Monel K-500合金具有优异的耐腐蚀性能和良好的力学性能，被广泛应用于化工、船舶等领域。为研究定向凝固(DS)与固态相变双联协控技术对合金力学性能的作用机制，在不同生长速率下采用定向凝固和双联协控技术制备了Monel K-500合金，并对合金的微观组织和拉伸性能进行了分析。结果表明，定向凝固条件下合金的微观组织由γ相枝晶构成。当生长速率由100 μm/s减小至5 μm/s时，DS合金凝固时的温度梯度增大，在生长速率和温度梯度共同影响下枝晶组织逐渐粗化，合金中Cu元素偏析减弱且γ相织构强度增大，合金屈服强度与抗拉强度分别从248和421 MPa提高至288和487 MPa，延伸率由63.4%增大至69.9%。定向凝固与固态相变双联协控条件下，γʹ沉淀强化相析出，且微观偏析进一步减弱。随着生长速率减小，双联协控合金的屈服强度与抗拉强度增大，延伸率先减小后增大，裂纹由穿晶与沿晶混合扩展模式转变为以穿晶为主的扩展模式。断裂后合金中γ相晶体取向分析表明，合金中与择优生长方向<001>取向不一致的杂晶会引起晶粒内位错密度增大，从而导致合金延伸率降低。而晶粒细化有利于合金变形过程中应力的均匀分布，提高合金延伸率。相比于定向凝固，生长速率为5 μm/s时，双联协控合金的屈服强度与抗拉强度分别提高了34%和41%。

Monel K-500 alloy is a Ni-based alloy that is widely used in marine environments and chemical industries because of its exceptional corrosion resistance and mechanical properties. The synergetic modulation of directional solidification and thermal processing (DS-TP) technique combines DS and in situ heat treatment in a single experiment, thus eliminating the influence of environmental changes and avoiding aging effect. To investigate the effect of the DS-TP technique on the mechanical properties of the alloy, samples were prepared using DS alone and the DS-TP technique at different growth rates. Subsequently, the microstructures and mechanical properties of the samples were analyzed. In the DS experiments, an Al₂O₃ ceramic crucible (diameter: 10 mm) containing the alloy sample was heated using a graphite heater and an electromagnetic induction coil. As the sample was superheated to 200 K, it was immersed in the Ga-In-Sn liquid at a certain pulling rate. In the DS-TP experiments, the directionally solidified sample was in situ annealed at 1223 K for 1 h and then immersed into the liquid. Subsequently, the sample was subjected to an aging process at 923 K for 5 h. The microstructure of the directionally solidified Monel K-500 alloy showed columnar γ grains with pronounced <001> texture. When the growth rate decreased, the temperature gradient at the solid-liquid interface during directional solidification increased. Lower growth rates led to a coarser microstructure, lesser microsegregation of Cu, and fewer transverse grain boundaries. As the growth rate decreased from 100 μm/s to 5 μm/s, the yield strength, tensile strength, and elongation increased from 248 MPa, 421 MPa, and 63.4% to 288 MPa, 487 MPa, and 69.9%, respectively. Unlike the case of the directionally solidified alloys, the nanoscale γʹ hardening phase precipitated in the DS-TP-treated alloys and the degree of microsegregation decreased. Further, the yield strength and tensile strength increased from 368 and 640 MPa, respectively, to 386 and 686 MPa, respectively, as the growth rate decreased from 100 μm/s to 5 μm/s. The distribution of intergranular cracks in the fractography was similar to that of large-angle grain boundaries in the region closing the fracture. With the growth rate decreasing, intragranular cracks gradually appeared, and the number of intergranular cracks decreased. Moreover, grain deviation from the preferred growth orientation increased the dislocation density and decreased the elongation. Grain refinement promoted the homogeneous distribution of dislocations and caused a slight increase in the elongation. At a growth rate of 5 μm/s, the tensile strength and yield strength of the DS-TP-treated alloy increased by 34% and 41%, respectively.