A control valve comprising: a valve body (90; 390) having a fluid inlet conduit (10; 310) terminating at a fluid inlet orifice (12; 312) and a fluid outlet conduit (14; 314) commencing at a fluid outlet orifice; a valve seat (20; 320) defined at one of the fluid inlet orifice (12; 312) and the fluid outlet orifice; a valve housing body (62; 362) secured to the valve body (90; 390); a valve chamber sealing diaphragm (70; 370) having an actuator side and having a valve chamber side, the valve chamber sealing diaphragm (70; 370) being in sealing engagement with the valve housing body (62; 362) at an outer periphery of the valve chamber sealing diaphragm (70; 370), the valve body (90; 390), the valve housing body (62; 362), and the valve chamber sealing diaphragm (70; 370) cooperating to define a valve chamber (50; 350), the valve chamber sealing diaphragm (70, 370) further comprising a control element (80, 380) attached to the valve chamber sealing diaphragm (70, 370) at an inner periphery of the valve chamber sealing diaphragm (70, 370), the control element (80, 380) having a control surface (81, 381) offset from the valve chamber side of the valve chamber sealing diaphragm (70, 370); and the control surface (81, 381) being configured to selectively engage the valve seat (20; 320), wherein one of: i. the valve chamber side of the valve chamber sealing diaphragm has a plastically deformed concentric strain hardened region having a concave shape formed between 1/3 and 2/3 of a distance between the inner periphery of the valve chamber sealing diaphragm and the outer periphery of the valve chamber sealing diaphragm biasing the control surface away from the valve seat, the control valve being a normally open control valve; or ii. the actuator side of the valve chamber sealing diaphragm has a plastically deformed concentric strain hardened region having a concave shape formed between 1/3 and 2/3 of a distance between the inner periphery of the valve chamber sealing diaphragm and the outer periphery of the valve chamber sealing diaphragm biasing the control surface toward the valve seat, the control valve being a normally closed control valve, and wherein the control element (80, 380), the valve chamber sealing diaphragm (70, 370), and the valve housing body (62, 362) are machined from a single piece of material. a valve body (90; 390) having a fluid inlet conduit (10; 310) terminating at a fluid inlet orifice (12; 312) and a fluid outlet conduit (14; 314) commencing at a fluid outlet orifice; a valve seat (20; 320) defined at one of the fluid inlet orifice (12; 312) and the fluid outlet orifice; a valve housing body (62; 362) secured to the valve body (90; 390); a valve chamber sealing diaphragm (70; 370) having an actuator side and having a valve chamber side, the valve chamber sealing diaphragm (70; 370) being in sealing engagement with the valve housing body (62; 362) at an outer periphery of the valve chamber sealing diaphragm (70; 370), the valve body (90; 390), the valve housing body (62; 362), and the valve chamber sealing diaphragm (70; 370) cooperating to define a valve chamber (50; 350), the valve chamber sealing diaphragm (70, 370) further comprising a control element (80, 380) attached to the valve chamber sealing diaphragm (70, 370) at an inner periphery of the valve chamber sealing diaphragm (70, 370), the control element (80, 380) having a control surface (81, 381) offset from the valve chamber side of the valve chamber sealing diaphragm (70, 370); and the control surface (81, 381) being configured to selectively engage the valve seat (20; 320), wherein one of: i. the valve chamber side of the valve chamber sealing diaphragm has a plastically deformed concentric strain hardened region having a concave shape formed between 1/3 and 2/3 of a distance between the inner periphery of the valve chamber sealing diaphragm and the outer periphery of the valve chamber sealing diaphragm biasing the control surface away from the valve seat, the control valve being a normally open control valve; or ii. the actuator side of the valve chamber sealing diaphragm has a plastically deformed concentric strain hardened region having a concave shape formed between 1/3 and 2/3 of a distance between the inner periphery of the valve chamber sealing diaphragm and the outer periphery of the valve chamber sealing diaphragm biasing the control surface toward the valve seat, the control valve being a normally closed control valve, i. the valve chamber side of the valve chamber sealing diaphragm has a plastically deformed concentric strain hardened region having a concave shape formed between 1/3 and 2/3 of a distance between the inner periphery of the valve chamber sealing diaphragm and the outer periphery of the valve chamber sealing diaphragm biasing the control surface away from the valve seat, the control valve being a normally open control valve; or ii. the actuator side of the valve chamber sealing diaphragm has a plastically deformed concentric strain hardened region having a concave shape formed between 1/3 and 2/3 of a distance between the inner periphery of the valve chamber sealing diaphragm and the outer periphery of the valve chamber sealing diaphragm biasing the control surface toward the valve seat, the control valve being a normally closed control valve, and wherein the control element (80, 380), the valve chamber sealing diaphragm (70, 370), and the valve housing body (62, 362) are machined from a single piece of material.