These investment-grade debt-relate ETFs attracted heavy inflows as investors turned to safer plays in a volatile market. However, with the stock market picking up and risk aversion dissipating, fixed-income investors are shifting back into riskier debt.

Among the most popular ETF plays over the past week, the SPDR Barclays High Yield Bond ETF (NYSEArca: JNK) brought in $968.7 million, iShares iBoxx $ High Yield Corporate Bond ETF (NYSEArca: HYG) saw $644.9 million in flows and iShares J.P. Morgan USD Emerging Markets Bond ETF (NYSEArca: EMB) added $504.3 million, according to ETF.com.

Investors may be attracted to the cheap valuations and wider yield premiums that these bonds offer over safe-haven government bonds after benchmark yields on 10-year Treasuries dipped back toward all-time lows. Moreover, the rebound in energy prices could have reassured investor fears of a potential defaults in the energy space. JNK has a 7.64% 30-day SEC yield and HYG shows a 8.05% 30-day SEC yield. [Junk Bond ETFs are Hot Again]

In the same vein, investors who are looking for some value in the bond market may want to take a look at emerging market debt where yields also show a widening premium over government debt. EMB has a 5.44% 30-day SEC yield. [A Bond ETF Segment That Offers Attractive Value]