热机械处理对Ti-45Al-5Nb-0.3Y合金的显微组织与力学性能的影响

EFFECTS OF THERMO-MECHANICAL TREATMENT ON MICROSTRUCTURE AND MECHANICAL PROPERTY OF Ti-45Al-5Nb-0.3Y ALLOY

包套锻造Ti-45Al一5Nb-0.3Y合金由大量细小的动态再结晶等轴,γ晶粒(晶粒尺寸可达1—2μm)、弯曲或破碎的层片和少量的残余平直层片组成,变形组织含有大量位错及少量变形孪晶,锻态试样抗拉强度(σb)、延伸率(δ)分别达到708.1 MPa和0.95%.再通过不同的热处理分别得到品粒细小的双态组织、近层片组织和全层片组织,经1320℃/30 min炉冷后得到双态组织,层片晶粒尺寸(d_1)约为20μm,层片体积分数((?)1)约为60%,具有最高的δ,约为1.9%,σ_b约为658.9 MPa,为穿晶和沿晶混合断裂;经1340℃/30 min炉冷后得到近层片组织,d_1约为60μm,(?)1约为95%,σ_b约为690.2 MPa,δ约为1.75%,主要为穿晶(层片)断裂;经1370℃/15 min炉冷后得到细小全层片组织(d_1约为40μm),具有最高的σ_b,约为715.1 MPa,δ约为1.51%,为穿晶断裂。

As forged Ti- 45Al-5Nb-0.3Y alloy is composed of a large number of dynamicly recrystallized （DRX） 7 grains with sizes of 1-2μm, curved or broken lamellae, and a small amount of remnant lamellaes. The deformed regions contained lots of dislocations and a little deformation twinnings. The ultimate tensile strength （σb） of as forged alloy is about 708.1 MPa and the elongation （5） is about 0.95%. The fine duplex （DP）, near lamellar （NL） and fully lamellar （FL） microstructures were obtained by further heat treatments. The DP microstructure with lamellar colony size （dl） of about 20 μm and lamellar volume fraction （φ1） of about 60% was obtained by heat treatment of 1320 ℃/30 min/FC, which exhibited the highest 5 of about 1.9% and σb of about 658.9 MPa, and showed the transgranular and intergranular cracks. The NL microstructure with d1 of about 60 μm and φ1 of about 95% was obtained by heat treatment of 1340 ℃/30 min/FC, which exhibited 5 of about 1.75% and σb of about 690.2 MPa correspondingly and mainly showed the transgranular cracks. The FL microstructure with d1 of about 40 μm was obtained by heat treatment of 1370 ℃/15 min/FC, which exhibited 5 of about 1.51% and the highest σb of about 715.1 MPa and showed the transgranular cracks.