微量硼对Ti-Fe-Cu-Sn-Nb合金力学性能的影响

Effect of minor boron on mechanical properties of Ti-Fe-Cu-Sn-Nb alloys

基于细晶强化和第二相强化原理,通过在一种近β钛合金中加入微量硼(B)元素,以强化该合金。首先设计不同含硼量的Ti_(85)Fe_(6)Cu_(5)Sn_(2)Nb_(2)合金,并用真空非自耗电弧炉制备,随后对合金在800℃下进行多道次热轧及最终淬火。通过组织观察、拉伸力学性能测试、断口观察及透射电子显微分析,考察不同硼含量对Ti_(85)Fe_(6)Cu_(5)Sn_(2)Nb_(2)合金组织及力学性能的影响。结果表明,微量硼元素可以使合金的晶粒细化,强度明显提高,但伴随着塑性下降。添加质量分数为0.15%硼可以使合金具有较好的综合力学性能(σ_(0.2)=1105 MPa,δ_(b)=4.5%)。随着硼含量的增加,合金的强度升高,最高可达115_(6)MPa。硼的加入在合金中形成正交结构的TiB相,分布于β钛基体中。变形过程中,TiB断裂、TiB割裂基体及其与基体脱粘,产生裂纹源,导致合金塑性下降。

Based on grain refinement and secondary phase strengthening,minor boron(B)was added to nearβ-Ti alloy to strengthen the alloys.Ti_(85)Fe_(6)Cu_(5)Sn_(2)Nb_(2)alloys with various B contents were designed,prepared by using a non-consumable vacuum arc melting furnace,and hot rolled at 800℃followed by quenching.The effects of minor B addition on the microstructure and mechanical properties of Ti_(85)Fe_(6)Cu_(5)Sn_(2)Nb_(2)alloy were investigated through microstructure observation,tensile mechanical test,fracture observation and transmit electron microscopy.The results reveal that minor B addition can refine the grains,improve the strength whereas the plasticity of the alloy is decreased.The alloy containing 0.15%(mass fraction)B possesses the better comprehensive mechanical properties(σ_(0.2)=1105 MPa,δ_(b)=4.5%).With the increase of B content,the strength of the alloy is increased and reaches up to 115_(6)MPa.Orthorhombic TiB compounds are formed in the alloy,distributed in theβ-Tialloy matrix.Upon deformation,the fracture of TiB phases,cutting and debonding of TiB phases to the alloy matrix,formed the fracture source,resulted in the decrease of the alloy plasticity.