Easton states their cf riser bar has the highest impact strength of ANY riser bar. It's not just my opinion... They actually yield elastically quite a bit (vibration absorbtion), but there is no plastic region where permanent deformation occurs. It takes a lot more to break a cf bar than a 7000 series Alum Bar, so in the instances where cf bars fracture, you can bet an alum bar would have failed as well.
7000 series Aluminum does NOT yield much at all before it fractures (elastic or plastic), and it will fail at significantly lower forces than cf. It is stronger than 6000 series, but more brittle
6000 series will yield more before fracture, but will generally start yielding at lower forces than 7000, 6000 is used because it is inexpensive and easily welded, which is why most frames are made out of it. It is not considered a high strength alloy.
Some bars are made of 2000 series Alum. My Deity bars are made of 2014, but weigh 325g, maybe 50g more than a 7000 series bar needs to be to have the same yield stregnth. This is because these bars will bend A LOT compared to others before fracture. So, I have an extra 50g on my bike because I wanted bars that will bend before they break. They are a dh bar, so it'll still take a lot to bend them. This alloy is a lot stronger than 6061, and is commonly use for Aircraft Frames.
Tensile strenght of 6061 is about 115 MPa, cf ranges from about 250 - 350 Mpa, both are forces required to fracture the material, however plastic yielding (bending) occurs at only 48 MPa for 6061. 2014 and 7075 take about 1/3 more force to bend, 7075 is a bit stronger than 2014.