What is a risk free portfolio?
Moreover, is it possible to construct a risk free portfolio?
Yes it is A possible to construct a portfolio of stocks that has an expected return equal to the risk-free rate. Such kind of portfolios are also called zero beta portfolio that have zero systematic risk.
Also know, what is a risk free security?
A security which is free of the various possible sources of risk. One is the risk that the debtor may default; this is thought to be absent in the case of UK, US, and many other countries' government debt.
A risk-free asset is one that has a certain future return—and virtually no possibility of loss. Debt obligations issued by the U.S. Department of the Treasury (bonds, notes, and especially Treasury bills) are considered to be risk-free because the "full faith and credit" of the U.S. government backs them.