Abstract: The microstructure and the mechanical properties from room temperature up to 1050℃ of Ni_3Al alloys containing 0—0.6 at.-%Zr,0—7.7 at.-%Cr and 0—2.22 at.-%B have been studied.It was found that the temperature dependence of their yield strength variation reveals to be anomalous,i.e.the strength increases with the temperature raising,and then decreases till it surpassed the peak value.Both Zr and Zr+Cr may improve the yield strength of the al- loys in the entire range of testing temperatures,as well as the tensile strength and elongation under high temperatures.B is favourable to raise the tensile and yield strengths of the alloys, and also plasticity.But the strength will reduce as B added is over 2.22 at.-%.The Ni_(20)Al_3B_6 and Ni_3Al eutectic mixture like islands and globes precipitated inside the grains and along the grain bounderies,which are harmful to the strength and ductility,may be formed when the B content exceeds the limit of solubility.

Key words: Ni_3Al, microstructure, mechanical property, yield strength