Otherwise, more Americans may face layoffs because of China's failure to honor its trade commitments."