Companies have issued record volumes of junk bonds in recent years, spurred by low interest rates and a wave of leveraged buyouts. And yield-hungry investors were snapping up the riskier debt...... Default for most investors means big losses, a function of industry problems or economic downturn. But among Wall Street's restructuring advisors, bad times mean good business..... Poised to rise A strong economy and the lowest interest rates in decades pushed default rates for non-investment grade, or junk bonds down to 1.25 percent last year -- a seven-year low and below the historic 5 percent average...... But banks noted that...